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  • HDDs randomly falling off raid

    - by michael
    I really need help on this it's Saturday long weekend.No customer service help:( .I recently build new server/light duty desktop.Main purpose is only file sharing.Raid configuration :Adaptec 6805 ,8x 3TB HDD WD Red,Intel RES2SV240 expander,Raid 6,set in Intel mobo DZ 77GA-70K.I upgraded firmwares, but I'm having strange problem. During Build Verify segment 7 got missing.I just reinsert drive into hot swap bay and it started to rebuild Array.After rebuild was done another segments 0 and 5 gone missing while build/verify.I reinserted drives and now I'm praying that raid is going to rebuild successfully from remaining 6 drives,because i already transfer some data on it(I know it was bad idea).I checked S.M.A.R.T on missing drives , it only says link failure and aborted commands on one of them.No Errors on HDDs.Connections and cables are good.I added 2 fans blowing on RAID controller because it was getting too hot, so I guess overheating shouldn't be issue.What can be possibly wrong? Thank you for help.

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  • Solr performance (tomcat) - High load

    - by Ward Loockx
    I'm relatively new to solr. I have a production site running on a VPS, but now I'm having serious load issues. I don't know where to start in order to get the load down... VPS specs (linode.com 512) 512 MB RAM 4 CPU (1x priority) Looks like my solr server (tomcat) is using a lot of CPU power You can find my solrconfig.xml on http://pastebin.com/qdfi8Med and my schema.xml on http://pastebin.com/rRusDP8b I've tried to increaese the cache size, but this didn't do anything on the load. You can see the stats page below. EDIT - Because the screenshot was unclear, I took smaller screenshots if what (I think) is important. Dismax query handler stats Caches stats Thanks for the help!

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  • Why are browsers so heavy?

    - by Kaivosukeltaja
    Back in 1998 I had a computer with 233MHz Pentium MMX CPU and a GFX card with no 3D acceleration. It was able to run games like Quake II at a decent FPS rate. My current computer has tons more performance and a mid-class GPU, yet struggles to reach 20 FPS when rendering a single model inside a skybox with WebGL. Even regular pages with lots of 2D CSS animations bring many modern computers to their metaphorical knees. As a web developer I understand there's a lot going on in a web page but not what makes it that heavy. Modern browsers compile JavaScript to CPU native machine code before running it and rendering into a canvas element shouldn't trigger DOM rebuilds so theoretically it should be a lot faster than it is. What am I missing here and is it possible to avoid or minimize whatever is making the browsers slow to build more efficient websites?

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  • What is this PHP process? It is crippling my server

    - by user1019588
    This process has been using 65% of my site CPU and has lasted for about 10 minutes now (aren't processes only supposed to go for a couple seconds?) It is obviously something with mysql. This makes sense because I have a lot of queries going, but something still seems a bit odd... This could have something to do with my bad PDO connection that I mentioned in the previous question. Perhaps I am opening too many connections or something like that? Here is the stats on it: Owner: mysql Priority: 0 CPU %: 61.1 Memory %: 0.4 Command:/usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin-dir=/usr/lib64/mysql/plugin --user=mysql --log-error=/var/lib/mysql/cvps54834319.myhost.com.err --pid-file=/var/lib/mysql/cvps54834319.myhost.com.pid Thanks for any help on this. I have over 10GHZ on my server so this is very concerning to me.

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  • Computer loads BIOS, but won't load OS

    - by LEGEND383
    I have just purchased a brand new motherboard bundle, installed into the old case with the old PSU and the old HDD. I can get into the BIOS, but whenever I try to boot from the HDD, it just sits with the fans going, but nothing is displayed. The moniter works (tested with another machine), and I'd hope there are no problems with the motherboard, CPU or RAM because as I said I only brought them today. The only things I can think of are: The PSU's motherboard connector is a 20-pin, and the motherboard has a 24-pin connector (not a problem with the previous board) The OS is not supported (doesn't seem likly to me, but possible I guess) Here is my system configuration: Motherboard: ASUS F1A55-M le CPU: AMD APU A6 3500 HDD: 1Tb SATA RAM: 4Gb DDR3 OS: Ubuntu Satanic v666.9 PSU: Winpower ATX-400 (this thing is REALLY old) If anyone is able to offer a reason as to why this is not working, or a possible solution, it would be greatly appriciated.

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  • Windows 7 immediately disconnects a USB drive

    - by Daniel Saner
    I am having a problem with Windows 7 x64 consistently disconnecting one specific USB mass storage drive immediately after it is connected. The drive in question is a Cowon C2 digital music player which works in standard mass storage controller mode (i.e. no device-specific drivers needed/available). When I connect the player, Windows plays the "USB connect" sound and the device appears (under its correct name) in the device manager, but it never appears as a drive. The player itself displays "USB Connected" for a split-second before reporting that it has been disconnected again. Since the player, by design, reboots after it has been disconnected, Windows plays the "USB disconnect" sound before restarting the whole cycle once the player has powered back on. I am connecting the player through an Intel X79 Chipset motherboard (Gigabyte GA-X79-UD3) to Windows 7 Pro 64-bit. The player used to work fine the first few times I connected it, showing up as an external drive; it only recently stopped working. It is not a problem with the player, since it works fine when connected to another computer, even such running the exact same operating system. It is also not a problem with the USB controller, since the issue is the same on both the Intel USB 2.0 and the Fresco Logic FL1009 USB 3.0 controller ports. I have also not had the problem with any other drive so far. Among the things I have tried so far: Disabling USB legacy mode in BIOS Disabling energy-saving power down for all USB controllers in Windows' device manager Removing and reinstalling Windows' USB mass storage driver Removing and reinstalling Intel and Fresco Logic USB controller driver Restoring the player to factory defaults None of these made a difference. Again, the player used to work fine on the exact same system just days ago; I didn't install any new hardware or drivers on it since then. I would be very grateful for any hints on what else to try. Edit: Here is another new hint; I found out that when I connect the drive before booting Windows, it is available in Windows Explorer as it should, and does not automatically disconnect. If I remove and reconnect it though, the infinite connect/disconnect-loop starts anew.

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  • Visual Studio 2012 intermittent lockup

    - by user1892678
    Visual Studio 2012 intermittently locks up on me. I notice that devenv.exe jumps to 50% CPU utilization. The CPU stays at this level for a few minutes and then drops. While its at 50% utilization I can still use the IDE. However, intermittently it stops responding (as though it was performing some sort of background process). It only lasts for a few seconds. Also this happens when debugging. I'm running under Windows 7 and I'm using Telerik controls. I've disabled add-ins and extensions and have had no success. Any ideas would be appreciated? Thanks

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  • what may cause unexpected log outs?

    - by lalebarde
    Sometimes, my Linux PC unexpectedly closes my session (log out) while I am working, and puts me back the login window. If I have terminal 1 logged with root and 2 logged with another user (without X), these ones are not logged out. For example, for the last three hours, it has happened five times. Other times, it leads to a reboot. So I have investigated: the UPS, but the behaviour is unchanged without it). the temperatures, but everything is fine (cpu, disks, video card). I have started to investigate also: the memory (partially tested - I have to run a full testyt next night). EDIT: totally tested and passed. My configuration is: Linux 2.6.37-tuxonice x86_64 Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz. Any idea please?

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  • ATI HD 5970 display

    - by user55406
    Hello everyone i'm a little worry about my graphic card. before I get into that I will tell you my system specs. I have intel dx58so mainboard, 6gb corsair xms ddr3 ram, intel i7 960 cpu, and ati hd 5970. I'm also using a coolmaster haf92 case. My OS is vista X64. Here is my issue when I type in dxdiag in (Start Search) and I look into display. I see in (approx total memory) 716mb graphic memory. The ati hd 5970 is a 2gb graphic card. Am I being stuipd or is there an issue.

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  • Ubuntu server header timeout

    - by Tabatha M
    I'm running Ubuntu Linux 12.04.1 Kernel and CPU Linux 3.2.0-30-generic on x86_64. Intel(R) Xeon(R) CPU E31230 @ 3.20GHz, 8 cores I recently came across this problem. I'm using apache2/php latest and when I run $url_headers = @get_headers($url); Inside PHP it would normally take milliseconds to within a second to get the headers. Now recently it can take up to 15 seconds or even timeout. It has worked great for over a year and recently started doing this. I'm not sure how to go about fixing it, any help would be greatly appreciated. Thank you

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  • Server spec for a small business [duplicate]

    - by I'll-Be-Back
    This question already has an answer here: Can you help me with my capacity planning? 2 answers I will need to buy a decent server for Windows Server 2012 and Linux for Web server (Internal use only - Intranet). I will install ESXi with 2 or 3 VM's. There will be about 80-100 Agents at work, they will login (domain controller) on client PC in the morning (between 9:40am to 10:05am). They can only use IE browser and everything else will be locked. They will not have any storage space, no email, etc. Is this spec decent enough? 2u Supermicro 825 chassis, X9SCL-F x1 Intel E3-1290v2 16Gb DDR3 x2 Intel 520 Series 240Gb x2 2Tb Seagate Barracuda, LSi 4 port SAS raid controller

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  • Site faster on 1 core/1GB ram than on 8 core/32GB ram wth?

    - by xtra
    Both sites are US based. I'm located in Europe. http://198.105.209.13/ <==== site that loads tons faster on 1 core and 1gb ram ONLY (Cent OS VPS) http://108.61.35.219/ <== site is located on my dedicated server with i7-3770 cpu and 32 gb ram (Windows) and is slow as hell Even if faster site is on linux it shouldn't make such a big difference in page load seriously. Does anyone know what could be a hiccup on the dedicated server? It's just unbelievable to me that site loads faster on 1 core cpu than on dedicated server. Note that site is pretty much only thing running on dedicated server. It has 1gbps connection.

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  • Why do some servers have so many processes running?

    - by Xeoncross
    I have two VPS servers but they have drastically different amounts of memory usage and processes running. I'm still new to running linux servers so I'm having trouble figuring out what is going on and what I can do to fix it. Both are Debian 5 32bit installs. On one server with 128MB of ram and a single CPU core I have a full server running in only 84MB of RAM. The other server has 512MB (quad core CPU) and it has nothing running but core processes yet its still using 94MB of RAM. Does one have a different kind of virtualization technology that requires more linux core processes or what?

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  • What can i do when my Ubuntu stucked [closed]

    - by Avihai Marchiano
    From time to time firefox cause to my Ubuntu machine to stuck.(nothing run on the machine except firefox) I cant move the mouse or move windows by keyboard. In some cases i have wait for a few minutes and than close last open tab in firefox and it solve the problem in other cases i do restart. Is there any way to prevent it, limit forefox in some way? In windows in most cased even with 100% cpu you can do alt-ctrl-delete and get the task manager, is there a top priority combination in linux that give you terminal? Or any other way ... Run on Ubuntux86 with GNOME , 2GB RAM, dual core cpu

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  • SQL SERVER – Configure Management Data Collection in Quick Steps – T-SQL Tuesday #005

    - by pinaldave
    This article was written as a response to T-SQL Tuesday #005 – Reporting. The three most important components of any computer and server are the CPU, Memory, and Hard disk specification. This post talks about  how to get more details about these three most important components using the Management Data Collection. Management Data Collection generates the reports for the three said components by default. Configuring Data Collection is a very easy task and can be done very quickly. Please note: There are many different ways to get reports generated for CPU, Memory and IO. You can use DMVs, Extended Events as well Perfmon to trace the data. Keeping the T-SQL Tuesday subject of reporting this post is created to give visual tutorial to quickly configure Data Collection and generate Reports. From Book On-Line: The data collector is a core component of the Data Collection platform for SQL Server 2008 and the tools that are provided by SQL Server. The data collector provides one central point for data collection across your database servers and applications. This collection point can obtain data from a variety of sources and is not limited to performance data, unlike SQL Trace. Let us go over the visual tutorial on how quickly Data Collection can be configured. Expand the management node under the main server node and follow the direction in the pictures. This reports can be exported to PDF as well Excel by writing clicking on reports. Now let us see more additional screenshots of the reports. The reports are very self-explanatory  but can be drilled down to get further details. Click on the image to make it larger. Well, as we can see, it is very easy to configure and utilize this tool. Do you use this tool in your organization? Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: SQL Reporting, SQL Reports

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  • SQL SERVER – Identify Most Resource Intensive Queries – SQL in Sixty Seconds #028 – Video

    - by pinaldave
    During performance tuning conversation the very first question people often ask is what are the queries offending the server or in another word let us identify the queries which are the most resource intensive. The resources are often described as either Memory, CPU or IO. When we talk about the queries the same is applicable for them as well. The query which is doing lots of reads or writes are for sure resource intensive as well query which are taking maximum CPU time. Performance tuning is a very deep subject and we all have our own preference regarding what should be the first step to tuning and what should be looked with the salt of grain. Though there is no denying that a query which uses more resources than what it should be using for sure require tuning. There are many ways to do identify query using intense resources (e.g. Extended events etc) but in this one we will go by simple DMV. There is a small gotcha we all have to remember about usage of DMV is that it only brings back results from existing cache. So if you have a query which is very resource intensive but is not cached or if you have explicitly removed the query from the cache it will be not part of the result returned by this DMV. It is quite possible that a query is aged and removed from the cache if your cache is not huge. If your cache is large you may want to be careful in running this query during business hours as this query itself can be resource intensive. Get Script to identify resource intensive query from Here Related Tips in SQL in Sixty Seconds: SQL SERVER – Find Most Expensive Queries Using DMV Simple Example to Configure Resource Governor – Introduction to Resource Governor SQL SERVER – DMV – sys.dm_exec_query_optimizer_info – Statistics of Optimizer SQL SERVER – Wait Stats – Wait Types – Wait Queues – Day 0 of 28 Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL in Sixty Seconds, SQL Query, SQL Scripts, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology, Video Tagged: Excel

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  • Option Trading: Getting the most out of the event session options

    - by extended_events
    You can control different aspects of how an event session behaves by setting the event session options as part of the CREATE EVENT SESSION DDL. The default settings for the event session options are designed to handle most of the common event collection situations so I generally recommend that you just use the defaults. Like everything in the real world though, there are going to be a handful of “special cases” that require something different. This post focuses on identifying the special cases and the correct use of the options to accommodate those cases. There is a reason it’s called Default The default session options specify a total event buffer size of 4 MB with a 30 second latency. Translating this into human terms; this means that our default behavior is that the system will start processing events from the event buffer when we reach about 1.3 MB of events or after 30 seconds, which ever comes first. Aside: What’s up with the 1.3 MB, I thought you said the buffer was 4 MB?The Extended Events engine takes the total buffer size specified by MAX_MEMORY (4MB by default) and divides it into 3 equally sized buffers. This is done so that a session can be publishing events to one buffer while other buffers are being processed. There are always at least three buffers; how to get more than three is covered later. Using this configuration, the Extended Events engine can “keep up” with most event sessions on standard workloads. Why is this? The fact is that most events are small, really small; on the order of a couple hundred bytes. Even when you start considering events that carry dynamically sized data (eg. binary, text, etc.) or adding actions that collect additional data, the total size of the event is still likely to be pretty small. This means that each buffer can likely hold thousands of events before it has to be processed. When the event buffers are finally processed there is an economy of scale achieved since most targets support bulk processing of the events so they are processed at the buffer level rather than the individual event level. When all this is working together it’s more likely that a full buffer will be processed and put back into the ready queue before the remaining buffers (remember, there are at least three) are full. I know what you’re going to say: “My server is exceptional! My workload is so massive it defies categorization!” OK, maybe you weren’t going to say that exactly, but you were probably thinking it. The point is that there are situations that won’t be covered by the Default, but that’s a good place to start and this post assumes you’ve started there so that you have something to look at in order to determine if you do have a special case that needs different settings. So let’s get to the special cases… What event just fired?! How about now?! Now?! If you believe the commercial adage from Heinz Ketchup (Heinz Slow Good Ketchup ad on You Tube), some things are worth the wait. This is not a belief held by most DBAs, particularly DBAs who are looking for an answer to a troubleshooting question fast. If you’re one of these anxious DBAs, or maybe just a Program Manager doing a demo, then 30 seconds might be longer than you’re comfortable waiting. If you find yourself in this situation then consider changing the MAX_DISPATCH_LATENCY option for your event session. This option will force the event buffers to be processed based on your time schedule. This option only makes sense for the asynchronous targets since those are the ones where we allow events to build up in the event buffer – if you’re using one of the synchronous targets this option isn’t relevant. Avoid forgotten events by increasing your memory Have you ever had one of those days where you keep forgetting things? That can happen in Extended Events too; we call it dropped events. In order to optimizes for server performance and help ensure that the Extended Events doesn’t block the server if to drop events that can’t be published to a buffer because the buffer is full. You can determine if events are being dropped from a session by querying the dm_xe_sessions DMV and looking at the dropped_event_count field. Aside: Should you care if you’re dropping events?Maybe not – think about why you’re collecting data in the first place and whether you’re really going to miss a few dropped events. For example, if you’re collecting query duration stats over thousands of executions of a query it won’t make a huge difference to miss a couple executions. Use your best judgment. If you find that your session is dropping events it means that the event buffer is not large enough to handle the volume of events that are being published. There are two ways to address this problem. First, you could collect fewer events – examine you session to see if you are over collecting. Do you need all the actions you’ve specified? Could you apply a predicate to be more specific about when you fire the event? Assuming the session is defined correctly, the next option is to change the MAX_MEMORY option to a larger number. Picking the right event buffer size might take some trial and error, but a good place to start is with the number of dropped events compared to the number you’ve collected. Aside: There are three different behaviors for dropping events that you specify using the EVENT_RETENTION_MODE option. The default is to allow single event loss and you should stick with this setting since it is the best choice for keeping the impact on server performance low.You’ll be tempted to use the setting to not lose any events (NO_EVENT_LOSS) – resist this urge since it can result in blocking on the server. If you’re worried that you’re losing events you should be increasing your event buffer memory as described in this section. Some events are too big to fail A less common reason for dropping an event is when an event is so large that it can’t fit into the event buffer. Even though most events are going to be small, you might find a condition that occasionally generates a very large event. You can determine if your session is dropping large events by looking at the dm_xe_sessions DMV once again, this time check the largest_event_dropped_size. If this value is larger than the size of your event buffer [remember, the size of your event buffer, by default, is max_memory / 3] then you need a large event buffer. To specify a large event buffer you set the MAX_EVENT_SIZE option to a value large enough to fit the largest event dropped based on data from the DMV. When you set this option the Extended Events engine will create two buffers of this size to accommodate these large events. As an added bonus (no extra charge) the large event buffer will also be used to store normal events in the cases where the normal event buffers are all full and waiting to be processed. (Note: This is just a side-effect, not the intended use. If you’re dropping many normal events then you should increase your normal event buffer size.) Partitioning: moving your events to a sub-division Earlier I alluded to the fact that you can configure your event session to use more than the standard three event buffers – this is called partitioning and is controlled by the MEMORY_PARTITION_MODE option. The result of setting this option is fairly easy to explain, but knowing when to use it is a bit more art than science. First the science… You can configure partitioning in three ways: None, Per NUMA Node & Per CPU. This specifies the location where sets of event buffers are created with fairly obvious implication. There are rules we follow for sub-dividing the total memory (specified by MAX_MEMORY) between all the event buffers that are specific to the mode used: None: 3 buffers (fixed)Node: 3 * number_of_nodesCPU: 2.5 * number_of_cpus Here are some examples of what this means for different Node/CPU counts: Configuration None Node CPU 2 CPUs, 1 Node 3 buffers 3 buffers 5 buffers 6 CPUs, 2 Node 3 buffers 6 buffers 15 buffers 40 CPUs, 5 Nodes 3 buffers 15 buffers 100 buffers   Aside: Buffer size on multi-processor computersAs the number of Nodes or CPUs increases, the size of the event buffer gets smaller because the total memory is sub-divided into more pieces. The defaults will hold up to this for a while since each buffer set is holding events only from the Node or CPU that it is associated with, but at some point the buffers will get too small and you’ll either see events being dropped or you’ll get an error when you create your session because you’re below the minimum buffer size. Increase the MAX_MEMORY setting to an appropriate number for the configuration. The most likely reason to start partitioning is going to be related to performance. If you notice that running an event session is impacting the performance of your server beyond a reasonably expected level [Yes, there is a reasonably expected level of work required to collect events.] then partitioning might be an answer. Before you partition you might want to check a few other things: Is your event retention set to NO_EVENT_LOSS and causing blocking? (I told you not to do this.) Consider changing your event loss mode or increasing memory. Are you over collecting and causing more work than necessary? Consider adding predicates to events or removing unnecessary events and actions from your session. Are you writing the file target to the same slow disk that you use for TempDB and your other high activity databases? <kidding> <not really> It’s always worth considering the end to end picture – if you’re writing events to a file you can be impacted by I/O, network; all the usual stuff. Assuming you’ve ruled out the obvious (and not so obvious) issues, there are performance conditions that will be addressed by partitioning. For example, it’s possible to have a successful event session (eg. no dropped events) but still see a performance impact because you have many CPUs all attempting to write to the same free buffer and having to wait in line to finish their work. This is a case where partitioning would relieve the contention between the different CPUs and likely reduce the performance impact cause by the event session. There is no DMV you can check to find these conditions – sorry – that’s where the art comes in. This is  largely a matter of experimentation. On the bright side you probably won’t need to to worry about this level of detail all that often. The performance impact of Extended Events is significantly lower than what you may be used to with SQL Trace. You will likely only care about the impact if you are trying to set up a long running event session that will be part of your everyday workload – sessions used for short term troubleshooting will likely fall into the “reasonably expected impact” category. Hey buddy – I think you forgot something OK, there are two options I didn’t cover: STARTUP_STATE & TRACK_CAUSALITY. If you want your event sessions to start automatically when the server starts, set the STARTUP_STATE option to ON. (Now there is only one option I didn’t cover.) I’m going to leave causality for another post since it’s not really related to session behavior, it’s more about event analysis. - Mike Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • system overrides my mount parameters in /etc/fstab

    - by valya
    [.../~]$ mount /dev/sda4 on / type ext4 (rw,commit=60,commit=0) [.../~]$ cat /etc/fstab # UNCONFIGURED FSTAB FOR BASE SYSTEM UUID=70739c04-fcb6-4747-803c-824f9c894f41 / ext4 defaults,commit=60 0 1 What can I do about it? It seems strange. I want to be able to set any commit time I want Edit: added /proc/mounts contents [.../~]$ cat /proc/mounts rootfs / rootfs rw 0 0 none /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0 none /proc proc rw,nosuid,nodev,noexec,relatime 0 0 none /dev devtmpfs rw,relatime,size=886332k,nr_inodes=221583,mode=755 0 0 none /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0 fusectl /sys/fs/fuse/connections fusectl rw,relatime 0 0 /dev/disk/by-uuid/70739c04-fcb6-4747-803c-824f9c894f41 / ext4 rw,relatime,barrier=1,data=ordered 0 0 none /sys/kernel/debug debugfs rw,relatime 0 0 none /sys/kernel/security securityfs rw,relatime 0 0 none /dev/shm tmpfs rw,nosuid,nodev,relatime 0 0 none /var/run tmpfs rw,nosuid,relatime,mode=755 0 0 none /var/lock tmpfs rw,nosuid,nodev,noexec,relatime 0 0 /dev/sda3 /media/megahard fuseblk rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other,blksize=4096 0 0 cgroup /dev/cgroup/cpu cgroup rw,relatime,cpu,release_agent=/usr/local/sbin/cgroup_clean 0 0 gvfs-fuse-daemon /home/va1en0k/.gvfs fuse.gvfs-fuse-daemon rw,nosuid,nodev,relatime,user_id=1000,group_id=1000 0 0

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  • Is recursion really bad?

    - by dotneteer
    After my previous post about the stack space, it appears that there is perception from the feedback that recursion is bad and we should avoid deep recursion. After writing a compiler, I know that the modern computer and compiler are complex enough and one cannot automatically assume that a hand crafted code would out-perform the compiler optimization. The only way is to do some prototype to find out. So why recursive code may not perform as well? Compilers place frames on a stack. In additional to arguments and local variables, compiles also need to place frame and program pointers on the frame, resulting in overheads. So why hand-crafted code may not performance as well? The stack used by a compiler is a simpler data structure and can grow and shrink cleanly. To replace recursion with out own stack, our stack is allocated in the heap that is far more complicated to manage. There could be overhead as well if the compiler needs to mark objects for garbage collection. Compiler also needs to worry about the memory fragmentation. Then there is additional complexity: CPUs have registers and multiple levels of cache. Register access is a few times faster than in-CPU cache access and is a few 10s times than on-board memory access. So it is up to the OS and compiler to maximize the use of register and in-CPU cache. For my particular problem, I did an experiment to rewrite my c# version of recursive code with a loop and stack approach. So here are the outcomes of the two approaches:   Recursive call Loop and Stack Lines of code for the algorithm 17 46 Speed Baseline 3% faster Readability Clean Far more complex So at the end, I was able to achieve 3% better performance with other drawbacks. My message is never assuming your sophisticated approach would automatically work out better than a simpler approach with a modern computer and compiler. Gage carefully before committing to a more complex approach.

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  • Option Trading: Getting the most out of the event session options

    - by extended_events
    You can control different aspects of how an event session behaves by setting the event session options as part of the CREATE EVENT SESSION DDL. The default settings for the event session options are designed to handle most of the common event collection situations so I generally recommend that you just use the defaults. Like everything in the real world though, there are going to be a handful of “special cases” that require something different. This post focuses on identifying the special cases and the correct use of the options to accommodate those cases. There is a reason it’s called Default The default session options specify a total event buffer size of 4 MB with a 30 second latency. Translating this into human terms; this means that our default behavior is that the system will start processing events from the event buffer when we reach about 1.3 MB of events or after 30 seconds, which ever comes first. Aside: What’s up with the 1.3 MB, I thought you said the buffer was 4 MB?The Extended Events engine takes the total buffer size specified by MAX_MEMORY (4MB by default) and divides it into 3 equally sized buffers. This is done so that a session can be publishing events to one buffer while other buffers are being processed. There are always at least three buffers; how to get more than three is covered later. Using this configuration, the Extended Events engine can “keep up” with most event sessions on standard workloads. Why is this? The fact is that most events are small, really small; on the order of a couple hundred bytes. Even when you start considering events that carry dynamically sized data (eg. binary, text, etc.) or adding actions that collect additional data, the total size of the event is still likely to be pretty small. This means that each buffer can likely hold thousands of events before it has to be processed. When the event buffers are finally processed there is an economy of scale achieved since most targets support bulk processing of the events so they are processed at the buffer level rather than the individual event level. When all this is working together it’s more likely that a full buffer will be processed and put back into the ready queue before the remaining buffers (remember, there are at least three) are full. I know what you’re going to say: “My server is exceptional! My workload is so massive it defies categorization!” OK, maybe you weren’t going to say that exactly, but you were probably thinking it. The point is that there are situations that won’t be covered by the Default, but that’s a good place to start and this post assumes you’ve started there so that you have something to look at in order to determine if you do have a special case that needs different settings. So let’s get to the special cases… What event just fired?! How about now?! Now?! If you believe the commercial adage from Heinz Ketchup (Heinz Slow Good Ketchup ad on You Tube), some things are worth the wait. This is not a belief held by most DBAs, particularly DBAs who are looking for an answer to a troubleshooting question fast. If you’re one of these anxious DBAs, or maybe just a Program Manager doing a demo, then 30 seconds might be longer than you’re comfortable waiting. If you find yourself in this situation then consider changing the MAX_DISPATCH_LATENCY option for your event session. This option will force the event buffers to be processed based on your time schedule. This option only makes sense for the asynchronous targets since those are the ones where we allow events to build up in the event buffer – if you’re using one of the synchronous targets this option isn’t relevant. Avoid forgotten events by increasing your memory Have you ever had one of those days where you keep forgetting things? That can happen in Extended Events too; we call it dropped events. In order to optimizes for server performance and help ensure that the Extended Events doesn’t block the server if to drop events that can’t be published to a buffer because the buffer is full. You can determine if events are being dropped from a session by querying the dm_xe_sessions DMV and looking at the dropped_event_count field. Aside: Should you care if you’re dropping events?Maybe not – think about why you’re collecting data in the first place and whether you’re really going to miss a few dropped events. For example, if you’re collecting query duration stats over thousands of executions of a query it won’t make a huge difference to miss a couple executions. Use your best judgment. If you find that your session is dropping events it means that the event buffer is not large enough to handle the volume of events that are being published. There are two ways to address this problem. First, you could collect fewer events – examine you session to see if you are over collecting. Do you need all the actions you’ve specified? Could you apply a predicate to be more specific about when you fire the event? Assuming the session is defined correctly, the next option is to change the MAX_MEMORY option to a larger number. Picking the right event buffer size might take some trial and error, but a good place to start is with the number of dropped events compared to the number you’ve collected. Aside: There are three different behaviors for dropping events that you specify using the EVENT_RETENTION_MODE option. The default is to allow single event loss and you should stick with this setting since it is the best choice for keeping the impact on server performance low.You’ll be tempted to use the setting to not lose any events (NO_EVENT_LOSS) – resist this urge since it can result in blocking on the server. If you’re worried that you’re losing events you should be increasing your event buffer memory as described in this section. Some events are too big to fail A less common reason for dropping an event is when an event is so large that it can’t fit into the event buffer. Even though most events are going to be small, you might find a condition that occasionally generates a very large event. You can determine if your session is dropping large events by looking at the dm_xe_sessions DMV once again, this time check the largest_event_dropped_size. If this value is larger than the size of your event buffer [remember, the size of your event buffer, by default, is max_memory / 3] then you need a large event buffer. To specify a large event buffer you set the MAX_EVENT_SIZE option to a value large enough to fit the largest event dropped based on data from the DMV. When you set this option the Extended Events engine will create two buffers of this size to accommodate these large events. As an added bonus (no extra charge) the large event buffer will also be used to store normal events in the cases where the normal event buffers are all full and waiting to be processed. (Note: This is just a side-effect, not the intended use. If you’re dropping many normal events then you should increase your normal event buffer size.) Partitioning: moving your events to a sub-division Earlier I alluded to the fact that you can configure your event session to use more than the standard three event buffers – this is called partitioning and is controlled by the MEMORY_PARTITION_MODE option. The result of setting this option is fairly easy to explain, but knowing when to use it is a bit more art than science. First the science… You can configure partitioning in three ways: None, Per NUMA Node & Per CPU. This specifies the location where sets of event buffers are created with fairly obvious implication. There are rules we follow for sub-dividing the total memory (specified by MAX_MEMORY) between all the event buffers that are specific to the mode used: None: 3 buffers (fixed)Node: 3 * number_of_nodesCPU: 2.5 * number_of_cpus Here are some examples of what this means for different Node/CPU counts: Configuration None Node CPU 2 CPUs, 1 Node 3 buffers 3 buffers 5 buffers 6 CPUs, 2 Node 3 buffers 6 buffers 15 buffers 40 CPUs, 5 Nodes 3 buffers 15 buffers 100 buffers   Aside: Buffer size on multi-processor computersAs the number of Nodes or CPUs increases, the size of the event buffer gets smaller because the total memory is sub-divided into more pieces. The defaults will hold up to this for a while since each buffer set is holding events only from the Node or CPU that it is associated with, but at some point the buffers will get too small and you’ll either see events being dropped or you’ll get an error when you create your session because you’re below the minimum buffer size. Increase the MAX_MEMORY setting to an appropriate number for the configuration. The most likely reason to start partitioning is going to be related to performance. If you notice that running an event session is impacting the performance of your server beyond a reasonably expected level [Yes, there is a reasonably expected level of work required to collect events.] then partitioning might be an answer. Before you partition you might want to check a few other things: Is your event retention set to NO_EVENT_LOSS and causing blocking? (I told you not to do this.) Consider changing your event loss mode or increasing memory. Are you over collecting and causing more work than necessary? Consider adding predicates to events or removing unnecessary events and actions from your session. Are you writing the file target to the same slow disk that you use for TempDB and your other high activity databases? <kidding> <not really> It’s always worth considering the end to end picture – if you’re writing events to a file you can be impacted by I/O, network; all the usual stuff. Assuming you’ve ruled out the obvious (and not so obvious) issues, there are performance conditions that will be addressed by partitioning. For example, it’s possible to have a successful event session (eg. no dropped events) but still see a performance impact because you have many CPUs all attempting to write to the same free buffer and having to wait in line to finish their work. This is a case where partitioning would relieve the contention between the different CPUs and likely reduce the performance impact cause by the event session. There is no DMV you can check to find these conditions – sorry – that’s where the art comes in. This is  largely a matter of experimentation. On the bright side you probably won’t need to to worry about this level of detail all that often. The performance impact of Extended Events is significantly lower than what you may be used to with SQL Trace. You will likely only care about the impact if you are trying to set up a long running event session that will be part of your everyday workload – sessions used for short term troubleshooting will likely fall into the “reasonably expected impact” category. Hey buddy – I think you forgot something OK, there are two options I didn’t cover: STARTUP_STATE & TRACK_CAUSALITY. If you want your event sessions to start automatically when the server starts, set the STARTUP_STATE option to ON. (Now there is only one option I didn’t cover.) I’m going to leave causality for another post since it’s not really related to session behavior, it’s more about event analysis. - Mike Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • XP Mode (Windows Virtual PC for Windows 7) no longer requires hardware virtualisation - hurrah !

    - by Liam Westley
    Windows Virtual PC (aka XP Mode) When XP Mode was released, it insisted on hardware virtualisation being present on your CPU and enabled in the BIOS.  Given that Windows Virtual PC was based on an improved Virtual PC 2007, which provided hardware virtualisation as a user selectable option, I did wonder why on earth Microsoft thought this was a good idea.  Not only do many people not have a CPU with hardware virtualisation support, some manufacturers don't provide a BIOS option to enable this setting, especially on laptops - yes Sony, Toshiba and Acer, I'm looking at you. Dumb and dumber This issue became a double whammy; not only was Microsoft a bit dumb on not supporting Windows Virtual PC without hardware virtualisation, your hardware manufacturer was also dumb in not supporting the option in the BIOS. Microsoft update to Windows Virtual PC Belatedly, Microsoft has seen the problem with this hardware virtualisation requirement and has now released a new version of Windows Virtual PC that works without hardware virtualisation.  This is really good news for those with older (or limited) CPUs and rubbish BIOS firmware. You can details of how to download the new versions of XP Mode here, http://blogs.msdn.com/virtual_pc_guy/archive/2010/03/18/windows-virtual-pc-no-hardware-virtualization-update-now-available-for-download.aspx And there is also an explanation of why the hardware virtualisation requirement was in place for previous releases, http://blogs.msdn.com/virtual_pc_guy/archive/2010/03/18/windows-virtual-pc-now-without-the-need-for-hardware-virtualization.aspx

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  • Why can I not map a dynamic texture in D3D?

    - by sebf
    I am trying to map a Texture2D resource in DirectX11 via SharpDX. The resource is declared as a ShaderResource, with Dynamic usage and the 'Write' CPU flag specified. My call however fails with a generic exception from SharpDX: _Parent.Context.MapSubresource( _Resource, 0, SharpDX.Direct3D11.MapMode.Write, SharpDX.Direct3D11.MapFlags.None, out stream ); I see from this question that it is supported. The MSDN docs and this other question hint that instead of using Context.MapSubresource() I should be using Texture2D.Map(), however, the DirectX11 Texture2D class does not define Map() (though it does for the D3D 10 equivalent). If I call the above with MapMode.WriteDiscard, the call succeeds but in this case the previous content of the texture is lost, which is no good when I only want to update a section of it. Has the Map() method been removed in Direct3D 11 or am I looking in the wrong place? Is the MapSubresource() method unsuitable or am I using it wrong? EDIT: I declared my resource as Dynamic with CPU Write Flags - not Default as I originaly wrote - sorry for the fairly huge 'typo' that changes the entire question!

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  • Workshop in Holland - and open questions

    - by Mike Dietrich
    Thanks to everybody visiting yesterday the Upgrade Workshop in Maarsen. I had lots of fun - and I hope you'd enjoy it, too :-) The slides, as always, can be downloaded from: http://apex.oracle.com/folien Use the Schluesselwort/Keyword: upgrade112 And thanks to all those of you sending feedback regarding "traget/destination" (will change it in the slides) and other topics such as Enterprise Manager Grid Control 11g. Enterprise Manager 11g will be launched on 22-APR-2010 - and you can join the event live if you will be accidentialy in New York:http://www.oracle.com/enterprisemanager11g/index.html Thanks for this hint!!! Regarding the open questions: Will there be PSUs available for Intel Solaris? PSUs will be made available on nearly all platforms including Intel Solaris. Please see Note:882604.1 for platform information and Note:854428.1 for direct links to the PSU download location. Is COMMIT_WRITE=NOWAIT the default in patch set 10.2.0.4? I tried to verify this and neither couldn't find a bug entry nor a documentation saying the 10.2.0.4 has a different default setting (default behaviour is WAIT). Checked it in my 10.2.0.4 instances as well and there it is set to WAIT. If this parameter is not explicitly specified, then database commit behavior defaults to writing commit records to disk before control is returned to the client. If only IMMEDIATE or BATCH is specified, but not WAIT or NOWAIT, then WAIT mode is assumed. If only WAIT or NOWAIT is specified, but not IMMEDIATE or BATCH, then IMMEDIATE mode is assumed Please feedback to me if you have different experiences. Service Request escalation by telephone? Thanks for this update - I didn't realize that ;-) Now I know why it hasn't helped last month when I've updated an SR ... here's the official information on that: Note:199389.1 - Note has been updated on 24-FEB-2010. See the telephone number to Oracle support to request an escalation here: http://www.oracle.com/support/contact.html

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  • Bluetooth not working on an Alienware m14x r2

    - by S. L.
    on my alienware m14x r2 laptop with ubuntu 12.04.1 x64, the bluetooth interface is not working. WLAN works fine. I have a dualboot install with ubuntu & win 7 on this laptop. In win 7, the bluetooth interface works fine, because its all activated in BIOS. I have the killer wireless-n 1202 a/g/n interface with integrated bluetooth 4.0 in this laptop. Here is some code : sudo rfkill list 0: phy0: Wireless LAN Soft blocked: no Hard blocked: no lsusb Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub Bus 001 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 002: ID 8087:0024 Intel Corp. Integrated Rate Matching Hub Bus 001 Device 003: ID 064e:8128 Suyin Corp. Bus 002 Device 003: ID 0cf3:3004 Atheros Communications, Inc. Bus 002 Device 004: ID 187c:0521 Alienware Corporation dmesg | grep "Bluetooth" [ 2.590377] Bluetooth: Core ver 2.16 [ 2.590395] Bluetooth: HCI device and connection manager initialized [ 2.590397] Bluetooth: HCI socket layer initialized [ 2.590399] Bluetooth: L2CAP socket layer initialized [ 2.590403] Bluetooth: SCO socket layer initialized [ 2.591518] Bluetooth: BNEP (Ethernet Emulation) ver 1.3 [ 2.591519] Bluetooth: BNEP filters: protocol multicast [ 2.599411] Bluetooth: RFCOMM TTY layer initialized [ 2.599415] Bluetooth: RFCOMM socket layer initialized [ 2.599416] Bluetooth: RFCOMM ver 1.11 [ 2.696552] Bluetooth: Generic Bluetooth USB driver ver 0.6 [ 2.696751] Bluetooth: Atheros AR30xx firmware driver ver 1.0 [ 2.702607] Bluetooth: Configuration file not found ar3k/ramps_0x11020000_40.dfu [ 2.702609] Bluetooth: Loading sysconfig file failed Any ideas to fix that problem ?

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