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• Cherokee high virtual memory usage even after disabling I/O Cache

  - by nidheeshdas

  hi all I've Ubuntu 10.04LTS 64-bit running on a openvz container and Cherokee 1.0.8 compiled from source. The virtual memory usage of cherokee-worker is around 430 MB even after disabling I/O cache from Advanced - I/O Cache - NOT enabled. Is this issue particular to openvz? Because many people reported to have successfully reduced virt memory usage by disabling io cache. htop output: http://imgur.com/z5JEL.jpg (newbies not allowed to post image.) thanks in advance. nidheeshdas

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• iTunes high CPU usage

  - by Calm Storm

  I upgraded to iTunes 10.4.1 and use Windows 7 and my itunes library is not that large at all (say about 20gb) When I start iTunes the CPU goes between 60-80% and stays there for a long time. I see that the itunes.exe takes about 70% of CPU in Process Explorer and it spawns a SearchProtocolHost.exe every 2 mins or so which takes < 0.1% CPU. Other than that iTunes.exe is always at 70-90% and never lets me do anything else. Does someone have a suggestion? EDIT: I have tried reinstalling 10.4.1 completely deleting my library and starting with a plain installation and that does not work I have tried downgrading to 10.3.x and that does not work either :(

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• High IO latency on ESXi 4.1 on HP DL580 G7

  - by teddydestodes

  at my Company we were experiencing some weird spikes on IO latency on one of our ESXi instances. we've spend 24h figuring out whats wrong and no clue so far. after giving up we put all the disks into a different server (HP DL380 G7) with much less RAM and only one 6(HT) cores (from 12 on the DL 580) which run fine for about 2 hours. I dont know the specs for the DL380 but both servers have a Smart Array P410i with BBWC (the DL 580 has 1GB) Is it possible that one(or all) of the disks is failing without actually failing?

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• Poor disk performance with high disk capacity usage

  - by GoldenNewby

  I've heard numerous times in the web hosting industry that using "too much" disk space on a drive is bad for performance. Is this just a myth? Can someone explain why this is an issue, even in a situation where the amount of IO done to the drive would be the same at 10% as it would be at 90%? I'm especially curious in the case of virtual servers. If I set up 10 Logical volumes as the virtual disks for some VMs, is it going to run better if I "waste" 20% of the disk space?

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• Apache 2 settings for high traffic website

  - by Harry

  I'm having problems with the load on my website. It's an amazon ec2 server with 15Gb ram and 4 CPUs behind an LB. apachetop says I'm getting around 80 reqs per second which seems really low for this kind of server and the load ( given by top ) is usually around 15 but does increase to about 150 in 24 hrs. I'm seeing about 100 active apache processes at any time. Apache is in prefork mode. Mysql is used very little on the server and there are almost no static files. Here are my Apache settings: Timeout 20 KeepAlive Off MaxKeepAliveRequests 0 KeepAliveTimeout 3 <IfModule mpm_prefork_module> StartServers 40 MinSpareServers 25 MaxSpareServers 40 ServerLimit 400 MaxClients 400 MaxRequestsPerChild 4 </IfModule> Can anyone advise on how to tweak the settings? Thanx! Edit: The config was gotten by trial and error. Any and I mean by a number, change to these lines make the load skyrocket in like 5 minutes. It literally jumps to like 200-300 in a matter of minutes. Especially MaxRequestsPerChild. I've tried with 10, 15, 100, 1000 and the load just skyrockets. About php - there are actually only a few php files which aren't really that expensive at all. They just spit some simple stuff out. If I turn on KeepAlive load also goes to space..

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• High Availability Clustering and Virtualization

  - by tmcallaghan

  I'm trying to understand how the various virtualization vendors (specifically Amazon EC2, but also VMware and Xen) enable software vendors to provide a real HA solution in the environment where the servers are virtualized. Specifically, if I'm running any HA application (exchange, databases, etc) I need to ensure that my redundant virtual "servers" aren't located on the same physical server. Using in-house virtualization solutions (VMware, Xen, etc) I can provision accordingly as well as check the virtual - physical arrangement. I could, however, accidentally "vmotion" to the same physical hardware. With EC2, I don't even have the ability at provision time to select different physical servers. Since their Cluster Compute Instances are 1 virtual server per physical server it seems to be the only way to guarantee I don't have a false sense of redundancy. Any ideas or thoughts would be helpful. What are others doing about this problem? If the vendors provided an API where I could get something as simple as a unique physical system identifier I could at least know if I'm going to have an issue. -Tim

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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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• Remote Desktop svchost (networkservice) & lsa.exe high cpu usage, hangs on welcome screen

  - by Rohan1

  We have deployed an RDS Farm with 12 virtual RDS servers using Hyper V. Currently some users are not able to log on. After passing credentials to the connection broker, the session hangs on the "Welcome" screen. Using resource monitor we've seen that svchost (with the "networkservice" service) has a CPU usage of 50%, when viewing the wait chain on the process it displays that it's waiting for a lsa.exe to finish. We can't kill any of the users processes, even when trying with taskkill /f. Suspending lsa.exe did work but didn't have any effect. The networkservice also couldn't be restarted. Also, if this happens, the current users logged on to the RDS server can't be displayed. Task manager crashes when viewing the users, RDS service manager crashes when viewing the users (even remotely) and the cmd command "query session" doesn't work. No antivirus is installed on the RDS server. The only thing we can do is rebooting the server, which is not an option because of the fact that other users are in active sessions. Does anyone have ANY idea what's going on? We didn't encounter this in our pre-production setup.

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• Mysql showing some high spikes

  - by user111196

  We one mysql server suddenly the access to it becomes slow of out sudden. So I read some place they said maybe due to var size is it? I am not too sure any idea how to check the root cause of it. The cpu is like nearly 150%. Any indication on it. I have tried this so far. du -sh * 4.0K account 67M cache 4.0K cvs 16K db 8.0K empty 4.0K games 4.0K gdm 148G lib 4.0K local 16K lock 624M log 0 mail 4.0K nis 4.0K opt 4.0K preserve 400K run 298M spool 4.0K tmp 359M www 12K yp

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• How much powerful processor is required while downlaoding data from a high speed internet connection

  - by avanish

  Hello, I was just wondering about the use of a processor while downloading any data (say for example a movie) from internet. Can anyone tell me, how much a processor is really in use while downloading and in first place is a processor really required during download.

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• guvcview recording video and audio out of synchronisation in Ubuntu 10.10

  - by SIJAR

  I finally got Guvcview, a great software for Logitech webcam and it does all the stuff that one wants out of it. But I'm not satisfy with the video recording, video and audio out of synchronisation also video seems to be in slow motion. Please help so that I can tweak in and get a good video recording with the webcam. Below is the log of Guvcview ------------------------------------------------------------------------------- guvcview 1.4.1 video_device: /dev/video0 vid_sleep: 0 cap_meth: 1 resolution: 640 x 480 windowsize: 1024 x 715 vert pane: 578 spin behavior: 0 mode: mjpg fps: 1/25 Display Fps: 0 bpp: 0 hwaccel: 1 avi_format: 4 sound: 1 sound Device: 4 sound samp rate: 0 sound Channels: 0 Sound delay: 0 nanosec Sound Format: 85 Pan Step: 2 degrees Tilt Step: 2 degrees Video Filter Flags: 0 image inc: 0 profile(default):/home/sijar/default.gpfl starting portaudio... bt_audio_service_open: connect() failed: Connection refused (111) bt_audio_service_open: connect() failed: Connection refused (111) bt_audio_service_open: connect() failed: Connection refused (111) bt_audio_service_open: connect() failed: Connection refused (111) Cannot connect to server socket err = No such file or directory Cannot connect to server socket jack server is not running or cannot be started language catalog= dir:/usr/share/locale type:UTF-8 lang:en_US.utf8 cat:guvcview.mo mjpg: setting format to 1196444237 capture method = 1 video device: /dev/video0 libv4lconvert: warning more framesizes then I can handle! libv4lconvert: warning more framesizes then I can handle! /dev/video0 - device 1 libv4lconvert: warning more framesizes then I can handle! libv4lconvert: warning more framesizes then I can handle! Init. UVC Camera (046d:0825) (location: usb-0000:00:1d.7-5) { pixelformat = 'YUYV', description = 'YUV 4:2:2 (YUYV)' } { discrete: width = 640, height = 480 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 160, height = 120 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 176, height = 144 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 320, height = 176 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 320, height = 240 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 352, height = 288 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 432, height = 240 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 544, height = 288 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 640, height = 360 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, ... repeats a couple of times ... vid:046d pid:0825 driver:uvcvideo Adding control for Pan (relative) UVCIOC_CTRL_ADD - Error: Operation not permitted checking format: 1196444237 VIDIOC_G_COMP:: Invalid argument compression control not supported fps is set to 1/25 drawing controls control[0]: 0x980900 Brightness, 0:255:1, default 128 control[0]: 0x980901 Contrast, 0:255:1, default 32 control[0]: 0x980902 Saturation, 0:255:1, default 32 control[0]: 0x98090c White Balance Temperature, Auto, 0:1:1, default 1 control[0]: 0x980913 Gain, 0:255:1, default 0 control[0]: 0x980918 Power Line Frequency, 0:2:1, default 2 control[0]: 0x98091a White Balance Temperature, 0:10000:10, default 4000 control[0]: 0x98091b Sharpness, 0:255:1, default 24 control[0]: 0x98091c Backlight Compensation, 0:1:1, default 1 control[0]: 0x9a0901 Exposure, Auto, 0:3:1, default 3 control[0]: 0x9a0902 Exposure (Absolute), 1:10000:1, default 166 control[0]: 0x9a0903 Exposure, Auto Priority, 0:1:1, default 0 resolutions of format(2) = 19 frame rates of 1º resolution=6 Def. Res: 0 numb. fps:6 --------------------------------------- device #0 Name = Intel 82801DB-ICH4: Intel 82801DB-ICH4 (hw:0,0) Host API = ALSA Max inputs = 2, Max outputs = 2 Def. low input latency = 0.012 Def. low output latency = 0.012 Def. high input latency = 0.046 Def. high output latency = 0.046 Def. sample rate = 44100.00 --------------------------------------- device #1 Name = Intel 82801DB-ICH4: Intel 82801DB-ICH4 - MIC ADC (hw:0,1) Host API = ALSA Max inputs = 2, Max outputs = 0 Def. low input latency = 0.011 Def. low output latency = -1.000 Def. high input latency = 0.043 Def. high output latency = -1.000 Def. sample rate = 48000.00 --------------------------------------- device #2 Name = Intel 82801DB-ICH4: Intel 82801DB-ICH4 - MIC2 ADC (hw:0,2) Host API = ALSA Max inputs = 2, Max outputs = 0 Def. low input latency = 0.011 Def. low output latency = -1.000 Def. high input latency = 0.043 Def. high output latency = -1.000 Def. sample rate = 48000.00 --------------------------------------- device #3 Name = Intel 82801DB-ICH4: Intel 82801DB-ICH4 - ADC2 (hw:0,3) Host API = ALSA Max inputs = 2, Max outputs = 0 Def. low input latency = 0.011 Def. low output latency = -1.000 Def. high input latency = 0.043 Def. high output latency = -1.000 Def. sample rate = 48000.00 --------------------------------------- device #4 Name = Intel 82801DB-ICH4: Intel 82801DB-ICH4 - IEC958 (hw:0,4) Host API = ALSA Max inputs = 0, Max outputs = 2 Def. low input latency = -1.000 Def. low output latency = 0.011 Def. high input latency = -1.000 Def. high output latency = 0.043 Def. sample rate = 48000.00 --------------------------------------- device #5 Name = USB Device 0x46d:0x825: USB Audio (hw:1,0) Host API = ALSA Max inputs = 1, Max outputs = 0 Def. low input latency = 0.011 Def. low output latency = -1.000 Def. high input latency = 0.043 Def. high output latency = -1.000 Def. sample rate = 48000.00 --------------------------------------- device #6 Name = front Host API = ALSA Max inputs = 0, Max outputs = 2 Def. low input latency = -1.000 Def. low output latency = 0.012 Def. high input latency = -1.000 Def. high output latency = 0.046 Def. sample rate = 44100.00 --------------------------------------- device #7 Name = iec958 Host API = ALSA Max inputs = 0, Max outputs = 2 Def. low input latency = -1.000 Def. low output latency = 0.011 Def. high input latency = -1.000 Def. high output latency = 0.043 Def. sample rate = 48000.00 --------------------------------------- device #8 Name = spdif Host API = ALSA Max inputs = 0, Max outputs = 2 Def. low input latency = -1.000 Def. low output latency = 0.011 Def. high input latency = -1.000 Def. high output latency = 0.043 Def. sample rate = 48000.00 --------------------------------------- device #9 Name = pulse Host API = ALSA Max inputs = 32, Max outputs = 32 Def. low input latency = 0.012 Def. low output latency = 0.012 Def. high input latency = 0.046 Def. high output latency = 0.046 Def. sample rate = 44100.00 --------------------------------------- device #10 Name = dmix Host API = ALSA Max inputs = 0, Max outputs = 2 Def. low input latency = -1.000 Def. low output latency = 0.043 Def. high input latency = -1.000 Def. high output latency = 0.043 Def. sample rate = 48000.00 --------------------------------------- device #11 [ Default Input, Default Output ] Name = default Host API = ALSA Max inputs = 32, Max outputs = 32 Def. low input latency = 0.012 Def. low output latency = 0.012 Def. high input latency = 0.046 Def. high output latency = 0.046 Def. sample rate = 44100.00 ---------------------------------------------- SampleRate:0 Channels:0 Video driver: x11 A window manager is available VIDIOC_S_EXT_CTRLS for multiple controls failed (error -1) using VIDIOC_S_CTRL for user class controls control(0x0098091a) "White Balance Temperature" failed to set (error -1) VIDIOC_S_EXT_CTRLS for multiple controls failed (error -1) using VIDIOC_S_EXT_CTRLS on single controls for class: 0x009a0000 control(0x009a0902) "Exposure (Absolute)" failed to set (error -1) VIDIOC_S_EXT_CTRLS for multiple controls failed (error -1) using VIDIOC_S_CTRL for user class controls control(0x0098091a) "White Balance Temperature" failed to set (error -1) VIDIOC_S_EXT_CTRLS for multiple controls failed (error -1) using VIDIOC_S_EXT_CTRLS on single controls for class: 0x009a0000 control(0x009a0902) "Exposure (Absolute)" failed to set (error -1) Cap Video toggled: 1 (/home/sijar/Videos/Webcam) 25371756K bytes free on a total of 39908968K (used: 36 %) treshold=51200K using audio codec: 0x0055 Audio frame size is 1152 samples for selected codec IO thread started...OK [libx264 @ 0x8cbd8b0]using cpu capabilities: MMX2 SSE2 Cache64 [libx264 @ 0x8cbd8b0]profile Baseline, level 3.0 [libx264 @ 0x8cbd8b0]non-strictly-monotonic PTS shift sound by -9 ms shift sound by -9 ms shift sound by -9 ms AUDIO: droping audio data AUDIO: droping audio data AUDIO: droping audio data AUDIO: droping audio data AUDIO: droping audio data ... repeats a couple of times ... AUDIO: droping audio data (/home/sijar/Videos/Webcam) 25371748K bytes free on a total of 39908968K (used: 36 %) treshold=51200K AUDIO: droping audio data AUDIO: droping audio data ... repeats a couple of times ... Cap Video toggled: 0 Shuting Down IO Thread AUDIO: droping audio data stop= 4426644744000 start=4416533023000 VIDEO: 146 frames in 10111.000000 ms = 14.439719 fps Stoping audio stream Closing audio stream... close avi Last message repeated 145 times [libx264 @ 0x8cbd8b0]frame I:2 Avg QP:14.10 size: 24492 [libx264 @ 0x8cbd8b0]frame P:103 Avg QP:16.06 size: 20715 [libx264 @ 0x8cbd8b0]mb I I16..4: 48.4% 0.0% 51.6% [libx264 @ 0x8cbd8b0]mb P I16..4: 57.5% 0.0% 0.0% P16..4: 40.2% 0.0% 0.0% 0.0% 0.0% skip: 2.3% [libx264 @ 0x8cbd8b0]final ratefactor: 62.05 [libx264 @ 0x8cbd8b0]coded y,uvDC,uvAC intra: 79.7% 92.2% 68.4% inter: 62.4% 87.5% 48.0% [libx264 @ 0x8cbd8b0]i16 v,h,dc,p: 23% 17% 41% 19% [libx264 @ 0x8cbd8b0]i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 30% 24% 26% 2% 5% 3% 3% 3% 4% [libx264 @ 0x8cbd8b0]i8c dc,h,v,p: 53% 20% 23% 4% [libx264 @ 0x8cbd8b0]ref P L0: 63.0% 37.0% [libx264 @ 0x8cbd8b0]kb/s:-0.00 total frames encoded: 0 total audio frames encoded: 0 IO thread finished...OK IO Thread finished enabling controls Cap Video toggled: 1 (/home/sijar/Videos/Webcam) 25379744K bytes free on a total of 39908968K (used: 36 %) treshold=51200K using audio codec: 0x0055 Audio frame size is 1152 samples for selected codec IO thread started...OK [libx264 @ 0x8cfba20]using cpu capabilities: MMX2 SSE2 Cache64 [libx264 @ 0x8cfba20]profile Baseline, level 3.0 [libx264 @ 0x8cfba20]non-strictly-monotonic PTS shift sound by -236 ms shift sound by -236 ms shift sound by -236 ms (/home/sijar/Videos/Webcam) 25377044K bytes free on a total of 39908968K (used: 36 %) treshold=51200K (/home/sijar/Videos/Webcam) 25373408K bytes free on a total of 39908968K (used: 36 %) treshold=51200K AUDIO: droping audio data AUDIO: droping audio data AUDIO: droping audio data AUDIO: droping audio data AUDIO: droping audio data AUDIO: droping audio data ... repeats a couple of times ... (/home/sijar/Videos/Webcam) 25370696K bytes free on a total of 39908968K (used: 36 %) treshold=51200K AUDIO: droping audio data AUDIO: droping audio data AUDIO: droping audio data ... repeats a couple of times ... (/home/sijar/Videos/Webcam) 25367680K bytes free on a total of 39908968K (used: 36 %) treshold=51200K (/home/sijar/Videos/Webcam) 25364052K bytes free on a total of 39908968K (used: 36 %) treshold=51200K (/home/sijar/Videos/Webcam) 25360312K bytes free on a total of 39908968K (used: 36 %) treshold=51200K (/home/sijar/Videos/Webcam) 25356628K bytes free on a total of 39908968K (used: 36 %) treshold=51200K (/home/sijar/Videos/Webcam) 25352908K bytes free on a total of 39908968K (used: 36 %) treshold=51200K (/home/sijar/Videos/Webcam) 25349316K bytes free on a total of 39908968K (used: 36 %) treshold=51200K (/home/sijar/Videos/Webcam) 25345552K bytes free on a total of 39908968K (used: 36 %) treshold=51200K (/home/sijar/Videos/Webcam) 25341828K bytes free on a total of 39908968K (used: 36 %) treshold=51200K (/home/sijar/Videos/Webcam) 25338092K bytes free on a total of 39908968K (used: 36 %) treshold=51200K (/home/sijar/Videos/Webcam) 25334412K bytes free on a total of 39908968K (used: 36 %) treshold=51200K Cap Video toggled: 0 Shuting Down IO Thread stop= 4708817235000 start=4578624714000 VIDEO: 1604 frames in 130192.000000 ms = 12.320265 fps Stoping audio stream Closing audio stream... close avi Last message repeated 1603 times [libx264 @ 0x8cfba20]frame I:16 Avg QP:14.78 size: 42627 [libx264 @ 0x8cfba20]frame P:1547 Avg QP:16.44 size: 28599 [libx264 @ 0x8cfba20]mb I I16..4: 21.6% 0.0% 78.4% [libx264 @ 0x8cfba20]mb P I16..4: 28.1% 0.0% 0.0% P16..4: 70.5% 0.0% 0.0% 0.0% 0.0% skip: 1.4% [libx264 @ 0x8cfba20]final ratefactor: 88.17 [libx264 @ 0x8cfba20]coded y,uvDC,uvAC intra: 74.4% 95.8% 83.2% inter: 75.2% 94.6% 69.2% [libx264 @ 0x8cfba20]i16 v,h,dc,p: 27% 17% 40% 16% [libx264 @ 0x8cfba20]i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 25% 25% 21% 3% 6% 4% 5% 4% 7% [libx264 @ 0x8cfba20]i8c dc,h,v,p: 61% 18% 18% 4% [libx264 @ 0x8cfba20]ref P L0: 64.0% 36.0% [libx264 @ 0x8cfba20]kb/s:-0.00 total frames encoded: 0 total audio frames encoded: 0 IO thread finished...OK IO Thread finished enabling controls Shuting Down Thread Thread terminated... cleaning Thread allocations: 100% SDL Quit Video Thread finished write /home/sijar/.guvcviewrc OK free audio mutex closed v4l2 strutures free controls free controls - vidState cleaned allocations - 100% Closing portaudio ...OK Closing GTK... OK

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• High Profile ASP.NET websites

  - by nandos

  About twice a month I get asked to justify the reason "Why are we using ASP.NET and not PHP or Java, or buzz-word-of-the-month-here, etc". 100% of the time the questions come from people that do not understand anything about technology. People that would not know the difference between FTP and HTTP. The best approach I found (so far) to justify it to people without getting into technical details is to just say "XXX website uses it". Which I get back "Oh...I did not know that, so ASP.NET must be good". I know, I know, it hurts. But it works. So, without getting into the merit of why I'm using ASP.NET (which could trigger an endless argument for other platforms), I'm trying to compile a list of high profile websites that are implemented in ASP.NET. (No, they would have no idea what StackOverflow is). Can you name a high-profile website implemented in ASP.NET? EDIT: Current list (thanks for all the responses): (trying to avoid tech sites and prioritizing retail sites) Costco - http://www.costco.com/ Crate & Barrel - http://www.crateandbarrel.com/ Home Shopping Network - http://www.hsn.com/ Buy.com - http://www.buy.com/ Dell - http://www.dell.com Nasdaq - http://www.nasdaq.com/ Virgin - http://www.virgin.com/ 7-Eleven - http://www.7-eleven.com/ Carnival Cruise Lines - http://www.carnival.com/ L'Oreal - http://www.loreal.com/ The White House - http://www.whitehouse.gov/ Remax - http://www.remax.com/ Monster Jobs - http://www.monster.com/ USA Today - http://www.usatoday.com/ ComputerJobs.com - http://computerjobs.com/ Match.com - http://www.match.com National Health Services (UK) - http://www.nhs.uk/ CarrerBuilder.com - http://www.careerbuilder.com/

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• Programming activities for high school kids who have no idea what CS or programming is

  - by pointdxt

  I work at a small high school that's in a very high poverty area. There are only a handful of seniors that are thinking about applying to be an engineer of some sort in college and only 1 kid that applied for Computer Science (he has a couple acceptances so far!). He's been talking to me a lot as I majored in Computer Science as well and he is very excited about it. Unfortunately, our school doesn't have a Computer Science course of any kind so he asks me a lot of stuff. I want to help him out since he's really excited about majoring in CS but I don't know where to begin. I could say put Linux on a computer, go online and go research stuff like I did but this kid needs some direction and he doesn't even know what Linux is let alone have a free computer around for that sort of thing. He doesn't know much about CS but is keenly interested in having a computer do all sorts of things but I don't know how to help him in a meaningful way. Any advice? I'm not a teacher at the school so I'm not a great educator, I do IT at the school.

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• High-concurrency counters without sharding

  - by dound

  This question concerns two implementations of counters which are intended to scale without sharding (with a tradeoff that they might under-count in some situations): http://appengine-cookbook.appspot.com/recipe/high-concurrency-counters-without-sharding/ (the code in the comments) http://blog.notdot.net/2010/04/High-concurrency-counters-without-sharding My questions: With respect to #1: Running memcache.decr() in a deferred, transactional task seems like overkill. If memcache.decr() is done outside the transaction, I think the worst-case is the transaction fails and we miss counting whatever we decremented. Am I overlooking some other problem that could occur by doing this? What are the significiant tradeoffs between the two implementations? Here are the tradeoffs I see: #2 does not require datastore transactions. To get the counter's value, #2 requires a datastore fetch while with #1 typically only needs to do a memcache.get() and memcache.add(). When incrementing a counter, both call memcache.incr(). Periodically, #2 adds a task to the task queue while #1 transactionally performs a datastore get and put. #1 also always performs memcache.add() (to test whether it is time to persist the counter to the datastore). Conclusions (without actually running any performance tests): #1 should typically be faster at retrieving a counter (#1 memcache vs #2 datastore). Though #1 has to perform an extra memcache.add() too. However, #2 should be faster when updating counters (#1 datastore get+put vs #2 enqueue a task). On the other hand, with #1 you have to be a bit more careful with the update interval since the task queue quota is almost 100x smaller than either the datastore or memcahce APIs.

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• Timer a usage in msp430 in high compiler optimization mode

  - by Vishal

  Hi, I have used timer A in MSP430 with high compiler optimization, but found that my timer code is failing when high compiler optimization used. When none optimization is used code works fine. This code is used to achieve 1 ms timer tick. timeOutCNT is increamented in interrupt. Following is the code, //Disable interrupt and clear CCR0 TIMER_A_TACTL = TIMER_A_TASSEL | // set the clock source as SMCLK TIMER_A_ID | // set the divider to 8 TACLR | // clear the timer MC_1; // continuous mode TIMER_A_TACTL &= ~TIMER_A_TAIE; // timer interrupt disabled TIMER_A_TACTL &= 0; // timer interrupt flag disabled CCTL0 = CCIE; // CCR0 interrupt enabled CCR0 = 500; TIMER_A_TACTL &= TIMER_A_TAIE; //enable timer interrupt TIMER_A_TACTL &= TIMER_A_TAIFG; //enable timer interrupt TACTL = TIMER_A_TASSEL + MC_1 + ID_3; // SMCLK, upmode timeOutCNT = 0; //timeOutCNT is increased in timer interrupt while(timeOutCNT <= 1); //delay of 1 milisecond TIMER_A_TACTL = TIMER_A_TASSEL | // set the clock source as SMCLK TIMER_A_ID | // set the divider to 8 TACLR | // clear the timer MC_1; // continuous mode TIMER_A_TACTL &= ~TIMER_A_TAIE; // timer interrupt disabled TIMER_A_TACTL &= 0x00; // timer interrupt flag disabled Can anybody help me here to resolve this issue? Is there any other way we can use timer A so it works fine in optimization modes? Or do I have used is wrongly to achieve 1 ms interrupt? Thanks in advanced. Vishal N

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• iPhone OS: Strategies for high density image work

  - by Jasconius

  I have a project that is coming around the bend this summer that is going to involve, potentially, an extremely high volume of image data for display. We are talking hundreds of 640x480-ish images in a given application session (scaled to a smaller resolution when displayed), and handfuls of very large (1280x1024 or higher) images at a time. I've already done some preliminary work and I've found that the typical 640x480ish image is just a shade under 1MB in memory when placed into a UIImageView and displayed... but the very large images can be a whopping 5+ MB's in some cases. This project is actually be targeted at the iPad, which, in my Instruments tests seems to cap out at about 80-100MB's of addressable physical memory. Details aside, I need to start thinking of how to move huge volumes of image data between virtual and physical memory while preserving the fluidity and responsiveness of the application, which will be high visibility. I'm probably on the higher ends of intermediate at Objective-C... so I am looking for some solid articles and advice on the following: 1) Responsible management of UIImage and UIImageView in the name of conserving physical RAM 2) Merits of using CGImage over UIImage, particularly for the huge images, and if there will be any performance gain 3) Anything dealing with memory paging particularly as it pertains to images I will epilogue by saying that the numbers I have above maybe off by about 10 or 15%. Images may or may not end up being bundled into the actual app itself as opposed to being loaded in from an external server.

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• Collecting high-volume video viewing data

  - by DanK

  I want to add tracking to our Flash-based media player so that we can provide analytics that show what sections of videos are being watched (at the moment, we just register a view when a video starts playing) For example, if a viewer watches the first 30 seconds of a video and then clicks away to something else, we want the data to reflect that. Likewise, if someone watches the first 10 seconds, then scrubs the timeline to the last minute of the video and watches that, we want to register viewing on the parts watched and not the middle section. My first thought was to collect up the viewing data in the player and send it all to the server at the end of a viewing session. Unfortunately, Flash does not seem to have an event that you can hook into when a viewer clicks away from the page the movie is on (probably a good thing - it would be open to abuse) So, it looks like we're going to have to make regular requests to the server as the video is playing. This is obviously going to lead to a high volume of requests when there are large numbers of simultaneous viewers. The simple approach of dumping all these 'heartbeat' events from clients to a database feels like it will quickly become unmanageable so I'm wondering whether I should be taking an approach where viewing sessions are cached in memory and flushed to database when they become inactive (based on a timeout). That way, the data could be stored as time spans rather than individual heartbeats. So, to the question - what is the best way to approach dealing with this kind of high-volume viewing data? Are there any good existing architectures/patterns? Thanks, Dan.

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• High memory usage for dummies

  - by zaf

  I've just restarted my firefox web browser again because it started stuttering and slowing down. This happens every other day due to (my understanding) of excessive memory usage. I've noticed it takes 40M when it starts and then, by the time I notice slow down, it goes to 1G and my machine has nothing more to offer unless I close other applications. I'm trying to understand the technical reasons behind why its such a difficult problem to sol ve. Mozilla have a page about high memory usage: http://support.mozilla.com/en-US/kb/High+memory+usage But I'm looking for a slightly more in depth and satisfying explanation. Not super technical but enough to give the issue more respect and please the crowd here. Some questions I'm already pondering (they could be silly so take it easy): When I close all tabs, why doesn't the memory usage go all the way down? Why is there no limits on extensions/themes/plugins memory usage? Why does the memory usage increase if it's left open for long periods of time? Why are memory leaks so difficult to find and fix? App and language agnostic answers also much appreciated.

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• Best way to display a "High Scores" Results

  - by George

  First, I would to thank everyone for all the help they provide via this website. It has gotten me to the point of almost being able to release my first iPhone app! Okay, so the last part I have is this: I have a game that allows users to save their high scores. I update a plist file which contains the users Name, Level, and score. Now I want to create a screen that will display the top 20 high scores. What would be the best way to do this? At first I thought possibly creating an HTML file with this info but am not even sure if that is possible. I would need to read the plist file, and then write it out as HTML. Is this possible? To write a file out as HTML? Or an even better question, is there a better way? Thanks in advance for any and all help! Geo...

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• Moving a high quality line on a panel c#

  - by user1787601

  I want to draw a line on a panel and then move it as the mouse moves. To do so, I draw the line and when the mouse moves I redraw the line to the new location and remove the previous line by drawing a line with the background color on it. It works fine if I do not use the high quality smoothing mode. But if use high quality smoothing mode, it leave traces on the panel. Does anybody know how to fix this? Thank you. Here is the code int x_previous = 0; int y_previous = 0; private void panel1_MouseMove(object sender, MouseEventArgs e) { Pen pen1 = new System.Drawing.Pen(Color.Black, 3); Pen pen2 = new System.Drawing.Pen(panel1.BackColor, 3); Graphics g = panel1.CreateGraphics(); g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; g.DrawLine(pen2, new Point(0, 0), new Point(x_previous, y_previous)); g.DrawLine(pen1, new Point(0, 0), new Point(e.Location.X, e.Location.Y)); x_previous = e.Location.X; y_previous = e.Location.Y; } Here is the snapshot with SmoothingMode Here is the snapshot without SmoothingMode

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• Multimaster Keepalived Configuration (Virtual IP with Load Balancing)

  - by Rad Akefirad

  Here are requirements: 1. High Availability 2. Load Balancing First configuration 1. Two linux servers have been configured with one static IP for each: 10.17.243.11, 10.17.243.12 2. Keepalived has been installed and configured with one VRRP instance to provide one virtual IP (10.17.243.10 as VIP, 10.17.243.11 as master and 10.17.243.12 as backup). 3. Everything works fine. The VIP is assigned to the master server (10.17.243.11) as long as it is up and running. As soon as it goes down, the VIP will be assigned to the backup server (10.17.243.12). 4. The problem here is all communication goes to the master server. Second configuration 1. I found active-active configuration for Keepalived which is possible by defining more than one VRRP instance. So that both server have two IPs (real 10.17.243.11 and virtual 10.17.243.10 for server #1 and real 10.17.243.12 and virtual 10.17.243.20 for server #2. 2. Everything works fine. we have two VIPs which are accessible (HA). But all communication coming to each IP still goes to one single machine (either server #1 or #2 depending on the IP). However I found some tricks on the DNS to overcome this limitation. But it's not acceptable in our case. Question: Is there any way to have one virtual IP which is assigned to both servers? By that I mean both servers are handling some part of workload (like the thing we do in web server load balancing)? By using either keepalived or some other tools? Thanks in advance.

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• Keepalived for more than 20 virtual addresses

  - by cvaldemar

  I have set up keepalived on two Debian machines for high availability, but I've run into the maximum number of virtual IP's I can assign to my vrrp_instance. How would I go about configuring and failing over 20+ virtual IP's? This is the, very simple, setup: LB01: 10.200.85.1 LB02: 10.200.85.2 Virtual IPs: 10.200.85.100 - 10.200.85.200 Each machine is also running Apache (later Nginx) binding on the virtual IPs for SSL client certificate termination and proxying to backend webservers. The reason I need so many VIP's is the inability to use VirtualHost on HTTPS. This is my keepalived.conf: vrrp_script chk_apache2 { script "killall -0 apache2" interval 2 weight 2 } vrrp_instance VI_1 { interface eth0 state MASTER virtual_router_id 51 priority 101 virtual_ipaddress { 10.200.85.100 . . all the way to . 10.200.85.200 } An identical configuration is on the BACKUP machine, and it's working fine, but only up to the 20th IP. I have found a HOWTO discussing this problem. Basically, they suggest having just one VIP and routing all traffic "via" this one IP, and "all will be well". Is this a good approach? I'm running pfSense firewalls in front of the machines. Quote from the above link: ip route add $VNET/N via $VIP or route add $VNET netmask w.x.y.z gw $VIP Thanks in advance. EDIT: @David Schwartz said it would make sense to add a route, so I tried adding a static route to the pfSense firewall, but that didn't work as I expected it would. pfSense route: Interface: LAN Destination network: 10.200.85.200/32 (virtual IP) Gateway: 10.200.85.100 (floating virtual IP) Description: Route to VIP .100 I also made sure I had packet forwarding enabled on my hosts: $ cat /etc/sysctl.conf net.ipv4.ip_forward=1 net.ipv4.ip_nonlocal_bind=1 Am I doing this wrong? I also removed all VIPs from the keepalived.conf so it only fails over 10.200.85.100.

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• How should I perform database maintenance on a 24x7 system

  - by solublefish

  I'm a software developer who inherited a part-time DBA role. I'm responsible for an application backed by a small, high-volume 24x7 database on SQL Server 2008. While there's other stuff in the DB, the critical piece is a 50GB, 7.5M row table that serves 100K requests/sec during peak load, and about half that at "night". This is 99%+ read traffic, but the writes are constant, and required. I need to be able to perform periodic maintenance without a maintenance window. Say an index rebuild, a job to purge old data, Windows Update, or hardware upgrade. Most of the advice I've seen is along the lines of "MAKE a maintenance window." While I appreciate the sentiment, I hope there's another way. If it will solve this problem, I do have the ability to purchase new hardware or modify the database, the clients (a set of web services servers), and much of the application code (ADO.NET + ASP.NET). I've been thinking along the lines of using the warm spare (or a 3rd server) to do the maintenance, and then "swap" it into production. 1 Synchronize the spare by restoring backups, including a current transaction log. 2 Perform the maintenance tasks. 3 Reconfigure clients to connect to the spare server. Existing connections are finished within a minute or so. 4 The spare server is now the production server. The problem remaining is that the new production server is now out of date by however long it took to perform maintenance. Is there some way that the original production server can be made to queue up changes and merge them to the spare between steps 2 and 3? Any other ideas?

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• 100% CPU load on Ubuntu 10.04.3 LTS 64bit

  - by deadtired

  I have 2 days since I am trying to fix this issue, with no success. The server is a mysql database server. Hardware: DELL Poweredge 1950, 2x Intel Xeon Quad Core E5345 @ 2.33GHz, 16 Gb mem, 2x 146Gb SAS (software RAID1) Software: Ubuntu 10.04.3 LTS, MySQL 5.1.41 Issue: while mysql is not used and runs with no database, everything seems alright. As soon as I install a database, it has the reason to bring all 8 cores in 100% with low memory consumption. So, you can imagine the load average goes high (I saw 212 load average for the first time). The server doesn't become unresponsive, but you can see it's slow while browsing the project installed. Additional info: the database used is not more than 24MB and it was moved from a server with less resources and a lot more larger databases. So it's not the database/project. my.cnf is not a reason also, as I used both default one and the one I use on the same distribution on another server.What is interesting is that mysql doesn't close any process and runs to the limit of the max_connections. Logs are quiet. Nothing there. I switched to this Ubuntu version after I suspected some problems in the newly Ubuntu 11.10 server. This one worked alright for an hour after I made a kernel upgrade to 3.0.1 (it was using the memory also) I tested disk speed and seems alright. Some more output on the running server: dstat -cndymlp -N total -D total 3: htop command: Idea? Did anyone meet the same problem? Any fix you can think of?

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• Tips / techniques for high-performance C# server sockets

  - by McKenzieG1

  I have a .NET 2.0 server that seems to be running into scaling problems, probably due to poor design of the socket-handling code, and I am looking for guidance on how I might redesign it to improve performance. Usage scenario: 50 - 150 clients, high rate (up to 100s / second) of small messages (10s of bytes each) to / from each client. Client connections are long-lived - typically hours. (The server is part of a trading system. The client messages are aggregated into groups to send to an exchange over a smaller number of 'outbound' socket connections, and acknowledgment messages are sent back to the clients as each group is processed by the exchange.) OS is Windows Server 2003, hardware is 2 x 4-core X5355. Current client socket design: A TcpListener spawns a thread to read each client socket as clients connect. The threads block on Socket.Receive, parsing incoming messages and inserting them into a set of queues for processing by the core server logic. Acknowledgment messages are sent back out over the client sockets using async Socket.BeginSend calls from the threads that talk to the exchange side. Observed problems: As the client count has grown (now 60-70), we have started to see intermittent delays of up to 100s of milliseconds while sending and receiving data to/from the clients. (We log timestamps for each acknowledgment message, and we can see occasional long gaps in the timestamp sequence for bunches of acks from the same group that normally go out in a few ms total.) Overall system CPU usage is low (< 10%), there is plenty of free RAM, and the core logic and the outbound (exchange-facing) side are performing fine, so the problem seems to be isolated to the client-facing socket code. There is ample network bandwidth between the server and clients (gigabit LAN), and we have ruled out network or hardware-layer problems. Any suggestions or pointers to useful resources would be greatly appreciated. If anyone has any diagnostic or debugging tips for figuring out exactly what is going wrong, those would be great as well. Note: I have the MSDN Magazine article Winsock: Get Closer to the Wire with High-Performance Sockets in .NET, and I have glanced at the Kodart "XF.Server" component - it looks sketchy at best.

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