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• What are some ways to accomplish a dynamic array?

  - by Ted

  I'm going to start working on a new game and one of the things I'd like to accomplish is a dynamic array sort of system that would hold map data. The game will be top-down 2d and made with XNA 4.0 and C#. You will begin in a randomized area which will essentially be tile based. As such a 2 dimensional array would be one way to accomplish this by holding numerical values which would correspond to a list of textures and that would be how it would draw this randomly created map. The problem is I would kind of only like to create the area around where you start and they could venture in which ever direction they wanted to. This would mean I'd have to populate the map array with more randomized data in the direction they go. I could make a really large array and use the center of it and the rest would be in anticipation of new content to be made, but that just seems very inefficient. I suppose when they start a new game I could have a one time map creation process that would go through and create a large randomly generated map array, but holding all of in memory at all times seems also inefficient. Perhaps if there was a way that I'd only hold parts of that map data in memory at one time and somehow not hold the rest in memory. In the end I only need to have a chunk of the map somewhat close to them in memory so perhaps some of you might have suggestions on good ways to approach this kind of randomized map and dynamic array problem. It wouldn't need to be a dynamic array type of thing if I made it so that it pulled in map data nearby that is needed and then once off the screen and not needed it could somehow get rid of that memory that way I wouldn't have a huge array taking up a bunch of memory.

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• An increase to 3 Gig of RAM slows down Ubuntu 10.04 LTS

  - by williepabon

  I have Ubuntu 10.04 running from an external hard drive (installed on an enclosure) connected via USB port. Like a month or so ago, I increased RAM on my pc from 2 Gigs to 3 Gigs. This resulted on extremely long boot times and slow application loads. While I was understanding the nature of my problem, I posted various threads on this forum ( Questions # 188417, 188801), where I was advised to gather speed tests, and other info on my machine. I was also suggested that I might have problems with the RAM installed. Initially, I did not consider that possibility because: 1) I did a memory test with a diagnostic program from DELL (My pc is from Dell) 2) My pc works fine with Windows XP (the default OS), no problems with memory 3) My pc works fine when booting with Ubuntu 10.10 memory stick, no speed problems 4) My pc works fine when booting with Ubuntu 11.10 memory stick, no speed problems Anyway, I performed the memory tests suggested. But before doing it, and to check out any possibility of hardware issues on the hard drive, I did the following: (1) purchased a new hard drive enclosure and moved my hard drive to it, (2) purchased a new USB cable and used it to connect my hard drive/enclosure setup to a different USB port on my pc. Then, I performed speed tests with 1 Gig, 2 Gigs and 3 Gigs of RAM with my Ubuntu 10.04 OS. Ubuntu 10.04 worked well when booted with 1 Gig or 2 Gigs of RAM. When I increased to 3 Gigs, it slowed down to a crawl. I can't understand the relationship between an increase of 1 Gig and the effect it has in Ubuntu 10.04. This doesn't happen with Ubuntu 10.10 and 11.10. Unfortunately for me, Ubuntu 10.04 is my principal work operating system. So, I need a solution for this. Hardware and system information: DELL Precision 670 2 internal SATA Hard drives Audigy 2 ZS audio system Factory OS: Windows XP Professional SP3 NVidia 8400 GTS video card More info: williepabon@WP-WrkStation:~$ uname -a Linux WP-WrkStation 2.6.32-38-generic #83-Ubuntu SMP Wed Jan 4 11:13:04 UTC 2012 i686 GNU/Linux williepabon@WP-WrkStation:~$ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 10.04.4 LTS Release: 10.04 Codename: lucid Speed test with the 3 Gigs of RAM installed: williepabon@WP-WrkStation:~$ sudo hdparm -tT /dev/sdc [sudo] password for williepabon: /dev/sdc: Timing cached reads: 84 MB in 2.00 seconds = 41.96 MB/sec Timing buffered disk reads: 4 MB in 3.81 seconds = 1.05 MB/sec This is a very slow transfer rate from a hard drive. I will really appreciate a solution or a work around for this problem. I know that that there are users that have Ubuntu 10.04 with 3 Gigs or more of RAM and they don't have this problem. Same question asked on Launchpad for reference.

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• How does I/O work for large graph databases?

  - by tjb1982

  I should preface this by saying that I'm mostly a front end web developer, trained as a musician, but over the past few years I've been getting more and more into computer science. So one idea I have as a fun toy project to learn about data structures and C programming was to design and implement my own very simple database that would manage an adjacency list of posts. I don't want SQL (maybe I'll do my own query language? I'm just having fun). It should support ACID. It should be capable of storing 1TB let's say. So with that, I was trying to think of how a database even stores data, without regard to data structures necessarily. I'm working on linux, and I've read that in that world "everything is a file," including hardware (like /dev/*), so I think that that obviously has to apply to a database, too, and it clearly does--whether it's MySQL or PostgreSQL or Neo4j, the database itself is a collection of files you can see in the filesystem. That said, there would come a point in scale where loading the entire database into primary memory just wouldn't work, so it doesn't make sense to design it with that mindset (I assume). However, reading from secondary memory would be much slower and regardless some portion of the database has to be in primary memory in order for you to be able to do anything with it. I read this post: Why use a database instead of just saving your data to disk? And I found it difficult to understand how other databases, like SQLite or Neo4j, read and write from secondary memory and are still very fast (faster, it would seem, than simply writing files to the filesystem as the above question suggests). It seems the key is indexing. But even indexes need to be stored in secondary memory. They are inherently smaller than the database itself, but indexes in a very large database might be prohibitively large, too. So my question is how is I/O generally done with large databases like the one I described above that would be at least 1TB storing a big adjacency list? If indexing is more or less the answer, how exactly does indexing work--what data structures should be involved?

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• Subterranean IL: Volatile

  - by Simon Cooper

  This time, we'll be having a look at the volatile. prefix instruction, and one of the differences between volatile in IL and C#. The volatile. prefix volatile is a tricky one, as there's varying levels of documentation on it. From what I can see, it has two effects: It prevents caching of the load or store value; rather than reading or writing to a cached version of the memory location (say, the processor register or cache), it forces the value to be loaded or stored at the 'actual' memory location, so it is then immediately visible to other threads. It forces a memory barrier at the prefixed instruction. This ensures instructions don't get re-ordered around the volatile instruction. This is slightly more complicated than it first seems, and only seems to matter on certain architectures. For more details, Joe Duffy has a blog post going into the details. For this post, I'll be concentrating on the first aspect of volatile. Caching field accesses To demonstrate this, I created a simple multithreaded IL program. It boils down to the following code: .class public Holder { .field public static class Holder holder .field public bool stop .method public static specialname void .cctor() { newobj instance void Holder::.ctor() stsfld class Holder Holder::holder ret }}.method private static void Main() { .entrypoint // Thread t = new Thread(new ThreadStart(DoWork)) // t.Start() // Thread.Sleep(2000) // Console.WriteLine("Stopping thread...") ldsfld class Holder Holder::holder ldc.i4.1 stfld bool Holder::stop call instance void [mscorlib]System.Threading.Thread::Join() ret}.method private static void DoWork() { ldsfld class Holder Holder::holder // while (!Holder.holder.stop) {} DoWork: dup ldfld bool Holder::stop brfalse DoWork pop ret} If you compile and run this code, you'll find that the call to Thread.Join() never returns - the DoWork spinlock is reading a cached version of Holder.stop, which is never being updated with the new value set by the Main method. Adding volatile to the ldfld fixes this: dupvolatile.ldfld bool Holder::stopbrfalse DoWork The volatile ldfld forces the field access to read direct from heap memory, which is then updated by the main thread, rather than using a cached copy. volatile in C# This highlights one of the differences between IL and C#. In IL, volatile only applies to the prefixed instruction, whereas in C#, volatile is specified on a field to indicate that all accesses to that field should be volatile (interestingly, there's no mention of the 'no caching' aspect of volatile in the C# spec; it only focuses on the memory barrier aspect). Furthermore, this information needs to be stored within the assembly somehow, as such a field might be accessed directly from outside the assembly, but there's no concept of a 'volatile field' in IL! How this information is stored with the field will be the subject of my next post.

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• Map and fill texture using PBO (OpenGL 3.3)

  - by NtscCobalt

  I'm learning OpenGL 3.3 trying to do the following (as it is done in D3D)... Create Texture of Width, Height, Pixel Format Map texture memory Loop write pixels Unmap texture memory Set Texture Render Right now though it renders as if the entire texture is black. I can't find a reliable source for information on how to do this though. Almost every tutorial I've found just uses glTexSubImage2D and passes a pointer to memory. Here is basically what my code does... (In this case it is generating an 1-byte Alpha Only texture but it is rendering it as the red channel for debugging) GLuint pixelBufferID; glGenBuffers(1, &pixelBufferID); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pixelBufferID); glBufferData(GL_PIXEL_UNPACK_BUFFER, 512 * 512 * 1, nullptr, GL_STREAM_DRAW); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0); GLuint textureID; glGenTextures(1, &textureID); glBindTexture(GL_TEXTURE_2D, textureID); glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, 512, 512, 0, GL_RED, GL_UNSIGNED_BYTE, nullptr); glBindTexture(GL_TEXTURE_2D, 0); glBindTexture(GL_TEXTURE_2D, textureID); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, pixelBufferID); void *Memory = glMapBuffer(GL_PIXEL_UNPACK_BUFFER, GL_WRITE_ONLY); // Memory copied here, I know this is valid because it is the same loop as in my working D3D version glUnmapBuffer(GL_PIXEL_UNPACK_BUFFER); glBindBuffer(GL_PIXEL_UNPACK_BUFFER, 0); And then here is the render loop. // This chunk left in for completeness glUseProgram(glProgramId); glBindVertexArray(glVertexArrayId); glBindBuffer(GL_ARRAY_BUFFER, glVertexBufferId); glEnableVertexAttribArray(0); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 20, 0); glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 20, 12); GLuint transformLocationID = glGetUniformLocation(3, 'transform'); glUniformMatrix4fv(transformLocationID , 1, true, somematrix) // Not sure if this is all I need to do glBindTexture(GL_TEXTURE_2D, pTex->glTextureId); GLuint textureLocationID = glGetUniformLocation(glProgramId, "texture"); glUniform1i(textureLocationID, 0); glDrawArrays(GL_TRIANGLES, Offset*3, Triangles*3); Vertex Shader #version 330 core in vec3 Position; in vec2 TexCoords; out vec2 TexOut; uniform mat4 transform; void main() { TexOut = TexCoords; gl_Position = vec4(Position, 1.0) * transform; } Pixel Shader #version 330 core uniform sampler2D texture; in vec2 TexCoords; out vec4 fragColor; void main() { // Output color fragColor.r = texture2D(texture, TexCoords).r; fragColor.g = 0.0f; fragColor.b = 0.0f; fragColor.a = 1.0; }

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• Given a trace of packets, how would you group them into flows?

  - by zxcvbnm

  I've tried it these ways so far: 1) Make a hash with the source IP/port and destination IP/port as keys. Each position in the hash is a list of packets. The hash is then saved in a file, with each flow separated by some special characters/line. Problem: Not enough memory for large traces. 2) Make a hash with the same key as above, but only keep in memory the file handles. Each packet is then put into the hash[key] that points to the right file. Problems: Too many flows/files (~200k) and it might run out of memory as well. 3) Hash the source IP/port and destination IP/port, then put the info inside a file. The difference between 2 and 3 is that here the files are opened and closed for each operation, so I don't have to worry about running out of memory because I opened too many at the same time. Problems: WAY too slow, same number of files as 2 so also impractical. 4) Make a hash of the source IP/port pairs and then iterate over the whole trace for each flow. Take the packets that are part of that flow and place them into the output file. Problem: Suppose I have a 60 MB trace that has 200k flows. This way, I would process, say, a 60 MB file 200k times. Maybe removing the packets as I iterate would make it not so painful, but so far I'm not sure this would be a good solution. 5) Split them by IP source/destination and then create a single file for each one, separating the flows by special characters. Still too many files (+50k). Right now I'm using Ruby to do it, which might've been a bad idea, I guess. Currently I've filtered the traces with tshark so that they only have relevant info, so I can't really make them any smaller. I thought about loading everything in memory as described in 1) using C#/Java/C++, but I was wondering if there wouldn't be a better approach here, especially since I might also run out of memory later on even with a more efficient language if I have to use larger traces. In summary, the problem I'm facing is that I either have too many files or that I run out of memory. I've also tried searching for some tool to filter the info, but I don't think there is one. The ones I've found only return some statistics and wouldn't scan for every flow as I need.

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• Few doubts regarding Bitmaps , Images & `using` blocks

  - by imageWorker

  I caught up in this problem. http://stackoverflow.com/questions/2559826/garbage-collector-not-doing-its-job-memory-consumption-1-5gb-outofmemory-exc I feel that there is something wrong in my understanding. Please clarify these things. Destructor & IDisposable.Dispose are two methods for freeing resources that are not not under the control of .NET. Which means, everything except memory. right? using blocks are just better way of calling IDisposable.Dispose() method of an object. This is the main code I'm referring to. class someclass { static someMethod(Bitmap img) { Bitmap bmp = new Bitmap(img); //statement1 // some code here and return } } here is class I'm using for testing: class someotherClass { public static voide Main() { foreach (string imagePath in imagePathsArray) { using (Bitmap img1 = new Bitmap(imagePath)) { someclass.someMethod(img1); // does some more processing on `img1` } } } } Is there any memory leak with statement1? Question1: If each image size is say 10MB. Then does this bmp object occupy atleast 10MB? What I mean is, will it make completely new copy of entire image? or just refer to it? Question2:should I or should I not put the statement1 in using block? My Argument: We should not. Because using is not for freeing memory but for freeing the resources (file handle in this case). If I use it in using block. It closes file handle here encapsulated by this bmp object. It means we are also closing filehandle for the caller's img1 object. Which is not correct? As of the memory leak. No there is no scope of memory leak here. Because reference bmp is destroyed when this method is returned. Which leaves memory it refered without any pointer. So, its garbage collected. Am I right? Edit: class someclass { static Bitmap someMethod(Bitmap img) { Bitmap bmp = new Bitmap(img); //can I use `using` block on this enclosing `return bmp`; ??? // do some processing on bmp here return bmp; } }

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• lxc containers hangs after upgrade to 13.10

  - by doug123

  I have 3 lxc containers. They were all working fine on 12.10 and I upgraded the containers with do-release-upgrade on the containers to 13.04 and 13.10 and that worked great. Then I upgraded the host to 13.04 and then 13.10 and now the 3 containers hang with this: >lxc-start -n as1 -l DEBUG -o $(tty) lxc-start 1383145786.513 INFO lxc_start_ui - using rcfile /var/lib/lxc/as1/config lxc-start 1383145786.513 WARN lxc_log - lxc_log_init called with log already initialized lxc-start 1383145786.513 INFO lxc_apparmor - aa_enabled set to 1 lxc-start 1383145786.514 DEBUG lxc_conf - allocated pty '/dev/pts/2' (5/6) lxc-start 1383145786.514 DEBUG lxc_conf - allocated pty '/dev/pts/13' (7/8) lxc-start 1383145786.514 DEBUG lxc_conf - allocated pty '/dev/pts/14' (9/10) lxc-start 1383145786.514 DEBUG lxc_conf - allocated pty '/dev/pts/15' (11/12) lxc-start 1383145786.514 DEBUG lxc_conf - allocated pty '/dev/pts/17' (13/14) lxc-start 1383145786.514 DEBUG lxc_conf - allocated pty '/dev/pts/18' (15/16) lxc-start 1383145786.514 DEBUG lxc_conf - allocated pty '/dev/pts/19' (17/18) lxc-start 1383145786.514 DEBUG lxc_conf - allocated pty '/dev/pts/20' (19/20) lxc-start 1383145786.514 INFO lxc_conf - tty's configured lxc-start 1383145786.514 DEBUG lxc_start - sigchild handler set lxc-start 1383145786.514 DEBUG lxc_console - opening /dev/tty for console peer lxc-start 1383145786.514 DEBUG lxc_console - using '/dev/tty' as console lxc-start 1383145786.514 DEBUG lxc_console - 6242 got SIGWINCH fd 25 lxc-start 1383145786.514 DEBUG lxc_console - set winsz dstfd:22 cols:177 rows:53 lxc-start 1383145786.514 INFO lxc_start - 'as1' is initialized lxc-start 1383145786.522 DEBUG lxc_start - Not dropping cap_sys_boot or watching utmp lxc-start 1383145786.524 DEBUG lxc_conf - mac address of host interface 'vethB4L35W' changed to private fe:7c:96:a0:ae:29 lxc-start 1383145786.525 DEBUG lxc_conf - instanciated veth 'vethB4L35W/vethVC61K2', index is '26' lxc-start 1383145786.529 DEBUG lxc_cgroup - cgroup 'memory.limit_in_bytes' set to '20G' lxc-start 1383145786.529 DEBUG lxc_cgroup - cgroup 'cpuset.cpus' set to '12-23' lxc-start 1383145786.529 INFO lxc_cgroup - cgroup has been setup lxc-start 1383145786.555 DEBUG lxc_conf - move 'eth0' to '6249' lxc-start 1383145786.555 INFO lxc_conf - 'as1' hostname has been setup lxc-start 1383145786.575 DEBUG lxc_conf - 'eth0' has been setup lxc-start 1383145786.575 INFO lxc_conf - network has been setup lxc-start 1383145786.575 INFO lxc_conf - looking at .44 42 252:0 / / rw,relatime - ext4 /dev/mapper/limitorderbook1-root rw,errors=remount-ro,data=ordered . lxc-start 1383145786.575 INFO lxc_conf - now p is . /. lxc-start 1383145786.575 INFO lxc_conf - looking at .52 44 0:5 / /dev rw,relatime - devtmpfs udev rw,size=32961632k,nr_inodes=8240408,mode=755 . lxc-start 1383145786.575 INFO lxc_conf - now p is . /dev. lxc-start 1383145786.575 INFO lxc_conf - looking at .61 52 0:11 / /dev/pts rw,nosuid,noexec,relatime - devpts devpts rw,mode=600,ptmxmode=000 . lxc-start 1383145786.575 INFO lxc_conf - now p is . /dev/pts. lxc-start 1383145786.575 INFO lxc_conf - looking at .68 44 0:15 / /run rw,nosuid,noexec,relatime - tmpfs tmpfs rw,size=6594456k,mode=755 . lxc-start 1383145786.575 INFO lxc_conf - now p is . /run. lxc-start 1383145786.575 INFO lxc_conf - looking at .69 68 0:18 / /run/lock rw,nosuid,nodev,noexec,relatime - tmpfs none rw,size=5120k . lxc-start 1383145786.575 INFO lxc_conf - now p is . /run/lock. lxc-start 1383145786.575 INFO lxc_conf - looking at .72 68 0:19 / /run/shm rw,nosuid,nodev,relatime - tmpfs none rw . lxc-start 1383145786.575 INFO lxc_conf - now p is . /run/shm. lxc-start 1383145786.575 INFO lxc_conf - looking at .73 68 0:21 / /run/user rw,nosuid,nodev,noexec,relatime - tmpfs none rw,size=102400k,mode=755 . lxc-start 1383145786.575 INFO lxc_conf - now p is . /run/user. lxc-start 1383145786.575 INFO lxc_conf - looking at .76 44 0:14 / /sys rw,nosuid,nodev,noexec,relatime - sysfs sysfs rw . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys. lxc-start 1383145786.575 INFO lxc_conf - looking at .77 76 0:16 / /sys/fs/cgroup rw,relatime - tmpfs none rw,size=4k,mode=755 . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/cgroup. lxc-start 1383145786.575 INFO lxc_conf - looking at .78 77 0:20 / /sys/fs/cgroup/cpuset rw,relatime - cgroup cgroup rw,cpuset,clone_children . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/cgroup/cpuset. lxc-start 1383145786.575 INFO lxc_conf - looking at .79 77 0:23 / /sys/fs/cgroup/cpu rw,relatime - cgroup cgroup rw,cpu . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/cgroup/cpu. lxc-start 1383145786.575 INFO lxc_conf - looking at .80 77 0:24 / /sys/fs/cgroup/cpuacct rw,relatime - cgroup cgroup rw,cpuacct . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/cgroup/cpuacct. lxc-start 1383145786.575 INFO lxc_conf - looking at .81 77 0:25 / /sys/fs/cgroup/memory rw,relatime - cgroup cgroup rw,memory . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/cgroup/memory. lxc-start 1383145786.575 INFO lxc_conf - looking at .82 77 0:26 / /sys/fs/cgroup/devices rw,relatime - cgroup cgroup rw,devices . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/cgroup/devices. lxc-start 1383145786.575 INFO lxc_conf - looking at .83 77 0:27 / /sys/fs/cgroup/freezer rw,relatime - cgroup cgroup rw,freezer . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/cgroup/freezer. lxc-start 1383145786.575 INFO lxc_conf - looking at .84 77 0:28 / /sys/fs/cgroup/blkio rw,relatime - cgroup cgroup rw,blkio . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/cgroup/blkio. lxc-start 1383145786.575 INFO lxc_conf - looking at .85 77 0:29 / /sys/fs/cgroup/perf_event rw,relatime - cgroup cgroup rw,perf_event . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/cgroup/perf_event. lxc-start 1383145786.575 INFO lxc_conf - looking at .94 77 0:30 / /sys/fs/cgroup/hugetlb rw,relatime - cgroup cgroup rw,hugetlb . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/cgroup/hugetlb. lxc-start 1383145786.575 INFO lxc_conf - looking at .95 77 0:31 / /sys/fs/cgroup/systemd rw,nosuid,nodev,noexec,relatime - cgroup systemd rw,name=systemd . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/cgroup/systemd. lxc-start 1383145786.575 INFO lxc_conf - looking at .96 76 0:17 / /sys/fs/fuse/connections rw,relatime - fusectl none rw . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/fuse/connections. lxc-start 1383145786.575 INFO lxc_conf - looking at .98 76 0:6 / /sys/kernel/debug rw,relatime - debugfs none rw . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/kernel/debug. lxc-start 1383145786.575 INFO lxc_conf - looking at .101 76 0:10 / /sys/kernel/security rw,relatime - securityfs none rw . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/kernel/security. lxc-start 1383145786.575 INFO lxc_conf - looking at .102 76 0:22 / /sys/fs/pstore rw,relatime - pstore none rw . lxc-start 1383145786.575 INFO lxc_conf - now p is . /sys/fs/pstore. lxc-start 1383145786.575 INFO lxc_conf - looking at .103 44 0:3 / /proc rw,nosuid,nodev,noexec,relatime - proc proc rw . lxc-start 1383145786.575 INFO lxc_conf - now p is . /proc. lxc-start 1383145786.575 INFO lxc_conf - looking at .104 44 9:2 / /data rw,relatime - ext4 /dev/md2 rw,errors=remount-ro,data=ordered . lxc-start 1383145786.575 INFO lxc_conf - now p is . /data. lxc-start 1383145786.575 INFO lxc_conf - looking at .105 44 8:1 / /boot rw,relatime - ext2 /dev/sda1 rw,errors=continue . lxc-start 1383145786.575 INFO lxc_conf - now p is . /boot. lxc-start 1383145786.576 DEBUG lxc_conf - mounted '/data/srv/lxc/as1' on '/usr/lib/x86_64-linux-gnu/lxc' lxc-start 1383145786.576 DEBUG lxc_conf - mounted 'none' on '/usr/lib/x86_64-linux-gnu/lxc//dev/pts', type 'devpts' lxc-start 1383145786.576 DEBUG lxc_conf - mounted 'none' on '/usr/lib/x86_64-linux-gnu/lxc//proc', type 'proc' lxc-start 1383145786.576 DEBUG lxc_conf - mounted 'none' on '/usr/lib/x86_64-linux-gnu/lxc//sys', type 'sysfs' lxc-start 1383145786.576 DEBUG lxc_conf - mounted 'none' on '/usr/lib/x86_64-linux-gnu/lxc//run', type 'tmpfs' lxc-start 1383145786.576 INFO lxc_conf - mount points have been setup lxc-start 1383145786.577 INFO lxc_conf - console has been setup lxc-start 1383145786.577 INFO lxc_conf - 8 tty(s) has been setup lxc-start 1383145786.577 INFO lxc_conf - rootfs path is ./data/srv/lxc/as1., mount is ./usr/lib/x86_64-linux-gnu/lxc. lxc-start 1383145786.577 INFO lxc_apparmor - I am 1, /proc/self points to 1 lxc-start 1383145786.577 DEBUG lxc_conf - created '/usr/lib/x86_64-linux-gnu/lxc/lxc_putold' directory lxc-start 1383145786.577 DEBUG lxc_conf - mountpoint for old rootfs is '/usr/lib/x86_64-linux-gnu/lxc/lxc_putold' lxc-start 1383145786.577 DEBUG lxc_conf - pivot_root syscall to '/usr/lib/x86_64-linux-gnu/lxc' successful lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/dev/pts' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/run/lock' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/run/shm' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/run/user' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/cgroup/cpuset' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/cgroup/cpu' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/cgroup/cpuacct' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/cgroup/memory' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/cgroup/devices' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/cgroup/freezer' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/cgroup/blkio' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/cgroup/perf_event' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/cgroup/hugetlb' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/cgroup/systemd' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/fuse/connections' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/kernel/debug' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/kernel/security' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/pstore' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/proc' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/data' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/boot' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/dev' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/run' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys/fs/cgroup' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold/sys' lxc-start 1383145786.577 DEBUG lxc_conf - umounted '/lxc_putold' lxc-start 1383145786.577 INFO lxc_conf - created new pts instance lxc-start 1383145786.578 DEBUG lxc_conf - drop capability 'sys_boot' (22) lxc-start 1383145786.578 DEBUG lxc_conf - capabilities have been setup lxc-start 1383145786.578 NOTICE lxc_conf - 'as1' is setup. lxc-start 1383145786.578 DEBUG lxc_cgroup - cgroup 'memory.limit_in_bytes' set to '20G' lxc-start 1383145786.578 DEBUG lxc_cgroup - cgroup 'cpuset.cpus' set to '12-23' lxc-start 1383145786.578 INFO lxc_cgroup - cgroup has been setup lxc-start 1383145786.578 INFO lxc_apparmor - setting up apparmor lxc-start 1383145786.578 INFO lxc_apparmor - changed apparmor profile to lxc-container-default lxc-start 1383145786.578 NOTICE lxc_start - exec'ing '/sbin/init' lxc-start 1383145786.578 INFO lxc_conf - looking at .15 20 0:14 / /sys rw,nosuid,nodev,noexec,relatime - sysfs sysfs rw . lxc-start 1383145786.578 INFO lxc_conf - now p is . /sys. lxc-start 1383145786.578 INFO lxc_conf - looking at .16 20 0:3 / /proc rw,nosuid,nodev,noexec,relatime - proc proc rw . lxc-start 1383145786.578 INFO lxc_conf - now p is . /proc. lxc-start 1383145786.578 INFO lxc_conf - looking at .17 20 0:5 / /dev rw,relatime - devtmpfs udev rw,size=32961632k,nr_inodes=8240408,mode=755 . lxc-start 1383145786.578 INFO lxc_conf - now p is . /dev. lxc-start 1383145786.578 INFO lxc_conf - looking at .18 17 0:11 / /dev/pts rw,nosuid,noexec,relatime - devpts devpts rw,mode=600,ptmxmode=000 . lxc-start 1383145786.578 INFO lxc_conf - now p is . /dev/pts. lxc-start 1383145786.578 INFO lxc_conf - looking at .19 20 0:15 / /run rw,nosuid,noexec,relatime - tmpfs tmpfs rw,size=6594456k,mode=755 . lxc-start 1383145786.578 INFO lxc_conf - now p is . /run. lxc-start 1383145786.578 INFO lxc_conf - looking at .20 1 252:0 / / rw,relatime - ext4 /dev/mapper/limitorderbook1-root rw,errors=remount-ro,data=ordered . lxc-start 1383145786.578 INFO lxc_conf - now p is . /. lxc-start 1383145786.578 INFO lxc_conf - looking at .22 15 0:16 / /sys/fs/cgroup rw,relatime - tmpfs none rw,size=4k,mode=755 . lxc-start 1383145786.578 INFO lxc_conf - now p is . /sys/fs/cgroup. lxc-start 1383145786.578 INFO lxc_conf - looking at .23 15 0:17 / /sys/fs/fuse/connections rw,relatime - fusectl none rw . lxc-start 1383145786.578 INFO lxc_conf - now p is . /sys/fs/fuse/connections. lxc-start 1383145786.578 INFO lxc_conf - looking at .24 15 0:6 / /sys/kernel/debug rw,relatime - debugfs none rw . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/kernel/debug. lxc-start 1383145786.579 INFO lxc_conf - looking at .25 15 0:10 / /sys/kernel/security rw,relatime - securityfs none rw . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/kernel/security. lxc-start 1383145786.579 INFO lxc_conf - looking at .26 19 0:18 / /run/lock rw,nosuid,nodev,noexec,relatime - tmpfs none rw,size=5120k . lxc-start 1383145786.579 INFO lxc_conf - now p is . /run/lock. lxc-start 1383145786.579 INFO lxc_conf - looking at .27 19 0:19 / /run/shm rw,nosuid,nodev,relatime - tmpfs none rw . lxc-start 1383145786.579 INFO lxc_conf - now p is . /run/shm. lxc-start 1383145786.579 INFO lxc_conf - looking at .28 22 0:20 / /sys/fs/cgroup/cpuset rw,relatime - cgroup cgroup rw,cpuset,clone_children . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/fs/cgroup/cpuset. lxc-start 1383145786.579 INFO lxc_conf - looking at .29 19 0:21 / /run/user rw,nosuid,nodev,noexec,relatime - tmpfs none rw,size=102400k,mode=755 . lxc-start 1383145786.579 INFO lxc_conf - now p is . /run/user. lxc-start 1383145786.579 INFO lxc_conf - looking at .30 15 0:22 / /sys/fs/pstore rw,relatime - pstore none rw . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/fs/pstore. lxc-start 1383145786.579 INFO lxc_conf - looking at .31 22 0:23 / /sys/fs/cgroup/cpu rw,relatime - cgroup cgroup rw,cpu . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/fs/cgroup/cpu. lxc-start 1383145786.579 INFO lxc_conf - looking at .32 22 0:24 / /sys/fs/cgroup/cpuacct rw,relatime - cgroup cgroup rw,cpuacct . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/fs/cgroup/cpuacct. lxc-start 1383145786.579 INFO lxc_conf - looking at .33 22 0:25 / /sys/fs/cgroup/memory rw,relatime - cgroup cgroup rw,memory . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/fs/cgroup/memory. lxc-start 1383145786.579 INFO lxc_conf - looking at .34 22 0:26 / /sys/fs/cgroup/devices rw,relatime - cgroup cgroup rw,devices . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/fs/cgroup/devices. lxc-start 1383145786.579 INFO lxc_conf - looking at .35 22 0:27 / /sys/fs/cgroup/freezer rw,relatime - cgroup cgroup rw,freezer . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/fs/cgroup/freezer. lxc-start 1383145786.579 INFO lxc_conf - looking at .36 22 0:28 / /sys/fs/cgroup/blkio rw,relatime - cgroup cgroup rw,blkio . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/fs/cgroup/blkio. lxc-start 1383145786.579 INFO lxc_conf - looking at .37 22 0:29 / /sys/fs/cgroup/perf_event rw,relatime - cgroup cgroup rw,perf_event . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/fs/cgroup/perf_event. lxc-start 1383145786.579 INFO lxc_conf - looking at .38 22 0:30 / /sys/fs/cgroup/hugetlb rw,relatime - cgroup cgroup rw,hugetlb . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/fs/cgroup/hugetlb. lxc-start 1383145786.579 INFO lxc_conf - looking at .39 20 9:2 / /data rw,relatime - ext4 /dev/md2 rw,errors=remount-ro,data=ordered . lxc-start 1383145786.579 INFO lxc_conf - now p is . /data. lxc-start 1383145786.579 INFO lxc_conf - looking at .40 20 8:1 / /boot rw,relatime - ext2 /dev/sda1 rw,errors=continue . lxc-start 1383145786.579 INFO lxc_conf - now p is . /boot. lxc-start 1383145786.579 INFO lxc_conf - looking at .41 22 0:31 / /sys/fs/cgroup/systemd rw,nosuid,nodev,noexec,relatime - cgroup systemd rw,name=systemd . lxc-start 1383145786.579 INFO lxc_conf - now p is . /sys/fs/cgroup/systemd. lxc-start 1383145786.579 NOTICE lxc_start - '/sbin/init' started with pid '6249' lxc-start 1383145786.579 WARN lxc_start - invalid pid for SIGCHLD <4>init: ureadahead main process (7) terminated with status 5 <4>init: console-font main process (94) terminated with status 1 And it will just sit there like that for hours at least. The container becomes pingable but I can't ssh and if I try lxc-console -n as1 I get a blank screen. If I do lxc-stop -n as1 or ^C in the window where it has hung I get: ^CTERM environment variable not set. <4>init: plymouth-upstart-bridge main process (192) terminated with status 1 <4>init: hwclock-save main process (187) terminated with status 70 * Asking all remaining processes to terminate... ...done. * All processes ended within 1 seconds... ...done. * Deactivating swap... ...fail! mount: cannot mount block device /dev/md2 read-only * Will now restart But after 20 minutes it hasn't restarted. Any ideas why these containers are hanging?

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• CLSF & CLK 2013 Trip Report by Jeff Liu

  - by jamesmorris

  This is a contributed post from Jeff Liu, lead XFS developer for the Oracle mainline Linux kernel team. Recently, I attended both the China Linux Storage and Filesystem workshop (CLSF), and the China Linux Kernel conference (CLK), which were held in Shanghai. Here are the highlights for both events. CLSF - 17th October XFS update (led by Jeff Liu) XFS keeps rapid progress with a lot of changes, especially focused on the infrastructure/performance improvements as well as  new feature development.  This can be reflected with a sample statistics among XFS/Ext4+JBD2/Btrfs via: # git diff --stat --minimal -C -M v3.7..v3.12-rc4 -- fs/xfs|fs/ext4+fs/jbd2|fs/btrfs XFS: 141 files changed, 27598 insertions(+), 19113 deletions(-) Ext4+JBD2: 39 files changed, 10487 insertions(+), 5454 deletions(-) Btrfs: 70 files changed, 19875 insertions(+), 8130 deletions(-) What made up those changes in XFS? Self-describing metadata(CRC32c). This is a new feature and it contributed about 70% code changes, it can be enabled via `mkfs.xfs -m crc=1 /dev/xxx` for v5 superblock. Transaction log space reservation improvements. With this change, we can calculate the log space reservation at mount time rather than runtime to reduce the the CPU overhead. User namespace support. So both XFS and USERNS can be enabled on kernel configuration begin from Linux 3.10. Thanks Dwight Engen's efforts for this thing. Split project/group quota inodes. Originally, project quota can not be enabled with group quota at the same time because they were share the same quota file inode, now it works but only for v5 super block. i.e, CRC enabled. CONFIG_XFS_WARN, an new lightweight runtime debugger which can be deployed in production environment. Readahead log object recovery, this change can speed up the log replay progress significantly. Speculative preallocation inode tracking, clearing and throttling. The main purpose is to deal with inodes with post-EOF space due to speculative preallocation, support improved quota management to free up a significant amount of unwritten space when at or near EDQUOT. It support backgroup scanning which occurs on a longish interval(5 mins by default, tunable), and on-demand scanning/trimming via ioctl(2). Bitter arguments ensued from this session, especially for the comparison between Ext4 and Btrfs in different areas, I have to spent a whole morning of the 1st day answering those questions. We basically agreed on XFS is the best choice in Linux nowadays because: Stable, XFS has a good record in stability in the past 10 years. Fengguang Wu who lead the 0-day kernel test project also said that he has observed less error than other filesystems in the past 1+ years, I own it to the XFS upstream code reviewer, they always performing serious code review as well as testing. Good performance for large/small files, XFS does not works very well for small files has already been an old story for years. Best choice (maybe) for distributed PB filesystems. e.g, Ceph recommends delopy OSD daemon on XFS because Ext4 has limited xattr size. Best choice for large storage (>16TB). Ext4 does not support a single file more than around 15.95TB. Scalability, any objection to XFS is best in this point? :) XFS is better to deal with transaction concurrency than Ext4, why? The maximum size of the log in XFS is 2038MB compare to 128MB in Ext4. Misc. Ext4 is widely used and it has been proved fast/stable in various loads and scenarios, XFS just need more customers, and Btrfs is still on the road to be a manhood. Ceph Introduction (Led by Li Wang) This a hot topic.  Li gave us a nice introduction about the design as well as their current works. Actually, Ceph client has been included in Linux kernel since 2.6.34 and supported by Openstack since Folsom but it seems that it has not yet been widely deployment in production environment. Their major work is focus on the inline data support to separate the metadata and data storage, reduce the file access time, i.e, a file access need communication twice, fetch the metadata from MDS and then get data from OSD, and also, the small file access is limited by the network latency. The solution is, for the small files they would like to store the data at metadata so that when accessing a small file, the metadata server can push both metadata and data to the client at the same time. In this way, they can reduce the overhead of calculating the data offset and save the communication to OSD. For this feature, they have only run some small scale testing but really saw noticeable improvements. Test environment: Intel 2 CPU 12 Core, 64GB RAM, Ubuntu 12.04, Ceph 0.56.6 with 200GB SATA disk, 15 OSD, 1 MDS, 1 MON. The sequence read performance for 1K size files improved about 50%. I have asked Li and Zheng Yan (the core developer of Ceph, who also worked on Btrfs) whether Ceph is really stable and can be deployed at production environment for large scale PB level storage, but they can not give a positive answer, looks Ceph even does not spread over Dreamhost (subject to confirmation). From Li, they only deployed Ceph for a small scale storage(32 nodes) although they'd like to try 6000 nodes in the future. Improve Linux swap for Flash storage (led by Shaohua Li) Because of high density, low power and low price, flash storage (SSD) is a good candidate to partially replace DRAM. A quick answer for this is using SSD as swap. But Linux swap is designed for slow hard disk storage, so there are a lot of challenges to efficiently use SSD for swap. SWAPOUT swap_map scan swap_map is the in-memory data structure to track swap disk usage, but it is a slow linear scan. It will become a bottleneck while finding many adjacent pages in the use of SSD. Shaohua Li have changed it to a cluster(128K) list, resulting in O(1) algorithm. However, this apporoach needs restrictive cluster alignment and only enabled for SSD. IO pattern In most cases, the swap io is in interleaved pattern because of mutiple reclaimers or a free cluster is shared by all reclaimers. Even though block layer can merge interleaved IO to some extent, but we cannot count on it completely. Hence the per-cpu cluster is added base on the previous change, it can help reclaimer do sequential IO and the block layer will be easier to merge IO. TLB flush: If we're reclaiming one active page, we should first move the page from active lru list to inactive lru list, and then reclaim the page from inactive lru to swap it out. During the process, we need to clear PTE twice: first is 'A'(ACCESS) bit, second is 'P'(PRESENT) bit. Processors need to send lots of ipi which make the TLB flush really expensive. Some works have been done to improve this, including rework smp_call_functiom_many() or remove the first TLB flush in x86, but there still have some arguments here and only parts of works have been pushed to mainline. SWAPIN: Page fault does iodepth=1 sync io, but it's a little waste if only issue a page size's IO. The obvious solution is doing swap readahead. But the current in-kernel swap readahead is arbitary(always 8 pages), and it always doesn't perform well for both random and sequential access workload. Shaohua introduced a new flag for madvise(MADV_WILLNEED) to do swap prefetch, so the changes happen in userspace API and leave the in-kernel readahead unchanged(but I think some improvement can also be done here). SWAP discard As we know, discard is important for SSD write throughout, but the current swap discard implementation is synchronous. He changed it to async discard which allow discard and write run in the same time. Meanwhile, the unit of discard is also optimized to cluster. Misc: lock contention For many concurrent swapout and swapin , the lock contention such as anon_vma or swap_lock is high, so he changed the swap_lock to a per-swap lock. But there still have some lock contention in very high speed SSD because of swapcache address_space lock. Zproject (led by Bob Liu) Bob gave us a very nice introduction about the current memory compression status. Now there are 3 projects(zswap/zram/zcache) which all aim at smooth swap IO storm and promote performance, but they all have their own pros and cons. ZSWAP It is implemented based on frontswap API and it uses a dynamic allocater named Zbud to allocate free pages. Zbud means pairs of zpages are "buddied" and it can only store at most two compressed pages in one page frame, so the max compress ratio is 50%. Each page frame is lru-linked and can do shink in memory pressure. If the compressed memory pool reach its limitation, shink or reclaim happens. It decompress the page frame into two new allocated pages and then write them to real swap device, but it can fail when allocating the two pages. ZRAM Acts as a compressed ramdisk and used as swap device, and it use zsmalloc as its allocator which has high density but may have fragmentation issues. Besides, page reclaim is hard since it will need more pages to uncompress and free just one page. ZRAM is preferred by embedded system which may not have any real swap device. Now both ZRAM and ZSWAP are in driver/staging tree, and in the mm community there are some disscussions of merging ZRAM into ZSWAP or viceversa, but no agreement yet. ZCACHE Handles file page compression but it is removed out of staging recently. From industry (led by Tang Jie, LSI) An LSI engineer introduced several new produces to us. The first is raid5/6 cards that it use full stripe writes to improve performance. The 2nd one he introduced is SandForce flash controller, who can understand data file types (data entropy) to reduce write amplification (WA) for nearly all writes. It's called DuraWrite and typical WA is 0.5. What's more, if enable its Dynamic Logical Capacity function module, the controller can do data compression which is transparent to upper layer. LSI testing shows that with this virtual capacity enables 1x TB drive can support up to 2x TB capacity, but the application must monitor free flash space to maintain optimal performance and to guard against free flash space exhaustion. He said the most useful application is for datebase. Another thing I think it's worth to mention is that a NV-DRAM memory in NMR/Raptor which is directly exposed to host system. Applications can directly access the NV-DRAM via a memory address - using standard system call mmap(). He said that it is very useful for database logging now. This kind of NVM produces are beginning to appear in recent years, and it is said that Samsung is building a research center in China for related produces. IMHO, NVM will bring an effect to current os layer especially on file system, e.g. its journaling may need to redesign to fully utilize these nonvolatile memory. OCFS2 (led by Canquan Shen) Without a doubt, HuaWei is the biggest contributor to OCFS2 in the past two years. They have posted 46 upstream patches and 39 patches have been merged. Their current project is based on 32/64 nodes cluster, but they also tried 128 nodes at the experimental stage. The major work they are working is to support ATS (atomic test and set), it can be works with DLM at the same time. Looks this idea is inspired by the vmware VMFS locking, i.e, http://blogs.vmware.com/vsphere/2012/05/vmfs-locking-uncovered.html CLK - 18th October 2013 Improving Linux Development with Better Tools (Andi Kleen) This talk focused on how to find/solve bugs along with the Linux complexity growing. Generally, we can do this with the following kind of tools: Static code checkers tools. e.g, sparse, smatch, coccinelle, clang checker, checkpatch, gcc -W/LTO, stanse. This can help check a lot of things, simple mistakes, complex problems, but the challenges are: some are very slow, false positives, may need a concentrated effort to get false positives down. Especially, no static checker I found can follow indirect calls (“OO in C”, common in kernel): struct foo_ops { int (*do_foo)(struct foo *obj); } foo->do_foo(foo); Dynamic runtime checkers, e.g, thread checkers, kmemcheck, lockdep. Ideally all kernel code would come with a test suite, then someone could run all the dynamic checkers. Fuzzers/test suites. e.g, Trinity is a great tool, it finds many bugs, but needs manual model for each syscall. Modern fuzzers around using automatic feedback, but notfor kernel yet: http://taviso.decsystem.org/making_software_dumber.pdf Debuggers/Tracers to understand code, e.g, ftrace, can dump on events/oops/custom triggers, but still too much overhead in many cases to run always during debug. Tools to read/understand source, e.g, grep/cscope work great for many cases, but do not understand indirect pointers (OO in C model used in kernel), give us all “do_foo” instances: struct foo_ops { int (*do_foo)(struct foo *obj); } = { .do_foo = my_foo }; foo>do_foo(foo); That would be great to have a cscope like tool that understands this based on types/initializers XFS: The High Performance Enterprise File System (Jeff Liu) [slides] I gave a talk for introducing the disk layout, unique features, as well as the recent changes.   The slides include some charts to reflect the performances between XFS/Btrfs/Ext4 for small files. About a dozen users raised their hands when I asking who has experienced with XFS. I remembered that when I asked the same question in LinuxCon/Japan, only 3 people raised their hands, but they are Chris Mason, Ric Wheeler, and another attendee. The attendee questions were mainly focused on stability, and comparison with other file systems. Linux Containers (Feng Gao) The speaker introduced us that the purpose for those kind of namespaces, include mount/UTS/IPC/Network/Pid/User, as well as the system API/ABI. For the userspace tools, He mainly focus on the Libvirt LXC rather than us(LXC). Libvirt LXC is another userspace container management tool, implemented as one type of libvirt driver, it can manage containers, create namespace, create private filesystem layout for container, Create devices for container and setup resources controller via cgroup. In this talk, Feng also mentioned another two possible new namespaces in the future, the 1st is the audit, but not sure if it should be assigned to user namespace or not. Another is about syslog, but the question is do we really need it? In-memory Compression (Bob Liu) Same as CLSF, a nice introduction that I have already mentioned above. Misc There were some other talks related to ACPI based memory hotplug, smart wake-affinity in scheduler etc., but my head is not big enough to record all those things. -- Jeff Liu

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• Why should main() be short?

  - by Stargazer712

  I've been programming for over 9 years, and according to the advice of my first programming teacher, I always keep my main() function extremely short. At first I had no idea why. I just obeyed without understanding, much to the delight of my professors. After gaining experience, I realized that if I designed my code correctly, having a short main() function just sortof happened. Writing modularized code and following the single responsibility principle allowed my code to be designed in "bunches", and main() served as nothing more than a catalyst to get the program running. Fast forward to a few weeks ago, I was looking at Python's souce code, and I found the main() function: /* Minimal main program -- everything is loaded from the library */ ... int main(int argc, char **argv) { ... return Py_Main(argc, argv); } Yay Python. Short main() function == Good code. Programming teachers were right. Wanting to look deeper, I took a look at Py_Main. In its entirety, it is defined as follows: /* Main program */ int Py_Main(int argc, char **argv) { int c; int sts; char *command = NULL; char *filename = NULL; char *module = NULL; FILE *fp = stdin; char *p; int unbuffered = 0; int skipfirstline = 0; int stdin_is_interactive = 0; int help = 0; int version = 0; int saw_unbuffered_flag = 0; PyCompilerFlags cf; cf.cf_flags = 0; orig_argc = argc; /* For Py_GetArgcArgv() */ orig_argv = argv; #ifdef RISCOS Py_RISCOSWimpFlag = 0; #endif PySys_ResetWarnOptions(); while ((c = _PyOS_GetOpt(argc, argv, PROGRAM_OPTS)) != EOF) { if (c == 'c') { /* -c is the last option; following arguments that look like options are left for the command to interpret. */ command = (char *)malloc(strlen(_PyOS_optarg) + 2); if (command == NULL) Py_FatalError( "not enough memory to copy -c argument"); strcpy(command, _PyOS_optarg); strcat(command, "\n"); break; } if (c == 'm') { /* -m is the last option; following arguments that look like options are left for the module to interpret. */ module = (char *)malloc(strlen(_PyOS_optarg) + 2); if (module == NULL) Py_FatalError( "not enough memory to copy -m argument"); strcpy(module, _PyOS_optarg); break; } switch (c) { case 'b': Py_BytesWarningFlag++; break; case 'd': Py_DebugFlag++; break; case '3': Py_Py3kWarningFlag++; if (!Py_DivisionWarningFlag) Py_DivisionWarningFlag = 1; break; case 'Q': if (strcmp(_PyOS_optarg, "old") == 0) { Py_DivisionWarningFlag = 0; break; } if (strcmp(_PyOS_optarg, "warn") == 0) { Py_DivisionWarningFlag = 1; break; } if (strcmp(_PyOS_optarg, "warnall") == 0) { Py_DivisionWarningFlag = 2; break; } if (strcmp(_PyOS_optarg, "new") == 0) { /* This only affects __main__ */ cf.cf_flags |= CO_FUTURE_DIVISION; /* And this tells the eval loop to treat BINARY_DIVIDE as BINARY_TRUE_DIVIDE */ _Py_QnewFlag = 1; break; } fprintf(stderr, "-Q option should be `-Qold', " "`-Qwarn', `-Qwarnall', or `-Qnew' only\n"); return usage(2, argv[0]); /* NOTREACHED */ case 'i': Py_InspectFlag++; Py_InteractiveFlag++; break; /* case 'J': reserved for Jython */ case 'O': Py_OptimizeFlag++; break; case 'B': Py_DontWriteBytecodeFlag++; break; case 's': Py_NoUserSiteDirectory++; break; case 'S': Py_NoSiteFlag++; break; case 'E': Py_IgnoreEnvironmentFlag++; break; case 't': Py_TabcheckFlag++; break; case 'u': unbuffered++; saw_unbuffered_flag = 1; break; case 'v': Py_VerboseFlag++; break; #ifdef RISCOS case 'w': Py_RISCOSWimpFlag = 1; break; #endif case 'x': skipfirstline = 1; break; /* case 'X': reserved for implementation-specific arguments */ case 'U': Py_UnicodeFlag++; break; case 'h': case '?': help++; break; case 'V': version++; break; case 'W': PySys_AddWarnOption(_PyOS_optarg); break; /* This space reserved for other options */ default: return usage(2, argv[0]); /*NOTREACHED*/ } } if (help) return usage(0, argv[0]); if (version) { fprintf(stderr, "Python %s\n", PY_VERSION); return 0; } if (Py_Py3kWarningFlag && !Py_TabcheckFlag) /* -3 implies -t (but not -tt) */ Py_TabcheckFlag = 1; if (!Py_InspectFlag && (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') Py_InspectFlag = 1; if (!saw_unbuffered_flag && (p = Py_GETENV("PYTHONUNBUFFERED")) && *p != '\0') unbuffered = 1; if (!Py_NoUserSiteDirectory && (p = Py_GETENV("PYTHONNOUSERSITE")) && *p != '\0') Py_NoUserSiteDirectory = 1; if ((p = Py_GETENV("PYTHONWARNINGS")) && *p != '\0') { char *buf, *warning; buf = (char *)malloc(strlen(p) + 1); if (buf == NULL) Py_FatalError( "not enough memory to copy PYTHONWARNINGS"); strcpy(buf, p); for (warning = strtok(buf, ","); warning != NULL; warning = strtok(NULL, ",")) PySys_AddWarnOption(warning); free(buf); } if (command == NULL && module == NULL && _PyOS_optind < argc && strcmp(argv[_PyOS_optind], "-") != 0) { #ifdef __VMS filename = decc$translate_vms(argv[_PyOS_optind]); if (filename == (char *)0 || filename == (char *)-1) filename = argv[_PyOS_optind]; #else filename = argv[_PyOS_optind]; #endif } stdin_is_interactive = Py_FdIsInteractive(stdin, (char *)0); if (unbuffered) { #if defined(MS_WINDOWS) || defined(__CYGWIN__) _setmode(fileno(stdin), O_BINARY); _setmode(fileno(stdout), O_BINARY); #endif #ifdef HAVE_SETVBUF setvbuf(stdin, (char *)NULL, _IONBF, BUFSIZ); setvbuf(stdout, (char *)NULL, _IONBF, BUFSIZ); setvbuf(stderr, (char *)NULL, _IONBF, BUFSIZ); #else /* !HAVE_SETVBUF */ setbuf(stdin, (char *)NULL); setbuf(stdout, (char *)NULL); setbuf(stderr, (char *)NULL); #endif /* !HAVE_SETVBUF */ } else if (Py_InteractiveFlag) { #ifdef MS_WINDOWS /* Doesn't have to have line-buffered -- use unbuffered */ /* Any set[v]buf(stdin, ...) screws up Tkinter :-( */ setvbuf(stdout, (char *)NULL, _IONBF, BUFSIZ); #else /* !MS_WINDOWS */ #ifdef HAVE_SETVBUF setvbuf(stdin, (char *)NULL, _IOLBF, BUFSIZ); setvbuf(stdout, (char *)NULL, _IOLBF, BUFSIZ); #endif /* HAVE_SETVBUF */ #endif /* !MS_WINDOWS */ /* Leave stderr alone - it should be unbuffered anyway. */ } #ifdef __VMS else { setvbuf (stdout, (char *)NULL, _IOLBF, BUFSIZ); } #endif /* __VMS */ #ifdef __APPLE__ /* On MacOS X, when the Python interpreter is embedded in an application bundle, it gets executed by a bootstrapping script that does os.execve() with an argv[0] that's different from the actual Python executable. This is needed to keep the Finder happy, or rather, to work around Apple's overly strict requirements of the process name. However, we still need a usable sys.executable, so the actual executable path is passed in an environment variable. See Lib/plat-mac/bundlebuiler.py for details about the bootstrap script. */ if ((p = Py_GETENV("PYTHONEXECUTABLE")) && *p != '\0') Py_SetProgramName(p); else Py_SetProgramName(argv[0]); #else Py_SetProgramName(argv[0]); #endif Py_Initialize(); if (Py_VerboseFlag || (command == NULL && filename == NULL && module == NULL && stdin_is_interactive)) { fprintf(stderr, "Python %s on %s\n", Py_GetVersion(), Py_GetPlatform()); if (!Py_NoSiteFlag) fprintf(stderr, "%s\n", COPYRIGHT); } if (command != NULL) { /* Backup _PyOS_optind and force sys.argv[0] = '-c' */ _PyOS_optind--; argv[_PyOS_optind] = "-c"; } if (module != NULL) { /* Backup _PyOS_optind and force sys.argv[0] = '-c' so that PySys_SetArgv correctly sets sys.path[0] to '' rather than looking for a file called "-m". See tracker issue #8202 for details. */ _PyOS_optind--; argv[_PyOS_optind] = "-c"; } PySys_SetArgv(argc-_PyOS_optind, argv+_PyOS_optind); if ((Py_InspectFlag || (command == NULL && filename == NULL && module == NULL)) && isatty(fileno(stdin))) { PyObject *v; v = PyImport_ImportModule("readline"); if (v == NULL) PyErr_Clear(); else Py_DECREF(v); } if (command) { sts = PyRun_SimpleStringFlags(command, &cf) != 0; free(command); } else if (module) { sts = RunModule(module, 1); free(module); } else { if (filename == NULL && stdin_is_interactive) { Py_InspectFlag = 0; /* do exit on SystemExit */ RunStartupFile(&cf); } /* XXX */ sts = -1; /* keep track of whether we've already run __main__ */ if (filename != NULL) { sts = RunMainFromImporter(filename); } if (sts==-1 && filename!=NULL) { if ((fp = fopen(filename, "r")) == NULL) { fprintf(stderr, "%s: can't open file '%s': [Errno %d] %s\n", argv[0], filename, errno, strerror(errno)); return 2; } else if (skipfirstline) { int ch; /* Push back first newline so line numbers remain the same */ while ((ch = getc(fp)) != EOF) { if (ch == '\n') { (void)ungetc(ch, fp); break; } } } { /* XXX: does this work on Win/Win64? (see posix_fstat) */ struct stat sb; if (fstat(fileno(fp), &sb) == 0 && S_ISDIR(sb.st_mode)) { fprintf(stderr, "%s: '%s' is a directory, cannot continue\n", argv[0], filename); fclose(fp); return 1; } } } if (sts==-1) { /* call pending calls like signal handlers (SIGINT) */ if (Py_MakePendingCalls() == -1) { PyErr_Print(); sts = 1; } else { sts = PyRun_AnyFileExFlags( fp, filename == NULL ? "<stdin>" : filename, filename != NULL, &cf) != 0; } } } /* Check this environment variable at the end, to give programs the * opportunity to set it from Python. */ if (!Py_InspectFlag && (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') { Py_InspectFlag = 1; } if (Py_InspectFlag && stdin_is_interactive && (filename != NULL || command != NULL || module != NULL)) { Py_InspectFlag = 0; /* XXX */ sts = PyRun_AnyFileFlags(stdin, "<stdin>", &cf) != 0; } Py_Finalize(); #ifdef RISCOS if (Py_RISCOSWimpFlag) fprintf(stderr, "\x0cq\x0c"); /* make frontend quit */ #endif #ifdef __INSURE__ /* Insure++ is a memory analysis tool that aids in discovering * memory leaks and other memory problems. On Python exit, the * interned string dictionary is flagged as being in use at exit * (which it is). Under normal circumstances, this is fine because * the memory will be automatically reclaimed by the system. Under * memory debugging, it's a huge source of useless noise, so we * trade off slower shutdown for less distraction in the memory * reports. -baw */ _Py_ReleaseInternedStrings(); #endif /* __INSURE__ */ return sts; } Good God Almighty...it is big enough to sink the Titanic. It seems as though Python did the "Intro to Programming 101" trick and just moved all of main()'s code to a different function called it something very similar to "main". Here's my question: Is this code terribly written, or are there other reasons reasons to have a short main function? As it stands right now, I see absolutely no difference between doing this and just moving the code in Py_Main() back into main(). Am I wrong in thinking this?

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• Why should main() be short?

  - by Stargazer712

  I've been programming for over 9 years, and according to the advice of my first programming teacher, I always keep my main() function extremely short. At first I had no idea why. I just obeyed without understanding, much to the delight of my professors. After gaining experience, I realized that if I designed my code correctly, having a short main() function just sortof happened. Writing modularized code and following the single responsibility principle allowed my code to be designed in "bunches", and main() served as nothing more than a catalyst to get the program running. Fast forward to a few weeks ago, I was looking at Python's souce code, and I found the main() function: /* Minimal main program -- everything is loaded from the library */ ... int main(int argc, char **argv) { ... return Py_Main(argc, argv); } Yay python. Short main() function == Good code. Programming teachers were right. Wanting to look deeper, I took a look at Py_Main. In its entirety, it is defined as follows: /* Main program */ int Py_Main(int argc, char **argv) { int c; int sts; char *command = NULL; char *filename = NULL; char *module = NULL; FILE *fp = stdin; char *p; int unbuffered = 0; int skipfirstline = 0; int stdin_is_interactive = 0; int help = 0; int version = 0; int saw_unbuffered_flag = 0; PyCompilerFlags cf; cf.cf_flags = 0; orig_argc = argc; /* For Py_GetArgcArgv() */ orig_argv = argv; #ifdef RISCOS Py_RISCOSWimpFlag = 0; #endif PySys_ResetWarnOptions(); while ((c = _PyOS_GetOpt(argc, argv, PROGRAM_OPTS)) != EOF) { if (c == 'c') { /* -c is the last option; following arguments that look like options are left for the command to interpret. */ command = (char *)malloc(strlen(_PyOS_optarg) + 2); if (command == NULL) Py_FatalError( "not enough memory to copy -c argument"); strcpy(command, _PyOS_optarg); strcat(command, "\n"); break; } if (c == 'm') { /* -m is the last option; following arguments that look like options are left for the module to interpret. */ module = (char *)malloc(strlen(_PyOS_optarg) + 2); if (module == NULL) Py_FatalError( "not enough memory to copy -m argument"); strcpy(module, _PyOS_optarg); break; } switch (c) { case 'b': Py_BytesWarningFlag++; break; case 'd': Py_DebugFlag++; break; case '3': Py_Py3kWarningFlag++; if (!Py_DivisionWarningFlag) Py_DivisionWarningFlag = 1; break; case 'Q': if (strcmp(_PyOS_optarg, "old") == 0) { Py_DivisionWarningFlag = 0; break; } if (strcmp(_PyOS_optarg, "warn") == 0) { Py_DivisionWarningFlag = 1; break; } if (strcmp(_PyOS_optarg, "warnall") == 0) { Py_DivisionWarningFlag = 2; break; } if (strcmp(_PyOS_optarg, "new") == 0) { /* This only affects __main__ */ cf.cf_flags |= CO_FUTURE_DIVISION; /* And this tells the eval loop to treat BINARY_DIVIDE as BINARY_TRUE_DIVIDE */ _Py_QnewFlag = 1; break; } fprintf(stderr, "-Q option should be `-Qold', " "`-Qwarn', `-Qwarnall', or `-Qnew' only\n"); return usage(2, argv[0]); /* NOTREACHED */ case 'i': Py_InspectFlag++; Py_InteractiveFlag++; break; /* case 'J': reserved for Jython */ case 'O': Py_OptimizeFlag++; break; case 'B': Py_DontWriteBytecodeFlag++; break; case 's': Py_NoUserSiteDirectory++; break; case 'S': Py_NoSiteFlag++; break; case 'E': Py_IgnoreEnvironmentFlag++; break; case 't': Py_TabcheckFlag++; break; case 'u': unbuffered++; saw_unbuffered_flag = 1; break; case 'v': Py_VerboseFlag++; break; #ifdef RISCOS case 'w': Py_RISCOSWimpFlag = 1; break; #endif case 'x': skipfirstline = 1; break; /* case 'X': reserved for implementation-specific arguments */ case 'U': Py_UnicodeFlag++; break; case 'h': case '?': help++; break; case 'V': version++; break; case 'W': PySys_AddWarnOption(_PyOS_optarg); break; /* This space reserved for other options */ default: return usage(2, argv[0]); /*NOTREACHED*/ } } if (help) return usage(0, argv[0]); if (version) { fprintf(stderr, "Python %s\n", PY_VERSION); return 0; } if (Py_Py3kWarningFlag && !Py_TabcheckFlag) /* -3 implies -t (but not -tt) */ Py_TabcheckFlag = 1; if (!Py_InspectFlag && (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') Py_InspectFlag = 1; if (!saw_unbuffered_flag && (p = Py_GETENV("PYTHONUNBUFFERED")) && *p != '\0') unbuffered = 1; if (!Py_NoUserSiteDirectory && (p = Py_GETENV("PYTHONNOUSERSITE")) && *p != '\0') Py_NoUserSiteDirectory = 1; if ((p = Py_GETENV("PYTHONWARNINGS")) && *p != '\0') { char *buf, *warning; buf = (char *)malloc(strlen(p) + 1); if (buf == NULL) Py_FatalError( "not enough memory to copy PYTHONWARNINGS"); strcpy(buf, p); for (warning = strtok(buf, ","); warning != NULL; warning = strtok(NULL, ",")) PySys_AddWarnOption(warning); free(buf); } if (command == NULL && module == NULL && _PyOS_optind < argc && strcmp(argv[_PyOS_optind], "-") != 0) { #ifdef __VMS filename = decc$translate_vms(argv[_PyOS_optind]); if (filename == (char *)0 || filename == (char *)-1) filename = argv[_PyOS_optind]; #else filename = argv[_PyOS_optind]; #endif } stdin_is_interactive = Py_FdIsInteractive(stdin, (char *)0); if (unbuffered) { #if defined(MS_WINDOWS) || defined(__CYGWIN__) _setmode(fileno(stdin), O_BINARY); _setmode(fileno(stdout), O_BINARY); #endif #ifdef HAVE_SETVBUF setvbuf(stdin, (char *)NULL, _IONBF, BUFSIZ); setvbuf(stdout, (char *)NULL, _IONBF, BUFSIZ); setvbuf(stderr, (char *)NULL, _IONBF, BUFSIZ); #else /* !HAVE_SETVBUF */ setbuf(stdin, (char *)NULL); setbuf(stdout, (char *)NULL); setbuf(stderr, (char *)NULL); #endif /* !HAVE_SETVBUF */ } else if (Py_InteractiveFlag) { #ifdef MS_WINDOWS /* Doesn't have to have line-buffered -- use unbuffered */ /* Any set[v]buf(stdin, ...) screws up Tkinter :-( */ setvbuf(stdout, (char *)NULL, _IONBF, BUFSIZ); #else /* !MS_WINDOWS */ #ifdef HAVE_SETVBUF setvbuf(stdin, (char *)NULL, _IOLBF, BUFSIZ); setvbuf(stdout, (char *)NULL, _IOLBF, BUFSIZ); #endif /* HAVE_SETVBUF */ #endif /* !MS_WINDOWS */ /* Leave stderr alone - it should be unbuffered anyway. */ } #ifdef __VMS else { setvbuf (stdout, (char *)NULL, _IOLBF, BUFSIZ); } #endif /* __VMS */ #ifdef __APPLE__ /* On MacOS X, when the Python interpreter is embedded in an application bundle, it gets executed by a bootstrapping script that does os.execve() with an argv[0] that's different from the actual Python executable. This is needed to keep the Finder happy, or rather, to work around Apple's overly strict requirements of the process name. However, we still need a usable sys.executable, so the actual executable path is passed in an environment variable. See Lib/plat-mac/bundlebuiler.py for details about the bootstrap script. */ if ((p = Py_GETENV("PYTHONEXECUTABLE")) && *p != '\0') Py_SetProgramName(p); else Py_SetProgramName(argv[0]); #else Py_SetProgramName(argv[0]); #endif Py_Initialize(); if (Py_VerboseFlag || (command == NULL && filename == NULL && module == NULL && stdin_is_interactive)) { fprintf(stderr, "Python %s on %s\n", Py_GetVersion(), Py_GetPlatform()); if (!Py_NoSiteFlag) fprintf(stderr, "%s\n", COPYRIGHT); } if (command != NULL) { /* Backup _PyOS_optind and force sys.argv[0] = '-c' */ _PyOS_optind--; argv[_PyOS_optind] = "-c"; } if (module != NULL) { /* Backup _PyOS_optind and force sys.argv[0] = '-c' so that PySys_SetArgv correctly sets sys.path[0] to '' rather than looking for a file called "-m". See tracker issue #8202 for details. */ _PyOS_optind--; argv[_PyOS_optind] = "-c"; } PySys_SetArgv(argc-_PyOS_optind, argv+_PyOS_optind); if ((Py_InspectFlag || (command == NULL && filename == NULL && module == NULL)) && isatty(fileno(stdin))) { PyObject *v; v = PyImport_ImportModule("readline"); if (v == NULL) PyErr_Clear(); else Py_DECREF(v); } if (command) { sts = PyRun_SimpleStringFlags(command, &cf) != 0; free(command); } else if (module) { sts = RunModule(module, 1); free(module); } else { if (filename == NULL && stdin_is_interactive) { Py_InspectFlag = 0; /* do exit on SystemExit */ RunStartupFile(&cf); } /* XXX */ sts = -1; /* keep track of whether we've already run __main__ */ if (filename != NULL) { sts = RunMainFromImporter(filename); } if (sts==-1 && filename!=NULL) { if ((fp = fopen(filename, "r")) == NULL) { fprintf(stderr, "%s: can't open file '%s': [Errno %d] %s\n", argv[0], filename, errno, strerror(errno)); return 2; } else if (skipfirstline) { int ch; /* Push back first newline so line numbers remain the same */ while ((ch = getc(fp)) != EOF) { if (ch == '\n') { (void)ungetc(ch, fp); break; } } } { /* XXX: does this work on Win/Win64? (see posix_fstat) */ struct stat sb; if (fstat(fileno(fp), &sb) == 0 && S_ISDIR(sb.st_mode)) { fprintf(stderr, "%s: '%s' is a directory, cannot continue\n", argv[0], filename); fclose(fp); return 1; } } } if (sts==-1) { /* call pending calls like signal handlers (SIGINT) */ if (Py_MakePendingCalls() == -1) { PyErr_Print(); sts = 1; } else { sts = PyRun_AnyFileExFlags( fp, filename == NULL ? "<stdin>" : filename, filename != NULL, &cf) != 0; } } } /* Check this environment variable at the end, to give programs the * opportunity to set it from Python. */ if (!Py_InspectFlag && (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0') { Py_InspectFlag = 1; } if (Py_InspectFlag && stdin_is_interactive && (filename != NULL || command != NULL || module != NULL)) { Py_InspectFlag = 0; /* XXX */ sts = PyRun_AnyFileFlags(stdin, "<stdin>", &cf) != 0; } Py_Finalize(); #ifdef RISCOS if (Py_RISCOSWimpFlag) fprintf(stderr, "\x0cq\x0c"); /* make frontend quit */ #endif #ifdef __INSURE__ /* Insure++ is a memory analysis tool that aids in discovering * memory leaks and other memory problems. On Python exit, the * interned string dictionary is flagged as being in use at exit * (which it is). Under normal circumstances, this is fine because * the memory will be automatically reclaimed by the system. Under * memory debugging, it's a huge source of useless noise, so we * trade off slower shutdown for less distraction in the memory * reports. -baw */ _Py_ReleaseInternedStrings(); #endif /* __INSURE__ */ return sts; } Good God Almighty...it is big enough to sink the Titanic. It seems as though Python did the "Intro to Programming 101" trick and just moved all of main()'s code to a different function called it something very similar to "main". Here's my question: Is this code terribly written, or are there other reasons to have a short main function? As it stands right now, I see absolutely no difference between doing this and just moving the code in Py_Main() back into main(). Am I wrong in thinking this?

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• Fedora error log file

  - by user111196

  I am running a java application using this wrapper service yajsw. The problem it just stopped without any error in its logs file. So I was wondering will there be any system log file which will indicate the cause of it going down? Partial of the log file. Apr 6 00:12:20 localhost kernel: imklog 3.22.1, log source = /proc/kmsg started. Apr 6 00:12:20 localhost rsyslogd: [origin software="rsyslogd" swVersion="3.22.1" x-pid="2234" x-info="http://www.rsyslog.com"] (re)start Apr 6 00:12:20 localhost kernel: Initializing cgroup subsys cpuset Apr 6 00:12:20 localhost kernel: Initializing cgroup subsys cpu Apr 6 00:12:20 localhost kernel: Linux version 2.6.27.41-170.2.117.fc10.x86_64 ([email protected]) (gcc version 4.3.2 20081105 (Red Hat 4.3.2-7) (GCC) ) #1 SMP Thu Dec 10 10:36:29 EST 2009 Apr 6 00:12:20 localhost kernel: Command line: ro root=UUID=722ebf87-437f-4634-9c68-a82d157fa948 rhgb quiet Apr 6 00:12:20 localhost kernel: KERNEL supported cpus: Apr 6 00:12:20 localhost kernel: Intel GenuineIntel Apr 6 00:12:20 localhost kernel: AMD AuthenticAMD Apr 6 00:12:20 localhost kernel: Centaur CentaurHauls Apr 6 00:12:20 localhost kernel: BIOS-provided physical RAM map: Apr 6 00:12:20 localhost kernel: BIOS-e820: 0000000000000000 - 00000000000a0000 (usable) Apr 6 00:12:20 localhost kernel: BIOS-e820: 0000000000100000 - 00000000cfb50000 (usable) Apr 6 00:12:20 localhost kernel: BIOS-e820: 00000000cfb50000 - 00000000cfb66000 (reserved) Apr 6 00:12:20 localhost kernel: BIOS-e820: 00000000cfb66000 - 00000000cfb85c00 (ACPI data) Apr 6 00:12:20 localhost kernel: BIOS-e820: 00000000cfb85c00 - 00000000d0000000 (reserved) Apr 6 00:12:20 localhost kernel: BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved) Apr 6 00:12:20 localhost kernel: BIOS-e820: 00000000fe000000 - 0000000100000000 (reserved) Apr 6 00:12:20 localhost kernel: BIOS-e820: 0000000100000000 - 0000000330000000 (usable) Apr 6 00:12:20 localhost kernel: DMI 2.5 present. Apr 6 00:12:20 localhost kernel: last_pfn = 0x330000 max_arch_pfn = 0x3ffffffff Apr 6 00:12:20 localhost kernel: x86 PAT enabled: cpu 0, old 0x7040600070406, new 0x7010600070106 Apr 6 00:12:20 localhost kernel: last_pfn = 0xcfb50 max_arch_pfn = 0x3ffffffff Apr 6 00:12:20 localhost kernel: init_memory_mapping Apr 6 00:12:20 localhost kernel: last_map_addr: cfb50000 end: cfb50000 Apr 6 00:12:20 localhost kernel: init_memory_mapping Apr 6 00:12:20 localhost kernel: last_map_addr: 330000000 end: 330000000 Apr 6 00:12:20 localhost kernel: RAMDISK: 37bfc000 - 37fef6c8 Apr 6 00:12:20 localhost kernel: ACPI: RSDP 000F21B0, 0024 (r2 DELL ) Apr 6 00:12:20 localhost kernel: ACPI: XSDT 000F224C, 0084 (r1 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: ACPI: FACP CFB83524, 00F4 (r3 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: ACPI: DSDT CFB66000, 4974 (r1 DELL PE_SC3 1 INTL 20050624) Apr 6 00:12:20 localhost kernel: ACPI: FACS CFB85C00, 0040 Apr 6 00:12:20 localhost kernel: ACPI: APIC CFB83078, 00B6 (r1 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: ACPI: SPCR CFB83130, 0050 (r1 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: ACPI: HPET CFB83184, 0038 (r1 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: ACPI: MCFG CFB831C0, 003C (r1 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: ACPI: WD__ CFB83200, 0134 (r1 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: ACPI: SLIC CFB83338, 0176 (r1 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: ACPI: ERST CFB6AAF4, 0210 (r1 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: ACPI: HEST CFB6AD04, 027C (r1 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: ACPI: BERT CFB6A974, 0030 (r1 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: ACPI: EINJ CFB6A9A4, 0150 (r1 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: ACPI: TCPA CFB834BC, 0064 (r1 DELL PE_SC3 1 DELL 1) Apr 6 00:12:20 localhost kernel: No NUMA configuration found Apr 6 00:12:20 localhost kernel: Faking a node at 0000000000000000-0000000330000000 Apr 6 00:12:20 localhost kernel: Bootmem setup node 0 0000000000000000-0000000330000000 Apr 6 00:12:20 localhost kernel: NODE_DATA [0000000000015000 - 0000000000029fff] Apr 6 00:12:20 localhost kernel: bootmap [000000000002a000 - 000000000008ffff] pages 66 Apr 6 00:12:20 localhost kernel: (7 early reservations) ==> bootmem [0000000000 - 0330000000] Apr 6 00:12:20 localhost kernel: #0 [0000000000 - 0000001000] BIOS data page ==> [0000000000 - 0000001000] Apr 6 00:12:20 localhost kernel: #1 [0000006000 - 0000008000] TRAMPOLINE ==> [0000006000 - 0000008000] Apr 6 00:12:20 localhost kernel: #2 [0000200000 - 0000a310cc] TEXT DATA BSS ==> [0000200000 - 0000a310cc] Apr 6 00:12:20 localhost kernel: #3 [0037bfc000 - 0037fef6c8] RAMDISK ==> [0037bfc000 - 0037fef6c8] Apr 6 00:12:20 localhost kernel: #4 [000009f000 - 0000100000] BIOS reserved ==> [000009f000 - 0000100000] Apr 6 00:12:20 localhost kernel: #5 [0000008000 - 000000c000] PGTABLE ==> [0000008000 - 000000c000] Apr 6 00:12:20 localhost kernel: #6 [000000c000 - 0000015000] PGTABLE ==> [000000c000 - 0000015000] Apr 6 00:12:20 localhost kernel: found SMP MP-table at [ffff8800000fe710] 000fe710 Apr 6 00:12:20 localhost kernel: Zone PFN ranges: Apr 6 00:12:20 localhost kernel: DMA 0x00000000 -> 0x00001000 Apr 6 00:12:20 localhost kernel: DMA32 0x00001000 -> 0x00100000 Apr 6 00:12:20 localhost kernel: Normal 0x00100000 -> 0x00330000 Apr 6 00:12:20 localhost kernel: Movable zone start PFN for each node Apr 6 00:12:20 localhost kernel: early_node_map[3] active PFN ranges Apr 6 00:12:20 localhost kernel: 0: 0x00000000 -> 0x000000a0 Apr 6 00:12:20 localhost kernel: 0: 0x00000100 -> 0x000cfb50 Apr 6 00:12:20 localhost kernel: 0: 0x00100000 -> 0x00330000 Apr 6 00:12:20 localhost kernel: ACPI: PM-Timer IO Port: 0x808 Apr 6 00:12:20 localhost kernel: ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] enabled) Apr 6 00:12:20 localhost kernel: ACPI: LAPIC (acpi_id[0x02] lapic_id[0x04] enabled) Apr 6 00:12:20 localhost kernel: ACPI: LAPIC (acpi_id[0x03] lapic_id[0x02] enabled) Apr 6 00:12:20 localhost kernel: ACPI: LAPIC (acpi_id[0x04] lapic_id[0x06] enabled) Apr 6 00:12:20 localhost kernel: ACPI: LAPIC (acpi_id[0x05] lapic_id[0x01] enabled) Apr 6 00:12:20 localhost kernel: ACPI: LAPIC (acpi_id[0x06] lapic_id[0x05] enabled) Apr 6 00:12:20 localhost kernel: ACPI: LAPIC (acpi_id[0x07] lapic_id[0x03] enabled) Apr 6 00:12:20 localhost kernel: ACPI: LAPIC (acpi_id[0x08] lapic_id[0x07] enabled) Apr 6 00:12:20 localhost kernel: ACPI: LAPIC_NMI (acpi_id[0xff] high edge lint[0x1]) Apr 6 00:12:20 localhost kernel: ACPI: IOAPIC (id[0x08] address[0xfec00000] gsi_base[0]) Apr 6 00:12:20 localhost kernel: IOAPIC[0]: apic_id 8, version 0, address 0xfec00000, GSI 0-23 Apr 6 00:12:20 localhost kernel: ACPI: IOAPIC (id[0x09] address[0xfec81000] gsi_base[64]) Apr 6 00:12:20 localhost kernel: IOAPIC[1]: apic_id 9, version 0, address 0xfec81000, GSI 64-87 Apr 6 00:12:20 localhost kernel: ACPI: IOAPIC (id[0x0a] address[0xfec84000] gsi_base[160]) Apr 6 00:12:20 localhost kernel: IOAPIC[2]: apic_id 10, version 0, address 0xfec84000, GSI 160-183 Apr 6 00:12:20 localhost kernel: ACPI: IOAPIC (id[0x0b] address[0xfec84800] gsi_base[224]) Apr 6 00:12:20 localhost kernel: IOAPIC[3]: apic_id 11, version 0, address 0xfec84800, GSI 224-247 Apr 6 00:12:20 localhost kernel: ACPI: INT_SRC_OVR (bus 0 bus_irq 0 global_irq 2 dfl dfl) Apr 6 00:12:20 localhost kernel: ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 high level) Apr 6 00:12:20 localhost kernel: Setting APIC routing to flat Apr 6 00:12:20 localhost kernel: ACPI: HPET id: 0x8086a201 base: 0xfed00000 Apr 6 00:12:20 localhost kernel: Using ACPI (MADT) for SMP configuration information Apr 6 00:12:20 localhost kernel: SMP: Allowing 8 CPUs, 0 hotplug CPUs Apr 6 00:12:20 localhost kernel: PM: Registered nosave memory: 00000000000a0000 - 0000000000100000 Apr 6 00:12:20 localhost kernel: PM: Registered nosave memory: 00000000cfb50000 - 00000000cfb66000 Apr 6 00:12:20 localhost kernel: PM: Registered nosave memory: 00000000cfb66000 - 00000000cfb85000 Apr 6 00:12:20 localhost kernel: PM: Registered nosave memory: 00000000cfb85000 - 00000000cfb86000 Apr 6 00:12:20 localhost kernel: PM: Registered nosave memory: 00000000cfb86000 - 00000000d0000000 Apr 6 00:12:20 localhost kernel: PM: Registered nosave memory: 00000000d0000000 - 00000000e0000000 Apr 6 00:12:20 localhost kernel: PM: Registered nosave memory: 00000000e0000000 - 00000000f0000000 Apr 6 00:12:20 localhost kernel: PM: Registered nosave memory: 00000000f0000000 - 00000000fe000000 Apr 6 00:12:20 localhost kernel: PM: Registered nosave memory: 00000000fe000000 - 0000000100000000 Apr 6 00:12:20 localhost kernel: Allocating PCI resources starting at d1000000 (gap: d0000000:10000000) Apr 6 00:12:20 localhost kernel: PERCPU: Allocating 65184 bytes of per cpu data Apr 6 00:12:20 localhost kernel: Built 1 zonelists in Zone order, mobility grouping on. Total pages: 3096524 Apr 6 00:12:20 localhost kernel: Policy zone: Normal Apr 6 00:12:20 localhost kernel: Kernel command line: ro root=UUID=722ebf87-437f-4634-9c68-a82d157fa948 rhgb quiet Apr 6 00:12:20 localhost kernel: Initializing CPU#0 Apr 6 00:12:20 localhost kernel: PID hash table entries: 4096 (order: 12, 32768 bytes) Apr 6 00:12:20 localhost kernel: Extended CMOS year: 2000 Apr 6 00:12:20 localhost kernel: TSC: PIT calibration confirmed by PMTIMER. Apr 6 00:12:20 localhost kernel: TSC: using PMTIMER calibration value Apr 6 00:12:20 localhost kernel: Detected 1994.992 MHz processor. Apr 6 00:12:20 localhost kernel: Console: colour VGA+ 80x25 Apr 6 00:12:20 localhost kernel: console [tty0] enabled Apr 6 00:12:20 localhost kernel: Checking aperture... Apr 6 00:12:20 localhost kernel: No AGP bridge found Apr 6 00:12:20 localhost kernel: PCI-DMA: Using software bounce buffering for IO (SWIOTLB) Apr 6 00:12:20 localhost kernel: Placing software IO TLB between 0x20000000 - 0x24000000 Apr 6 00:12:20 localhost kernel: Memory: 12324244k/13369344k available (3311k kernel code, 253484k reserved, 1844k data, 1296k init) Apr 6 00:12:20 localhost kernel: SLUB: Genslabs=13, HWalign=64, Order=0-3, MinObjects=0, CPUs=8, Nodes=1 Apr 6 00:12:20 localhost kernel: Calibrating delay loop (skipped), value calculated using timer frequency.. 3989.98 BogoMIPS (lpj=1994992) Apr 6 00:12:20 localhost kernel: Security Framework initialized Apr 6 00:12:20 localhost kernel: SELinux: Initializing. Apr 6 00:12:20 localhost kernel: Dentry cache hash table entries: 2097152 (order: 12, 16777216 bytes) Apr 6 00:12:20 localhost kernel: Inode-cache hash table entries: 1048576 (order: 11, 8388608 bytes) Apr 6 00:12:20 localhost kernel: Mount-cache hash table entries: 256 Apr 6 00:12:20 localhost kernel: Initializing cgroup subsys ns Apr 6 00:12:20 localhost kernel: Initializing cgroup subsys cpuacct Apr 6 00:12:20 localhost kernel: Initializing cgroup subsys devices Apr 6 00:12:20 localhost kernel: CPU: L1 I cache: 32K, L1 D cache: 32K Apr 6 00:12:20 localhost kernel: CPU: L2 cache: 4096K Apr 6 00:12:20 localhost kernel: CPU 0/0 -> Node 0 Apr 6 00:12:20 localhost kernel: CPU: Physical Processor ID: 0 Apr 6 00:12:20 localhost kernel: CPU: Processor Core ID: 0 Apr 6 00:12:20 localhost kernel: CPU0: Thermal monitoring enabled (TM1) Apr 6 00:12:20 localhost kernel: using mwait in idle threads. Apr 6 00:12:20 localhost kernel: ACPI: Core revision 20080609 Apr 6 00:12:20 localhost kernel: ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1 Apr 6 00:12:20 localhost kernel: CPU0: Intel(R) Xeon(R) CPU E5335 @ 2.00GHz stepping 07 Apr 6 00:12:20 localhost kernel: Using local APIC timer interrupts. Apr 6 00:12:20 localhost kernel: Detected 20.781 MHz APIC timer. Apr 6 00:12:20 localhost kernel: Booting processor 1/4 ip 6000 Apr 6 00:12:20 localhost kernel: Initializing CPU#1 Apr 6 00:12:20 localhost kernel: Calibrating delay using timer specific routine.. 3990.05 BogoMIPS (lpj=1995026) Apr 6 00:12:20 localhost kernel: CPU: L1 I cache: 32K, L1 D cache: 32K Apr 6 00:12:20 localhost kernel: CPU: L2 cache: 4096K Apr 6 00:12:20 localhost kernel: CPU 1/4 -> Node 0 Apr 6 00:12:20 localhost kernel: CPU: Physical Processor ID: 1 Apr 6 00:12:20 localhost kernel: CPU: Processor Core ID: 0 Apr 6 00:12:20 localhost kernel: CPU1: Thermal monitoring enabled (TM2) Apr 6 00:12:20 localhost kernel: x86 PAT enabled: cpu 1, old 0x7040600070406, new 0x7010600070106 Apr 6 00:12:20 localhost kernel: CPU1: Intel(R) Xeon(R) CPU E5335 @ 2.00GHz stepping 07 Apr 6 00:12:20 localhost kernel: checking TSC synchronization [CPU#0 -> CPU#1]: passed. Apr 6 00:12:20 localhost kernel: Booting processor 2/2 ip 6000 Apr 6 00:12:20 localhost kernel: Initializing CPU#2 Apr 6 00:12:20 localhost kernel: Calibrating delay using timer specific routine.. 3990.05 BogoMIPS (lpj=1995029)

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• Network shares do not mount.

  - by Alex

  My network shares were mounting fine yesterday.. suddenly they are not. They were mounting fine for the last two weeks or however long since I added them. When I run sudo mount -a I get the following error: topsy@monolyth:~$ sudo mount -a mount error(12): Cannot allocate memory Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) mount error(12): Cannot allocate memory Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) mount error(12): Cannot allocate memory Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) mount error(12): Cannot allocate memory Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) topsy@monolyth:~$ I followed this guide when setting them up: http://ubuntuforums.org/showthread.php?t=288534 So I tried removing them by doing the reverse, and then rebooting, then adding them again and rebooting. Problem persists.

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• SD cards and CPRM protection

  - by Francesco Turco

  Before buying an SD memory card, I'd like to know something more about the CPRM protection, in particular: Does CPRM influence the way I am supposed to access my own data? That is, does CPRM encrypt it? Could CPRM prevent me from accessing my own data? Is it possible to disable or eliminate CPRM from either the memory card or the card reader? Are there manufacturers selling CPRM-free SD memory cards? Is there any real alternative to CPRM-protected SD memory cards beside USB flash drives? Is Linux support for SD cards good? Thanks.

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• JAVASCRIPT ENABLED

  - by kirchoffs415

  HI, I hope somebody can help, i keep getting the following message when i log on-- Your Javascript is disabled. Limited functionality is available. it will stay for maybe a day sometimes two.I have uninstalled javascript and reinstalled but still the same. Iam using chrome. any help would be gratefull many thanks Dominic p.s. my system spec is as follows System InformationOS Name Microsoft® Windows Vista™ Home Premium Version 6.0.6002 Service Pack 2 Build 6002 Other OS Description Not Available OS Manufacturer Microsoft Corporation System Name DOM-PC System Manufacturer Dell Inc. System Model Inspiron 1545 System Type X86-based PC Processor Pentium(R) Dual-Core CPU T4200 @ 2.00GHz, 2000 Mhz, 2 Core(s), 2 Logical Processor(s) BIOS Version/Date Dell Inc. A05, 25/02/2009 SMBIOS Version 2.4 Windows Directory C:\Windows System Directory C:\Windows\system32 Boot Device \Device\HarddiskVolume3 Locale United Kingdom Hardware Abstraction Layer Version = "6.0.6002.18005" User Name DOM-PC\DOM Time Zone GMT Standard Time Installed Physical Memory (RAM) 3.00 GB Total Physical Memory 2.96 GB Available Physical Memory 1.38 GB Total Virtual Memory 5.89 GB Available Virtual Memory 4.25 GB Page File Space 3.00 GB Page File C:\pagefile.sys My System Specs

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• Low framerate on background apps

  - by user1698923

  My problem is that when a game is running in the foreground, in Full Screen mode, any applications on my second monitor (such as youtube videos, videos, not app specific) drop their frame-rate to about 2-3 FPS. It seems like some sort of power management option that I can't track down. As far as I can tell, it's not due to the GPU not being able to keep up. For instance, my PC can play League of Legends at about 280FPS when the framerate is uncapped. If i cap it at 60FPS using the in-game option, it has no affect on the performance of the background app. Summary Operating System Windows 8 Pro 64-bit CPU Intel Core i7 3820 @ 3.60GHz 42 °C Sandy Bridge-E 32nm Technology RAM 12.0GB Triple-Channel DDR3 @ 533MHz (7-7-7-20) Motherboard Gigabyte Technology Co., Ltd. X79-UD3 (SOCKET 0) 37 °C Graphics DELL U2713HM (2560x1440@59Hz) DELL U2713HM (2560x1440@59Hz) 1280MB NVIDIA GeForce GTX 570 (Gigabyte) 58 °C Hard Drives 212GB Volume0 (RAID) 1863GB Western Digital WDC WD20EARS-00MVWB0 (SATA) 36 °C 1863GB Western Digital WDC WD20EARS-00MVWB0 (SATA) 34 °C Optical Drives No optical disk drives detected Audio ASUS Xonar Essence STX Audio Device Operating System Windows 8 Pro 64-bit Computer type: Desktop Graphics Monitor 1 Name DELL U2713HM on NVIDIA GeForce GTX 570 Current Resolution 2560x1440 pixels Work Resolution 2560x1400 pixels State Enabled, Output devices support Multiple displays Extended, Secondary, Enabled Monitor Width 2560 Monitor Height 1440 Monitor BPP 32 bits per pixel Monitor Frequency 59 Hz Device \\.\DISPLAY4\Monitor0 Monitor 2 Name DELL U2713HM on NVIDIA GeForce GTX 570 Current Resolution 2560x1440 pixels Work Resolution 2560x1400 pixels State Enabled, Output devices support Multiple displays Extended, Primary, Enabled Monitor Width 2560 Monitor Height 1440 Monitor BPP 32 bits per pixel Monitor Frequency 59 Hz Device \\.\DISPLAY5\Monitor0 NVIDIA GeForce GTX 570 Manufacturer NVIDIA Model GeForce GTX 570 GPU GF110 Device ID 10DE-1086 Revision A2 Subvendor Gigabyte (1458) Series GeForce GTX 500 Current Performance Level Level 3 Current GPU Clock 845 MHz Current Memory Clock 1900 MHz Current Shader Clock 1690 MHz Voltage 0.988 V Technology 40 nm Die Size 520 mm² Release Date Dec 07, 2010 DirectX Support 11.0 OpenGL Support 5.0 Bus Interface PCI Express x16 Temperature 57 °C Driver version 9.18.13.2018 BIOS Version 70.10.55.00.01 ROPs 40 Shaders 512 unified Memory Type GDDR5 Memory 1280 MB Bus Width 64x5 (320 bit) Filtering Modes 16x Anisotropic Noise Level Moderate Max Power Draw 219 Watts Count of performance levels : 3 Level 1 - "Default" GPU Clock 50 MHz Memory Clock 135 MHz Shader Clock 101 MHz Level 2 - "2D Desktop" GPU Clock 405 MHz Memory Clock 324 MHz Shader Clock 810 MHz Level 3 - "3D Applications" GPU Clock 845 MHz Memory Clock 1900 MHz Shader Clock 1690 MHz Things I've tried: 1) Updating the graphics driver 2) Setting windows power mode to High Performance 3) Reset Nvidia Global Performance settings to default

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• What is a normal value for pages/sec on a Windows Server 2003 Web Server?

  - by Emil Lerch

  I know the answer to this is "it depends", and I know that the counter can and will be thrown off by backup jobs or other things that might use memory mapped files. I'd like to get a bit of clarity over exactly what "it depends" on and some general guidelines around what a healthy web server normally shows for this counter. So if activities regarding memory-mapped files are excluded, if I have ample amounts of memory, should I really see this down close to 0? When should I get suspicious that I might need additional RAM and/or start looking for application memory leaks?

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• What happens when more RAM is installed than the motherboard supports?

  - by DanDan

  I have a free RAM slot and some spare memory that will fit my computer. However the problem is my motherboard only supports 2GB and I have 2GB installed. What would happen if I plugged the spare memory in the RAM slot? The following things spring to mind: Nothing will happen It will work, computer becomes faster Computer becomes slower Explosion Undetermined (Any of the above) Does anyone have any experience of this? Update: Egged on by you zealous lot, I went ahead and stuck the extra memory in. It booted up! Unfortunately, the hunch of some has been proved correct. The memory is reported at the capped limit, rather then the actual available. A shame then! But thank you all for your suggestions, speculations and stories. For your reference, I am using a Dell Insprion 6000 with 2gb installed, latest drivers. I attempted to add 512mb, with no success.

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• Linux: Dropbox alternative with sftp/rsync/... access

  - by Daniel

  Currently on my VPS I'm running couple of sites and Dropbox daemon to store backups. Problem is that VPS has 512M RAM and it was enough until new version of Wordpress (I don't know why, but now it consumes more memory) so I have a really bad choice: either stop Dropbox daemon and backups or to buy more memory (not that expensive but still). So I'm looking for some way to rsync data into Dropbox or similar service or figure out how to make Dropbox consume less memory. Any ideas?

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• How to update grub with puppet?

  - by Tombart

  I would like to change a line in /etc/default/grub with puppet to this: GRUB_CMDLINE_LINUX="cgroup_enable=memory" I've tried to used augeas which seems to do this magic: exec { "update_grub": command => "update-grub", refreshonly => true, } augeas { "grub-serial": context => "/files/etc/default/grub", changes => [ "set /files/etc/default/grub/GRUB_CMDLINE_LINUX[last()] cgroup_enable=memory", ], notify => Exec['update_grub'], } It seems to work, but the result string is not in quotes and also I want to make sure that any other values will be separated by space. GRUB_CMDLINE_LINUX=cgroup_enable=memory Is there some mechanism how to append values and escape the whole thing? GRUB_CMDLINE_LINUX="quiet splash cgroup_enable=memory"

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• Tuning Windows 7 for use in a VM

  - by intuited

  I'm running Windows 7 in a VirtualBox Virtual Machine, and would like to make it run in a more streamlined fashion. I'll be using the install primarily for testing web apps, and have no need for it to run quickly. I would like it to run with minimal memory requirements, and with minimal changes to its virtual hard drive's contents. Changes to the hard drive contents, for example the paging file, result in larger snapshot sizes. Another recent post of mine seems to be related to this issue, but does not directly address issues with Windows. One concern that I have is that Windows seems to be using 17% of its paging file even with over 900MB of memory marked "Standby" or "Free". My uneducated guess is that this is being used to store indexes or some other data that helps to speed up the system but is not really necessary. I'm also wondering if it's normal for Windows to use over 500 MB of "In Use" memory with no apps running. Will this amount decrease if I reduce the amount of "installed" memory in the VM? What steps can I take to reduce the system's memory footprint without incurring an increase in paging file usage?

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• Understanding GPU clock rates

  - by trizicus

  I know how to overclock my CPU (mess with multiplier, and bus speed)... However, I've noticed that it seems a bit more complicated with GPU's. How and where do I start? I've noticed that I can adjust the GPU clock speed in my BIOS. Card I'm overclocking: http://www.nvidia.com/object/product_geforce_gt_240_us.html I found that memory bus speed is (Mem Speed * Bus width) / 8. So obviously a good way to overclock the memory bandwidth is to adjust the memory speed. Now, GPU speed is 550 Mhz. How do I find its speed as well? Do I multiply it by the bus width (128)? What is ideal GPU speed relative to memory bandwidth?

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• VMWare player - how do I start VM on machine with lower RAM? [closed]

  - by katit

  I moved image from one machine to another. Problem is - I didn't shut down' instance, just suspended it. On machine #1 I have 32G and instance had 16Gb allocated. On machine #2 I have only 10G and instance won't resume (due to memory) But I can't lower amount of memory - I guess because machine in "suspended". Anyway to lower memory or "shut down" instance without powering? How do I start it on machine #2?

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• Slow performance on VMWare Linux server after Tomcat install

  - by Loftx

  We have a VMWare ESXi 4.1 server hosting a number of Linux and Windows guests. Recently a new Linux guest was added to this server and seemed to be performing well. Tomcat and some other applications on this server were then installed which seem to have caused the server to run really slowly without any obvious resource issues. Slow performance include: The time taken to bring up the password prompt over ssh takes a few seconds when it was previously instantaneous. The time taken to unzip a zip file which was previously a few seconds now takes around 30 seconds The time taken to compile vmware tools has increased by similar factors Both the VMWare console and monitoring commands don't report any issues with high CPU or memory usage but something is obviously slowing the server down somehow. Does anyone have any ideas what may be causing this issue and how it can be resolved? Thanks, Tom Edit As per your questions I’ve looked at some of the performance indicators on both the VM host and VM guest indicated. Firstly I tried reserving the full amount of memory (3gb) for this VM – no other machines on this server have any memory reservation. The swap in rate and swap out rate for the VM host and guest are now both zero. Balloon memory on the guest is zero and on the host is 3.5gb (total memory on the host is 12gb) The swap rate for the guest is also zero. Swap used by the host is 200mb on average. Compression and decompression rates for the host and guest are zero. Command aborts for the host are zero. Read latency is very low – maximum 10ms average 0.8ms. Write latency is higher – a few spikes to 170ms but mostly around 25ms – is this bad? Queue command latency is zero . Physical disk read latency averages 5ms but often 10ms Physical disk write latency averages 15ms but is often 20ms I hope this helps - let me know if you need any more information.

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• How seriously should I take ECC correctable error warnings?

  - by David Mackintosh

  I have a pile of Sun X2200-M2 servers. These servers have ECC memory. In some of these servers, I am getting warnings in the eLOM about "correctable ECC errors detected", eg: # ssh regress11 ipmitool sel elist 1 | 05/20/2010 | 14:20:27 | Memory CPU0 DIMM2 | Correctable ECC | Asserted 2 | 05/20/2010 | 14:33:47 | Memory CPU0 DIMM2 | Correctable ECC | Asserted ...some more frequently than others. The kernel on this particular system is throwing EDAC errors as well, although with far more frequency than the eLOM is recording ECC events: EDAC k8 MC0: general bus error: participating processor(local node response), time-out(no timeout) memory transaction type(generic read), mem or i/o(mem access), cache level(generic) MC0: CE page 0x42a194, offset 0x60, grain 8, syndrome 0xf654, row 4, channel 1, label "": k8_edac MC0: CE - no information available: k8_edac Error Overflow set EDAC k8 MC0: extended error code: ECC chipkill x4 error EDAC k8 MC0: general bus error: participating processor(local node response), time-out(no timeout) memory transaction type(generic read), mem or i/o(mem access), cache level(generic) MC0: CE page 0x48cb94, offset 0x10, grain 8, syndrome 0xf654, row 5, channel 1, label "": k8_edac MC0: CE - no information available: k8_edac Error Overflow set EDAC k8 MC0: extended error code: ECC chipkill x4 error Now if the server is detecting Uncorrectable ECC, the system resets, so clearly that's bad and removing/replacing the identified stick or pair corrects the issue. But I am thinking that if the error is Correctable, then there's no immediate issue -- I can treat this as a warning and be prepared to pull the stick/pair if an uncorrectable error starts occurring?

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