cpu - Page 24 - Developer IT

Is CPU execution time different in Loop with Sleep() and Long Loops without sleep(), with both havin

- by Jagira

Hello, I have a loop that runs for approx. 25 minutes i.e 1500 seconds. [100 loops with sleep(15)] The execution time for the statements inside loop is very less. My scripts are hosted on GoDaddy. I am sure that they are having some kind of limit on execution time. My question is, are they concerned with "the total CPU execution time" or the total running time.

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Programmatically limit CPU usage by any application on Windows 7?

- by user259878

Hi, I'm looking for a way to limit the CPU usage by any application on Windows 7 to 50%. I've tried searching the Internet for a way to do this, and it looks like this is an easy thing to do on Linux and Mac OS X (one command in the terminal) but I'm not sure how to do it on Windows 7. Any help would be much appreciated. Thanks! Rohan

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How do I get CPU Clock Speed in C++ (Linux)?

- by naspinski

How can I get the CPU clock speed in C++? I am running Ubuntu 9.10 if that makes any difference.

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Is there a way to reliably detect the total number of CPU cores?

- by John Sheares

I need a reliable way to detect how many CPU cores are on a computer. I am creating a numerically intense simulation C# application and want to create the maximum number of running threads as cores. I have tried many of the methods suggested around the internet like Environment.ProcessorCount, using WMI, this code: http://blogs.adamsoftware.net/Engine/DeterminingthenumberofphysicalCPUsonWindows.aspx. None of them seem to think a AMD X2 has two cores. Any ideas?

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how to open many tabs in chromium but unload/disable inactive/notCurrent ones, releasing memory and cpu?

- by Aquarius Power

So I have 50 tabs opened on chromium, but that is using too much memory and some of the CPU. How can I have all those concurrent researches I am doing opened but not clog my machine? I think there should have a way that only the active tab is loaded in memory and running, and all the others should stay closed/unloaded from memory, until I want to look at them... Any extension can do something like that?

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What does "cpuid level" means ? Asking just for curiosity

- by ogzylz

For example, I put just 2 core info of a 16 core machine. What does "cpuid level : 6" line means? If u can provide info about lines "bogomips : 5992.10" and "clflush size : 64" I will be appreciated processor : 0 vendor_id : GenuineIntel cpu family : 15 model : 6 model name : Intel(R) Xeon(TM) CPU 3.00GHz stepping : 8 cpu MHz : 2992.689 cache size : 4096 KB physical id : 0 siblings : 4 core id : 0 cpu cores : 2 fpu : yes fpu_exception : yes cpuid level : 6 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx cid cx16 xtpr lahf_lm bogomips : 5992.10 clflush size : 64 cache_alignment : 128 address sizes : 40 bits physical, 48 bits virtual power management: processor : 1 vendor_id : GenuineIntel cpu family : 15 model : 6 model name : Intel(R) Xeon(TM) CPU 3.00GHz stepping : 8 cpu MHz : 2992.689 cache size : 4096 KB physical id : 1 siblings : 4 core id : 0 cpu cores : 2 fpu : yes fpu_exception : yes cpuid level : 6 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx lm constant_tsc pni monitor ds_cpl vmx cid cx16 xtpr lahf_lm bogomips : 5985.23 clflush size : 64 cache_alignment : 128 address sizes : 40 bits physical, 48 bits virtual power management:

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Drawing particles with CPU instead of GPU (XNA)

- by Helix

I'm trying out modifications to the following particle system. http://create.msdn.com/en-US/education/catalog/sample/particle_3d I have a function such that when I press Space, all the particles have their positions and velocities set to 0. for (int i = 0; i < particles.GetLength(0); i++) { particles[i].Position = Vector3.Zero; particles[i].Velocity = Vector3.Zero; } However, when I press space, the particles are still moving. If I go to FireParticleSystem.cs I can turn settings.Gravity to 0 and the particles stop moving, but the particles are still not being shifted to (0,0,0). As I understand it, the problem lies in the fact that the GPU is processing all the particle positions, and it's calculating where the particles should be based on their initial position, their initial velocity and multiplying by their age. Therefore, all I've been able to do is change the initial position and velocity of particles, but I'm unable to do it on the fly since the GPU is handling everything. I want the CPU to calculate the positions of the particles individually. This is because I will be later implementing some sort of wind to push the particles around. How do I stop the GPU from taking over? I think it's something to do with VertexBuffers and the draw function, but I don't know how to modify it to make it work.

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check what process was causing the problem of high cpu load

- by linuxk

I'm running nginx wordpress server in KVM using 12.04 server x86. It was running very well about 4 month until 2 hours ago. I found that my website is down and no ping response. Virt-manager logged high cpu load(plz see the picture below) before unexpected shut down. I want to know what process caused unexpected shutdown. The following log files make me think my server is attacked. Any suggestions and help would be appreciated. kern.log and syslog showed me same output. Nov 11 03:54:11 www kernel: [1344541.156239] [UFW BLOCK] IN=eth0 OUT= MAC= SRC=0.0.0.0 DST=224.0. 0.1 LEN=32 TOS=0x00 PREC=0xC0 TTL=1 ID=0 DF PROTO=2 Nov 11 03:54:11 www kernel: [1344541.156315] [UFW BLOCK] IN=eth0 OUT= MAC= SRC=0101:080a:2334:c90 0:0100:0000:0000:0000 DST=ff02:0000:0000:0000:0000:0000:0000:0001 LEN=72 TC=0 HOPLIMIT=1 FLOWLBL=0 PROTO=ICMPv6 TYPE=130 CODE=0 /nginx/access.log showed me 119.235.237.17 - - [11/Nov/2012:03:45:29 +0900] "GET /blog HTTP/1.1" 200 30493 "-" "Yeti/1.0 (NHN Corp.; http://help.naver.com/robots/)" my-server-ip - - [11/Nov/2012:11:05:30 +0900] "POST /wp-cron.php?doing_wp_cron=13 HTTP/1.0" 499 0 "-" "WordPress/3.4.2; http://mywebsite.com" Server turned on in here. 119.235.237.16 - - [11/Nov/2012:11:05:30 +0900] "GET /blog HTTP/1.1" 200 32935 "-" "Yeti/1.0 (NHN Corp.; http://help.naver.com/robots/)"

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Xna, after mouse click cpu usage goes 100%

- by kosnkov

Hi i have following code and it is enough just if i click on blue window then cpu goes to 100% for like at least one minute even with my i7 4 cores. I just check even with empty project and is the same !!! public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; private Texture2D cursorTex; private Vector2 cursorPos; GraphicsDevice device; float xPosition; float yPosition; public Game1() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; } protected override void Initialize() { Viewport vp = GraphicsDevice.Viewport; xPosition = vp.X + (vp.Width / 2); yPosition = vp.Y + (vp.Height / 2); device = graphics.GraphicsDevice; base.Initialize(); } protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); cursorTex = Content.Load<Texture2D>("strzalka"); } protected override void UnloadContent() { // TODO: Unload any non ContentManager content here } protected override void Update(GameTime gameTime) { // Allows the game to exit if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed) this.Exit(); base.Update(gameTime); } protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.CornflowerBlue); spriteBatch.Begin(); spriteBatch.Draw(cursorTex, cursorPos, Color.White); spriteBatch.End(); base.Draw(gameTime); } }

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Identify high CPU consumed thread for Java app

- by Vincent Ma

Following java code to emulate busy and Idle thread and start it. import java.util.concurrent.*;import java.lang.*; public class ThreadTest { public static void main(String[] args) { new Thread(new Idle(), "Idle").start(); new Thread(new Busy(), "Busy").start(); }}class Idle implements Runnable { @Override public void run() { try { TimeUnit.HOURS.sleep(1); } catch (InterruptedException e) { } }}class Busy implements Runnable { @Override public void run() { while(true) { "Test".matches("T.*"); } }} Using Processor Explorer to get this busy java processor and get Thread id it cost lots of CPU see the following screenshot: Cover to 4044 to Hexadecimal is oxfcc. Using VistulVM to dump thread and get that thread. see the following screenshot In Linux you can use top -H to get Thread information. That it! Any question let me know. Thanks

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Dynamic Monitoring Service (DMS) Configuration Dumping and CPU Utilization

- by ShawnBailey

There was recently a report of CPU spikes on a system that were occuring at precise 3 hour intervals. Research revealed that the spikes were the result of the Dynamic Monitoring Service generating a metrics dump and writing it under the server 'logs' folder for every WLS server in the domain. This blog provides some information on what this is for and how to control it. The Dynamic Monitoring Service is a facility in FMw (JRF to be more precise) that collects runtime data on the components deployed to WebLogic. Each component is responsible for how much or how little they use the service and SOA collects a fair amount of information. To view what is collected on any running server you can use the following URL, http://host:port/dms/Spy and login with admin credentials. DMS is essentially always running and collecting this information in the runtime and to protect against loss of this data it also runs automatic backups, by default at the 3 hour interval mentioned above. Most of the management options for DMS are exposed through WLST but these settings are not so we must open the dms_config.xml file which can be found in DOMAIN_HOME/config/fmwconfig/servers/<server_name>/dms_config.xml. The contents are fairly short and at the bottom you will find the following entry: <dumpConfiguration> <dump intervalSeconds="10800" maxSizeMBytes="75" enabled="true"/> </dumpConfiguration> The interval of 10800 seconds corresponds to the 3 hours and the maximum size is 75MB. The file is written as an archive to DOMAIN_HOME/servers/<server_name>/logs/metrics. This archive contains the dump in XML format. You can disable the dumps all together by simply setting the 'enabled' value to 'false' or of course you could modify the other parameters to suit your needs. Disabling the dumps will NOT impact DMS collections or display at runtime. It will only eliminate these periodic backups.

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Fan always on and overheating problems on HP G62

- by Dave

I have a HP G62 with i5 processor, 4G Ram and ATI HD 5470. Started using Ubuntu 4 months ago, first was 11.10 and after 12.04. Everything worked perfectly until some weeks ago when my cpu fan became "crazy" and I mean by this always on, noise and overheating problems, for sure if I put a glass with water in some minutes will boil (and I mean it). There can be a bug in the last kernel or any other Ubuntu's official update? And by the way CPU fan is cleaned like a new born baby; Used jupiter and all those stuff (lm-sensor, psensor...) - same problem; Don't ask me to install ATI drivers because will work like sh#t (interface laggy as HD 5470 isn't supported by Ubuntu) and I can't even open ATI Catalyst (error when I try to open it), more than this I always used open source drivers and as I said, worked perfectly (3d, effects). Right now I'm back to Windows and everything is working perfectly but my main problem is that I get used with Ubuntu and kinda weird to use windows again. I want back my nice and almost perfect Ubuntu. Thanks, Dave

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Japanese Multiplication simulation - is a program actually capable of improving calculation speed?

- by jt0dd

On SuperUser, I asked a (possibly silly) question about processors using mathematical shortcuts and would like to have a look at the possibility at the software application of that concept. I'd like to write a simulation of Japanese Multiplication to get benchmarks on large calculations utilizing the shortcut vs traditional CPU multiplication. I'm curious as to whether it makes sense to try this. My Question: I'd like to know whether or not a software math shortcut, as described above is actually a shortcut at all. This is a question of programming concept. By utilizing the simulation of Japanese Multiplication, is a program actually capable of improving calculation speed? Or am I doomed from the start? The answer to this question isn't required to determine whether or not the experiment will succeed, but rather whether or not it's logically possible for such a thing to occur in any program, using this concept as an example. My theory is that since addition is computed faster than multiplication, a simulation of Japanese multiplication may actually allow a program to multiply (large) numbers faster than the CPU arithmetic unit can. I think this would be a very interesting finding, if it proves to be true. If, in the multiplication of numbers of any immense size, the shortcut were to calculate the result via less instructions (or faster) than traditional ALU multiplication, I would consider the experiment a success.

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Can certain system-hungry modules be disabled in Ubuntu?

- by Ole Thomsen Buus

Hi, Let me add some context: I am currently using Ubuntu 9.10 64-bit (Desktop) on a relatively powerful stationary PC (Intel Core i7 920, 12GB ram). My purpose is highspeed imaging with a pointgrey Grashopper machine-vision camera (for research, PhD project). This camera is capable of 200 fps at full VGA (640x480) resolution. The camera is connected using Firewire (1394b) and the drivers and software from Pointgrey works great. I have developed a console C++ application that can grap a certain number of frames to preallocated memory and after this also save the grapped frames to harddrive. Currently it works fine but sometimes I am observing a few framedrops (1-3). When this happens I reset the experiment and repeat the recording and usually i am lucky the second time with no framedrops (the camera-driver has a internal framecounter that I am using). Question: I usually go to tty1 and use "sudo service gdm stop" to disable the graphical frontend. It seems to release some memory though that is not my main concern. My concern is CPU resources. Are there other system hungry modules that can be disabled temporarily such that the CPU gets less busy on Ubuntu 9.10? At some point in the future I will update to 10.10. Should I perhaps option for the server edition instead? Thanks.

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Oracle Virtual Server OEL vm fails to start - kernel panic on cpu identify

- by Towndrunk

I am in the process of following a guide to setup various oracle vm templates, so far I have installed OVS 2. 2 and got the OVM Manager working, imported the template for OEL5U5 and created a vm from it.. the problem comes when starting that vm. The log in the OVMM console shows the following; Update VM Status - Running Configure CPU Cap Set CPU Cap: failed:<Exception: failed:<Exception: ['xm', 'sched-credit', '-d', '32_EM11g_OVM', '-c', '0'] => Error: Domain '32_EM11g_OVM' does not exist. StackTrace: File "/opt/ovs-agent-2.3/OVSXXenVMConfig.py", line 2531, in xen_set_cpu_cap run_cmd(args=['xm', File "/opt/ovs-agent-2.3/OVSCommons.py", line 92, in run_cmd raise Exception('%s => %s' % (args, err)) The xend.log shows; [2012-11-12 16:42:01 7581] DEBUG (DevController:139) Waiting for devices vtpm [2012-11-12 16:42:01 7581] INFO (XendDomain:1180) Domain 32_EM11g_OVM (3) unpaused. [2012-11-12 16:42:03 7581] WARNING (XendDomainInfo:1907) Domain has crashed: name=32_EM11g_OVM id=3. [2012-11-12 16:42:03 7581] ERROR (XendDomainInfo:2041) VM 32_EM11g_OVM restarting too fast (Elapsed time: 11.377262 seconds). Refusing to restart to avoid loops .> [2012-11-12 16:42:03 7581] DEBUG (XendDomainInfo:2757) XendDomainInfo.destroy: domid=3 [2012-11-12 16:42:12 7581] DEBUG (XendDomainInfo:2230) Destroying device model [2012-11-12 16:42:12 7581] INFO (image:553) 32_EM11g_OVM device model terminated I have set_on_crash="preserve" in the vm.cfg and have then run xm create -c to get the console screen while booting and this is the log of what happens.. Started domain 32_EM11g_OVM (id=4) Bootdata ok (command line is ro root=LABEL=/ ) Linux version 2.6.18-194.0.0.0.3.el5xen ([email protected]) (gcc version 4.1.2 20080704 (Red Hat 4.1.2-48)) #1 SMP Mon Mar 29 18:27:00 EDT 2010 BIOS-provided physical RAM map: Xen: 0000000000000000 - 0000000180800000 (usable)> No mptable found. Built 1 zonelists. Total pages: 1574912 Kernel command line: ro root=LABEL=/ Initializing CPU#0 PID hash table entries: 4096 (order: 12, 32768 bytes) Xen reported: 1600.008 MHz processor. Console: colour dummy device 80x25 Dentry cache hash table entries: 1048576 (order: 11, 8388608 bytes) Inode-cache hash table entries: 524288 (order: 10, 4194304 bytes) Software IO TLB disabled Memory: 6155256k/6299648k available (2514k kernel code, 135548k reserved, 1394k data, 184k init) Calibrating delay using timer specific routine.. 4006.42 BogoMIPS (lpj=8012858) Security Framework v1.0.0 initialized SELinux: Initializing. selinux_register_security: Registering secondary module capability Capability LSM initialized as secondary Mount-cache hash table entries: 256 CPU: L1 I Cache: 64K (64 bytes/line), D cache 16K (64 bytes/line) CPU: L2 Cache: 2048K (64 bytes/line) general protection fault: 0000 [1] SMP last sysfs file: CPU 0 Modules linked in: Pid: 0, comm: swapper Not tainted 2.6.18-194.0.0.0.3.el5xen #1 RIP: e030:[ffffffff80271280] [ffffffff80271280] identify_cpu+0x210/0x494 RSP: e02b:ffffffff80643f70 EFLAGS: 00010212 RAX: 0040401000810008 RBX: 0000000000000000 RCX: 00000000c001001f RDX: 0000000000404010 RSI: 0000000000000001 RDI: 0000000000000005 RBP: ffffffff8063e980 R08: 0000000000000025 R09: ffff8800019d1000 R10: 0000000000000026 R11: ffff88000102c400 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffffffff805d2000(0000) knlGS:0000000000000000 CS: e033 DS: 0000 ES: 0000 Process swapper (pid: 0, threadinfo ffffffff80642000, task ffffffff804f4b80) Stack: 0000000000000000 ffffffff802d09bb ffffffff804f4b80 0000000000000000 0000000021100800 0000000000000000 0000000000000000 ffffffff8064cb00 0000000000000000 0000000000000000 Call Trace: [ffffffff802d09bb] kmem_cache_zalloc+0x62/0x80 [ffffffff8064cb00] start_kernel+0x210/0x224 [ffffffff8064c1e5] _sinittext+0x1e5/0x1eb Code: 0f 30 b8 73 00 00 00 f0 0f ab 45 08 e9 f0 00 00 00 48 89 ef RIP [ffffffff80271280] identify_cpu+0x210/0x494 RSP ffffffff80643f70 0 Kernel panic - not syncing: Fatal exception clear as mud to me. are there any other logs that will help me? I have now deployed another vm from the same template and used the default vm settings rather than adding more memory etc - I get exactly the same error.

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WinAPI window taking 50% of CPU when idle

- by henryprescott

I'm currently working on a game that creates a window using WindowsAPI. However, at the moment the process is taking up 50% of my CPU. All I am doing is creating the window and looping using the code found below: int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd) { MSG message = {0}; WNDCLASSEX wcl = {0}; wcl.cbSize = sizeof(wcl); wcl.style = CS_OWNDC | CS_HREDRAW | CS_VREDRAW; wcl.lpfnWndProc = WindowProc; wcl.cbClsExtra = 0; wcl.cbWndExtra = 0; wcl.hInstance = hInstance = hInstance; wcl.hIcon = LoadIcon(0, IDI_APPLICATION); wcl.hCursor = LoadCursor(0, IDC_ARROW); wcl.hbrBackground = 0; wcl.lpszMenuName = 0; wcl.lpszClassName = "GL2WindowClass"; wcl.hIconSm = 0; if (!RegisterClassEx(&wcl)) return 0; hWnd = CreateAppWindow(wcl, "Application"); if (hWnd) { if (Init()) { ShowWindow(hWnd, nShowCmd); UpdateWindow(hWnd); while (true) { while (PeekMessage(&message, 0, 0, 0, PM_REMOVE)) { if (message.message == WM_QUIT) break; TranslateMessage(&message); DispatchMessage(&message); } if (message.message == WM_QUIT) break; if (hasFocus) { elapsedTime = GetElapsedTimeInSeconds(); lastEarth += elapsedTime; lastUpdate += elapsedTime; lastFrame += elapsedTime; lastParticle += elapsedTime; if(lastUpdate >= (1.0f / 100.0f)) { Update(lastUpdate); lastUpdate = 0; } if(lastFrame >= (1.0f / 60.0f)) { UpdateFrameRate(lastFrame); lastFrame = 0; Render(); SwapBuffers(hDC); } if(lastEarth >= (1.0f / 10.0f)) { UpdateEarthAnimation(); lastEarth = 0; } if(lastParticle >= (1.0f / 30.0f)) { particleManager->rightBooster->Update(); particleManager->rightBoosterSmoke->Update(); particleManager->leftBooster->Update(); particleManager->leftBoosterSmoke->Update(); particleManager->breakUp->Update(); lastParticle = 0; } } else { WaitMessage(); } } } Cleanup(); UnregisterClass(wcl.lpszClassName, hInstance); } return static_cast<int>(message.wParam); } So even when I am not drawing anything when the window has focus it still takes up 50%. I don't understand how this is taking up so much system resources. Am I doing something wrong? Any help would be much appreciated, thank you!

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High CPU load for 1:30 minutes when mounting ext4-raid partition

- by sirion

I have a raid 5 (software) with 5x2TB drives. I encrypted the raid with cryptsetup and put an ext4-partition on top. In the beginning opening and mounting the raid took less than 10 seconds, now (for a few weeks) mounting alone takes 1:30 minutes and the cpu stays around 93% the whole time: The output of "time sudo mount /dev/mapper/8000 /media/8000" is: real 1m31.952s user 0m0.008s sys 1m25.229s At the same time only one line is added to /var/log/syslog: kernel: [ 2240.921381] EXT4-fs (dm-1): mounted filesystem with ordered data mode. Opts: (null) My Ubuntu-version is "12.04.1 LTS" and no updates are pending. I checked the partition with fsck, but it says that all is ok. The "cryptsetup luksOpen" command only takes a few seconds. I also tried changing the raid-bitmap (as it was suggested in some forum) but it did not change the behaviour. sudo mdadm --grow /dev/md0 -b internal and sudo mdadm --grow /dev/md0 -b none I had the idea that it might be the hardware being slow, but a read test with "sudo hdparm -t /dev/md0" spit out values between 62 and 159 MB/sec: Timing buffered disk reads: 382 MB in 3.00 seconds = 127.14 MB/sec Timing buffered disk reads: 482 MB in 3.02 seconds = 159.62 MB/sec Timing buffered disk reads: 190 MB in 3.03 seconds = 62.65 MB/sec Timing buffered disk reads: 474 MB in 3.02 seconds = 157.12 MB/sec Although I think it is strange that the read rate jumps by more than 100% - could that mean something? The speed test when reading from the mapped (decrypted) device shows similar behavior, although it is of course much slower. "sudo hdparm -t /dev/mapper/8000": Timing buffered disk reads: 56 MB in 3.02 seconds = 18.54 MB/sec Timing buffered disk reads: 122 MB in 3.09 seconds = 39.43 MB/sec Timing buffered disk reads: 134 MB in 3.02 seconds = 44.35 MB/sec The output of a verbose mount "mount -vvv /dev/mapper/8000 /media/8000" does not help much: mount: fstab path: "/etc/fstab" mount: mtab path: "/etc/mtab" mount: lock path: "/etc/mtab~" mount: temp path: "/etc/mtab.tmp" mount: UID: 0 mount: eUID: 0 mount: spec: "/dev/mapper/8000" mount: node: "/media/8000" mount: types: "(null)" mount: opts: "(null)" mount: you didn't specify a filesystem type for /dev/mapper/8000 I will try type ext4 mount: mount(2) syscall: source: "/dev/mapper/8000", target: "/media/8000", filesystemtype: "ext4", mountflags: -1058209792, data: (null) Any idea where I could find additional information on why mounting takes so long, or what additional tests I could run?

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Do programmable Ethernet devices (think onboard CPU) really exist?

- by PeterM

I've heard from various people that programmable Ethernet cards exist and are easily available. However I have yet to be able to track down one of these mythical devices so I'm wondering if they're just that - a myth. Such a programmable card has a gigabit Ethernet interface, has a programmable CPU and connects to the host system via PCI Express. The problem area these cards address are low latency network applications where the card itself does the work and "reports back" to the operating system. Basically the card acts as a co-processor and handles all the low latency requirements on the card, thus avoiding the issues of writing low latency code in user-land - think 0.4ms - 0.5ms response times. So my question is, do these cards really exist and if so, where can I get my hands on one?

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Does a CPU assigns a value atomically to memory?

- by Poni

Hi! A quick question I've been wondering about for some time; Does the CPU assign values atomically, or, is it bit by bit (say for example a 32bit integer). If it's bit by bit, could another thread accessing this exact location get a "part" of the to-be-assigned value? Think of this: I have two threads and one shared "unsigned int" variable (call it "g_uiVal"). Both threads loop. On is printing "g_uiVal" with printf("%u\n", g_uiVal). The second just increase this number. Will the printing thread ever print something that is totally not or part of "g_uiVal"'s value? In code: unsigned int g_uiVal; void thread_writer() { g_uiVal++; } void thread_reader() { while(1) printf("%u\n", g_uiVal); }

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Skewed: a rotating camera in a simple CPU-based voxel raycaster/raytracer

- by voxelizr

TL;DR -- in my first simple software voxel raycaster, I cannot get camera rotations to work, seemingly correct matrices notwithstanding. The result is skewed: like a flat rendering, correctly rotated, however distorted and without depth. (While axis-aligned ie. unrotated, depth and parallax are as expected.) I'm trying to write a simple voxel raycaster as a learning exercise. This is purely CPU based for now until I figure out how things work exactly -- fow now, OpenGL is just (ab)used to blit the generated bitmap to the screen as often as possible. Now I have gotten to the point where a perspective-projection camera can move through the world and I can render (mostly, minus some artifacts that need investigation) perspective-correct 3-dimensional views of the "world", which is basically empty but contains a voxel cube of the Stanford Bunny. So I have a camera that I can move up and down, strafe left and right and "walk forward/backward" -- all axis-aligned so far, no camera rotations. Herein lies my problem. Screenshot #1: correct depth when the camera is still strictly axis-aligned, ie. un-rotated. Now I have for a few days been trying to get rotation to work. The basic logic and theory behind matrices and 3D rotations, in theory, is very clear to me. Yet I have only ever achieved a "2.5 rendering" when the camera rotates... fish-eyey, bit like in Google Streetview: even though I have a volumetric world representation, it seems --no matter what I try-- like I would first create a rendering from the "front view", then rotate that flat rendering according to camera rotation. Needless to say, I'm by now aware that rotating rays is not particularly necessary and error-prone. Still, in my most recent setup, with the most simplified raycast ray-position-and-direction algorithm possible, my rotation still produces the same fish-eyey flat-render-rotated style looks: Screenshot #2: camera "rotated to the right by 39 degrees" -- note how the blue-shaded left-hand side of the cube from screen #2 is not visible in this rotation, yet by now "it really should"! Now of course I'm aware of this: in a simple axis-aligned-no-rotation-setup like I had in the beginning, the ray simply traverses in small steps the positive z-direction, diverging to the left or right and top or bottom only depending on pixel position and projection matrix. As I "rotate the camera to the right or left" -- ie I rotate it around the Y-axis -- those very steps should be simply transformed by the proper rotation matrix, right? So for forward-traversal the Z-step gets a bit smaller the more the cam rotates, offset by an "increase" in the X-step. Yet for the pixel-position-based horizontal+vertical-divergence, increasing fractions of the x-step need to be "added" to the z-step. Somehow, none of my many matrices that I experimented with, nor my experiments with matrix-less hardcoded verbose sin/cos calculations really get this part right. Here's my basic per-ray pre-traversal algorithm -- syntax in Go, but take it as pseudocode: fx and fy: pixel positions x and y rayPos: vec3 for the ray starting position in world-space (calculated as below) rayDir: vec3 for the xyz-steps to be added to rayPos in each step during ray traversal rayStep: a temporary vec3 camPos: vec3 for the camera position in world space camRad: vec3 for camera rotation in radians pmat: typical perspective projection matrix The algorithm / pseudocode: // 1: rayPos is for now "this pixel, as a vector on the view plane in 3d, at The Origin" rayPos.X, rayPos.Y, rayPos.Z = ((fx / width) - 0.5), ((fy / height) - 0.5), 0 // 2: rotate around Y axis depending on cam rotation. No prob since view plane still at Origin 0,0,0 rayPos.MultMat(num.NewDmat4RotationY(camRad.Y)) // 3: a temp vec3. planeDist is -0.15 or some such -- fov-based dist of view plane from eye and also the non-normalized, "in axis-aligned world" traversal step size "forward into the screen" rayStep.X, rayStep.Y, rayStep.Z = 0, 0, planeDist // 4: rotate this too -- 0,zstep should become some meaningful xzstep,xzstep rayStep.MultMat(num.NewDmat4RotationY(CamRad.Y)) // set up direction vector from still-origin-based-ray-position-off-rotated-view-plane plus rotated-zstep-vector rayDir.X, rayDir.Y, rayDir.Z = -rayPos.X - me.rayStep.X, -rayPos.Y, rayPos.Z + rayStep.Z // perspective projection rayDir.Normalize() rayDir.MultMat(pmat) // before traversal, the ray starting position has to be transformed from origin-relative to campos-relative rayPos.Add(camPos) I'm skipping the traversal and sampling parts -- as per screens #1 through #3, those are "basically mostly correct" (though not pretty) -- when axis-aligned / unrotated.

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Win 7 running slowly with low CPU usage and memory

- by guywhoneedsahand

I have a relatively new (under 2 yrs old) windows 7 machine. It has 9GB of RAM, and an i7 core CPU (930 @ 2.8GHz w/ 8 CPUs). After about 8 months since a clean install, I noticed my computer was running slowly. I figure it was fragmentation etc, and I did a complete wipe & clean reinstall. However, my problems are somehow persisting. The computer is running painfully slowly (but in leaps and bounds - sometimes it will work fine for 3 hrs, then suddenly freeze up just from clicking the start button). The 'freezes' happen randomly - not during any especially intensive computing. I initially thought something might be eating through my CPU and/or Memory, but Task Manager indicates that neither the CPU or Memory spike. In fact, even during serious lag, CPU usage remains at less than 5% and Memory at ~ 1.5GB. It's beyond me why a fresh install on a powerful machine is performing so poorly... and it certainly is frustrating! What could be causing the poor performance, and what can I do to fix it?

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High load average, low CPU and IO (Centos 5.7)

- by Ben

A Drupal 7 site with CiviCRM, after running smoothly for a year on a 1&1 VPS suddenly became unresponsive. Now pages eventually load, but can take more than a minute. Looking at resource use in Virtuozzo, the load average carries a warning, and has remained above 1. While I understand this isn't particularly high, this is a change from when the site was working. Here is a typical snapshot of top: top - 03:10:32 up 3:21, 1 user, load average: 1.16, 1.22, 1.30 Tasks: 43 total, 1 running, 42 sleeping, 0 stopped, 0 zombie Cpu(s): 0.1%us, 0.1%sy, 0.1%ni, 99.7%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 2097152k total, 1015112k used, 1082040k free, 0k buffers Swap: 0k total, 0k used, 0k free, 0k cached CPU idle level never seems to go much below 70%. wa is virtually always at 0. There appears to be lots of free memory. And here is some vmstat output, again showign wa at 0, plenty of free memory, and an idle CPU: procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------ r b swpd free buff cache si so bi bo in cs us sy id wa st 2 0 0 1100872 0 0 0 0 2783 23672 0 538 1 0 99 0 0 1 0 0 1100872 0 0 0 0 0 16 0 101754 0 0 100 0 0 0 0 0 1100872 0 0 0 0 0 17 0 103133 0 0 100 0 0 0 0 0 1100872 0 0 0 0 0 1 0 102080 0 0 100 0 0 1 0 0 1100872 0 0 0 0 0 6 0 99881 0 0 100 0 0 0 0 0 1100872 0 0 0 0 0 1 0 105187 0 0 100 0 0 I've spoken to 1&1 but they don't have any ideas as to what could be causing the high load average. Instead they suggested an upgrade :) I've looked for processes that might be causing this, examined MySQL showprocesslist, and restarted the container with no result. Does anyone have more troubleshooting suggestions or insights?

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Virtualbox HTTP load testing, host CPU overload issues

- by aschuler

I'm doing HTTP load testing benchmarks (using Apache Benchmark and Siege) on a small Java EE 1.7.0 / Tomcat 7.0.26 application running on a Debian Squeeze 6.0.4 x64 virtualized with Virtualbox 4.1.8. The computer host is Ubuntu 11.10 x64. I've modified those parameters in the Tomcat server.xml : <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="200000" redirectPort="8443" acceptCount="2000" maxThreads="150" minSpareThreads="50" /> The application executed on the server takes around 300ms. This app is running well until a certain amount of concurrent connections like those one : ab -n 500 -c 150 http://xx.xx.xx.xx:8080/myapp/ ab -n 1000 -c 50 http://xx.xx.xx.xx:8080/myapp/ siege -b -c 100 -r 20 http://xx.xx.xx.xx:8080/myapp/ A lot of socket connection timed out happens and this completly overload the host processor (but the CPU load inside the VM is normal). Doing an htop on the host, i can see that the Virtualbox processus is running under 300% CPU and never come down even after the load test is finished. (I've allocated 4 processors to the VM, if I allocate only one processor, CPU load goes under 100%). Restarting Tomcat don't do anything, i'm forced to restart the whole VM. I've tryed to launch those ab/siege commands locally on the VM and everything goes well. I first thought it was related to a linux network limit as explained here: Running some benchmarks using ab, and tomcat starts to really slow down So I've modified those TCP parameters : echo 15 > /proc/sys/net/ipv4/tcp_fin_timeout echo 30 > /proc/sys/net/ipv4/tcp_keepalive_intvl echo 1 > /proc/sys/net/ipv4/tcp_tw_recycle echo 1 > /proc/sys/net/ipv4/tcp_tw_reuse It seems to be better, but it continues to overload the host CPU and output socket connections time out at a certain amount of concurrent connections. I'm wondering if this is not related to how Virtualbox handles external concurrent connections.

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mysqld causes high CPU load

- by Radu

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OpenVPN Server - CPU is pegged out

- by ericl42

Hello, I am configuring OpenVPN to act as a SSL tunnel for a remote location. I have OpenVPN1 at our current location acting as a server then OpenVPN2 at the other location that is acting as a client but is also acting as a DHCP server to machines behind it so they are basically connected to the local LAN. Everything is set up fine and I can talk from location A to location B with no problems like everyone is local. I am however having some performance issues. OpenVPN1 CPU is pegged to 100% the entire time I am copying or doing any type of activity through the tunnel. I expect some CPU usage going up but nothing like this. It's really killing my performance. OpenVPN1 is running in ESX right now with 2 gig RAM and 4 procs with unlimited bursting capacity. I am using AES-192 encryption with a 1024 key. Any idea how I can get my CPU down on OpenVPN1 and my download/upload speeds higher between the tunnel? Thanks. edit: Turning down the logging helped boost the throughput a little bit, but I am still fairly shy of where I believe I should be. Also I am still maxed out on the CPU. Does anyone have any ideas? I am really stuck on this. Thanks.

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