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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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• Appcache and jquery mobile on a CMS powered site?

  - by user793011

  Has anyone used the cache manifest to make a CMS site work offline? I've made a demo with static html files which seems to work fine, so I'm assuming it wouldn't be too hard to achieve the same thing with a CMS. The way that you tell browsers that files have changed (and so need to be downloaded again) is by adding a comment to the cache manifest file so its byte size changes. I'm not quite sure how to do this with a CMS, but maybe some sort of server cron could run periodically? Personally I'm more interested in having a site that works offline rather than achieving ideal performance, so if the file was modified every hour rather than when content actually changed that would be fine for me. If anyone has used appcache with a CMS, has anyone done so with jquery mobile at the same time? What I'm after is a fully native feel to a site that's accessible offline, in other words I want to mimic a native App. My static demo does this perfectly with jquery mobile, so again I would have thought this would be achievable in a CMS.

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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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• CPU Utilization LAMP stack

  - by Max

  We've got an ec2 m2.4xlarge running Magento (centos 5.6, httpd 2.2, php 5.2.17 with eaccelerator 0.9.5.3, mysql 5.1.52). Right now we're getting a large traffic spike, and our top looks like this: top - 09:41:29 up 31 days, 1:12, 1 user, load average: 120.01, 129.03, 113.23 Tasks: 1190 total, 18 running, 1172 sleeping, 0 stopped, 0 zombie Cpu(s): 97.3%us, 1.8%sy, 0.0%ni, 0.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.4%st Mem: 71687720k total, 36898928k used, 34788792k free, 49692k buffers Swap: 880737784k total, 0k used, 880737784k free, 1586524k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 2433 mysql 15 0 23.6g 4.5g 7112 S 564.7 6.6 33607:34 mysqld 24046 apache 16 0 411m 65m 28m S 26.4 0.1 0:09.05 httpd 24360 apache 15 0 410m 60m 25m S 26.4 0.1 0:03.65 httpd 24993 apache 16 0 410m 57m 21m S 26.1 0.1 0:01.41 httpd 24838 apache 16 0 428m 74m 20m S 24.8 0.1 0:02.37 httpd 24359 apache 16 0 411m 62m 26m R 22.3 0.1 0:08.12 httpd 23850 apache 15 0 411m 64m 27m S 16.8 0.1 0:14.54 httpd 25229 apache 16 0 404m 46m 17m R 10.2 0.1 0:00.71 httpd 14594 apache 15 0 404m 63m 34m S 8.4 0.1 1:10.26 httpd 24955 apache 16 0 404m 50m 21m R 8.4 0.1 0:01.66 httpd 24313 apache 16 0 399m 46m 22m R 8.1 0.1 0:02.30 httpd 25119 apache 16 0 411m 59m 23m S 6.8 0.1 0:01.45 httpd Questions: Would giving msyqld more memory help it cache queries and react faster? If so, how? Other than splitting mysql and php to separate servers (which we're about to do) is there anything else we could/should be doing? Thanks! UPDATE: Here's our my.cnf along with the output of mysqltuner. It looks like a cache problem. Thanks again! # cat /etc/my.cnf [client] port = **** socket = /var/lib/mysql/mysql.sock [mysqld] datadir=/mnt/persistent/mysql port=**** socket=/var/lib/mysql/mysql.sock key_buffer = 512M max_allowed_packet = 64M table_cache = 1024 sort_buffer_size = 8M read_buffer_size = 4M read_rnd_buffer_size = 2M myisam_sort_buffer_size = 64M thread_cache_size = 128M tmp_table_size = 128M join_buffer_size = 1M query_cache_limit = 2M query_cache_size= 64M query_cache_type = 1 max_connections = 1000 thread_stack = 128K thread_concurrency = 48 log-bin=mysql-bin server-id = 1 wait_timeout = 300 innodb_data_home_dir = /mnt/persistent/mysql/ innodb_data_file_path = ibdata1:10M:autoextend innodb_buffer_pool_size = 20G innodb_additional_mem_pool_size = 20M innodb_log_file_size = 64M innodb_log_buffer_size = 8M innodb_flush_log_at_trx_commit = 1 innodb_lock_wait_timeout = 50 innodb_thread_concurrency = 48 ft_min_word_len=3 [myisamchk] ft_min_word_len=3 key_buffer = 128M sort_buffer_size = 128M read_buffer = 2M write_buffer = 2M # ./mysqltuner.pl >> MySQLTuner 1.2.0 - Major Hayden <[email protected]> >> Bug reports, feature requests, and downloads at http://mysqltuner.com/ >> Run with '--help' for additional options and output filtering -------- General Statistics -------------------------------------------------- [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 5.1.52-log [OK] Operating on 64-bit architecture -------- Storage Engine Statistics ------------------------------------------- [--] Status: +Archive -BDB +Federated +InnoDB -ISAM -NDBCluster [--] Data in MyISAM tables: 2G (Tables: 26) [--] Data in InnoDB tables: 749M (Tables: 250) [!!] Total fragmented tables: 262 -------- Security Recommendations ------------------------------------------- -------- Performance Metrics ------------------------------------------------- [--] Up for: 31d 2h 30m 38s (680M q [253.371 qps], 2M conn, TX: 4825B, RX: 236B) [--] Reads / Writes: 89% / 11% [--] Total buffers: 20.6G global + 15.1M per thread (1000 max threads) [OK] Maximum possible memory usage: 35.4G (51% of installed RAM) [OK] Slow queries: 0% (35K/680M) [OK] Highest usage of available connections: 53% (537/1000) [OK] Key buffer size / total MyISAM indexes: 512.0M/457.2M [OK] Key buffer hit rate: 100.0% (9B cached / 264K reads) [OK] Query cache efficiency: 42.3% (260M cached / 615M selects) [!!] Query cache prunes per day: 4384652 [OK] Sorts requiring temporary tables: 0% (1K temp sorts / 38M sorts) [!!] Joins performed without indexes: 100404 [OK] Temporary tables created on disk: 17% (7M on disk / 45M total) [OK] Thread cache hit rate: 99% (537 created / 2M connections) [!!] Table cache hit rate: 0% (1K open / 946K opened) [OK] Open file limit used: 9% (453/5K) [OK] Table locks acquired immediately: 99% (758M immediate / 758M locks) [OK] InnoDB data size / buffer pool: 749.3M/20.0G -------- Recommendations ----------------------------------------------------- General recommendations: Run OPTIMIZE TABLE to defragment tables for better performance Enable the slow query log to troubleshoot bad queries Adjust your join queries to always utilize indexes Increase table_cache gradually to avoid file descriptor limits Variables to adjust: query_cache_size (> 64M) join_buffer_size (> 1.0M, or always use indexes with joins) table_cache (> 1024)

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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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• LRU cache design

  - by user297850

  Least Recently Used (LRU) Cache is to discard the least recently used items first How do you design and implement such a cache class? The design requirements are as follows: 1) find the item as fast as we can 2) Once a cache misses and a cache is full, we need to replace the least recently used item as fast as possible. How to analyze and implement this question in terms of design pattern and algorithm design?

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• Cache aspx page returning an asset on client?

  - by Lieven Cardoen

  How do you cache an aspx page call on the client? The aspx page returns an asset and looks like this: http://srv-edu-build/edumatic3/dev/RetrieveBlob.aspx?assetId=31809&assetFileId=9823 We have tried with Output Cache, with caching in the code behind, but the only result we get is server side caching (by IIS7). In the header of the response cache-control is set to public and expiration time is set (to 14800 as set in output cache profile).

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• How can I limit the cache used by copying so there is still memory available for other cache?

  - by Peter

  Basic situation: I am copying some NTFS disks in openSuSE. Each one is 2TB. When I do this, the system runs slow. My guesses: I believe it is likely due to caching. Linux decides to discard useful cache (eg. kde4 bloat, virtual machine disks, LibreOffice binaries, Thunderbird binaries, etc.) and instead fill all available memory (24 GB total) with stuff from the copying disks, which will be read only once, then written and never used again. So then any time I use these apps (or kde4), the disk needs to be read again, and reading the bloat off the disk again makes things freeze/hiccup. Due to the cache being gone and the fact that these bloated applications need lots of cache, this makes the system horribly slow. Since it is USB,the disk and disk controller are not the bottleneck, so using ionice does not make it faster. I believe it is the cache rather than just the motherboard going too slow, because if I stop everything copying, it still runs choppy for a while until it recaches everything. And if I restart the copying, it takes a minute before it is choppy again. But also, I can limit it to around 40 MB/s, and it runs faster again (not because it has the right things cached, but because the motherboard busses have lots of extra bandwidth for the system disks). I can fully accept a performance loss from my motherboard's IO capability being completely consumed (which is 100% used, meaning 0% wasted power which makes me happy), but I can't accept that this caching mechanism performs so terribly in this specific use case. # free total used free shared buffers cached Mem: 24731556 24531876 199680 0 8834056 12998916 -/+ buffers/cache: 2698904 22032652 Swap: 4194300 24764 4169536 I also tried the same thing on Ubuntu, which causes a total system hang instead. ;) And to clarify, I am not asking how to leave memory free for the "system", but for "cache". I know that cache memory is automatically given back to the system when needed, but my problem is that it is not reserved for caching of specific things. Question: Is there some way to tell these copy operations to limit memory usage so some important things remain cached, and therefore any slowdowns are a result of normal disk usage and not rereading the same commonly used files? For example, is there a setting of max memory per process/user/file system allowed to be used as cache/buffers?

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• Can I disable FF3 back button cache?

  - by Sergej Andrejev

  I found out that when pressing back button it gets previous page from browser cache even if I send following headers: Test1.aspx Server ASP.NET Development Server/9.0.0.0 Date Wed, 24 Mar 2010 17:49:40 GMT X-AspNet-Version 2.0.50727 Location Test2.aspx Cache-Control no-cache, no-store Pragma no-cache Expires -1 Content-Type text/html; charset=utf-8 Content-Length 189 Connection Close

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• Cache JSP based on URL parameter

  - by Satheesh

  I have a jsp file pageshow.jsp and the parameter id, Is there any way to cache the jsp file in server-side based on the url parameter Requesting page pageshow.jsp?id=100 get from cache instead of building from server Requesting page pageshow.jsp?id=200 get from cache instead of building from server Above two pages should have different cache content since their parameter are different This may avoid the rebuilding the jsp file in server side and also decrease the server load

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• Hibernate query cache automatically refreshed on external update?

  - by artgon

  I'm creating a service that has read-only access to the database. I have a query cache and a second level cache enabled (READ_ONLY mode) in Hibernate to speed up the service, as the tables being accessed change rarely. My question is, if someone goes into the DB and changes the tables manually (i.e. outside of Hibernate), does the cache recognize automatically that it needs to be cleared? Is there a time limit on the cache?

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• Clear Absolute Cache on Application close Ipad app

  - by geeth

  I am saving Images in NSCachesDirectory in a App. At the end of app execution i would like to clear all temporary cache. Is there a way to force clear all cache on application exit. I do realise the local folder keeps cache for 3 days..but my requirement is to force clear the Cache. Thx

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• How to cache and store objects and set an expire policy in android?

  - by virsir

  I have an app fetch data from internet, for better performance and bandwidth, I need to implement a cache layer. There are two different data coming from the internet, one is changing every one hour and another one does not change basically. So for the first type of data, I need to implement an expire policy to make it self deleted after it was created for 1 hour, and when user request that data, I will check the storage first and then goto internet if nothing found. I thought about using a SharedPrefrence or SQLDatabase to store the json data or serialized object string. My question is: 1) What should I use, SharedPrefrence or SQLDatabase or anything else, a piece of data is not big but there are maybe many instances of that data. 2) How to implement that expire system.

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• using arrays to get best memory alignment and cache use, is it necessary?

  - by Alberto Toglia

  I'm all about performance these days cause I'm developing my first game engine. I'm no c++ expert but after some research I discovered the importance of the cache and the memory alignment. Basically what I found is that it is recommended to have memory well aligned specially if you need to access them together, for example in a loop. Now, In my project I'm doing my Game Object Manager, and I was thinking to have an array of GameObjects references. meaning I would have the actual memory of my objects one after the other. static const size_t MaxNumberGameObjects = 20; GameObject mGameObjects[MaxNumberGameObjects]; But, as I will be having a list of components per object -Component based design- (Mesh, RigidBody, Transformation, etc), will I be gaining something with the array at all? Anyway, I have seen some people just using a simple std::map for storing game objects. So what do you guys think? Am I better off using a pure component model?

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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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• tproxy squid bridge very slow when cache is full

  - by Roberto

  I have installed a bridge tproxy proxy in a fast server with 8GB ram. The traffic is around 60Mb/s. When I start for first time the proxy (with the cache empty) the proxy works very well but when the cache becomes full (few hours later) the bridge goes very slow, the traffic goes below 10Mb/s and the proxy server becomes unusable. Any hints of what may be happening? I'm using: linux-2.6.30.10 iptables-1.4.3.2 squid-3.1.1 compiled with these options: ./configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --datadir=/usr/share --localstatedir=/var/lib --sysconfdir=/etc/squid --libexecdir=/usr/libexec/squid --localstatedir=/var --datadir=/usr/share/squid --enable-removal-policies=lru,heap --enable-icmp --disable-ident-lookups --enable-cache-digests --enable-delay-pools --enable-arp-acl --with-pthreads --with-large-files --enable-htcp --enable-carp --enable-follow-x-forwarded-for --enable-snmp --enable-ssl --enable-async-io=32 --enable-linux-netfilter --enable-epoll --disable-poll --with-maxfd=16384 --enable-err-languages=Spanish --enable-default-err-language=Spanish My squid.conf: cache_mem 100 MB memory_pools off acl manager proto cache_object acl localhost src 127.0.0.1/32 acl localhost src ::1/128 acl to_localhost dst 127.0.0.0/8 0.0.0.0/32 acl to_localhost dst ::1/128 acl localnet src 10.0.0.0/8 # RFC1918 possible internal network acl localnet src 172.16.0.0/12 # RFC1918 possible internal network acl localnet src 192.168.0.0/16 # RFC1918 possible internal network acl localnet src fc00::/7 # RFC 4193 local private network range acl localnet src fe80::/10 # RFC 4291 link-local (directly plugged) machines acl net-g1 src xxx.xxx.xxx.xxx/24 acl SSL_ports port 443 acl Safe_ports port 80 # http acl Safe_ports port 21 # ftp acl Safe_ports port 443 # https acl Safe_ports port 70 # gopher acl Safe_ports port 210 # wais acl Safe_ports port 1025-65535 # unregistered ports acl Safe_ports port 280 # http-mgmt acl Safe_ports port 488 # gss-http acl Safe_ports port 591 # filemaker acl Safe_ports port 777 # multiling http acl CONNECT method CONNECT http_access allow manager localhost http_access deny manager http_access deny !Safe_ports http_access deny CONNECT !SSL_ports http_access allow net-g1 from where browsing should be allowed http_access allow localnet http_access allow localhost http_access deny all http_port 3128 http_port 3129 tproxy hierarchy_stoplist cgi-bin ? cache_dir ufs /var/spool/squid 8000 16 256 access_log none cache_log /var/log/squid/cache.log coredump_dir /var/spool/squid refresh_pattern ^ftp: 1440 20% 10080 refresh_pattern ^gopher: 1440 0% 1440 refresh_pattern -i (/cgi-bin/|\?) 0 0% 0 refresh_pattern . I have this issue when the cache is full, but do not really know if it is because of that. Thanks in advance and sorry my english. roberto

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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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• ASP.Net: Expiring a page when navigating back

  - by K2so

  Basically all pages on this site I am building cannot be accessed when the user clicks on "Back" (or with key control) in the browser, and the page should expire if one is trying to navigate back in history. I put into Global.asax::Application_BeginRequest Response.Cache.SetCacheability(HttpCacheability.NoCache) Response.Cache.SetExpires(DateTime.UtcNow.AddDays(-1)) Response.Cache.SetValidUntilExpires(False) Response.Cache.SetRevalidation(HttpCacheRevalidation.AllCaches) Response.Cache.SetNoStore() This would clear out the cache and disallow going back to any pages when the user is logged out, but doesn't do the job while the user is logged in. I saw posts where people suggested using a javascript approach, by calling History.Forward(1) on the page. But I wouldn't like to do this, as it will require javascript enabled to work (which user can disable). Appreciate any suggestions.

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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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