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  • mongodb : Can create new thread on FreeBSD?

    - by user197739
    We experienced some strange thing in our mongodb gridfs platform. The platform actually is a bi Xeon E5 (bi quad core) with 128GB of memory, running on freebsd 9 with a zfs pool dedicated for mongodb. [root@mongofile1 ~]# uname -sr FreeBSD 9.1-RELEASE our /boot/loader.conf vfs.zfs.arc_min="2048M" vfs.zfs.arc_max="7680M" vm.kmem_size_max="16G" vm.kmem_size="12G" vfs.zfs.prefetch_disable="1" kern.ipc.nmbclusters="32768" /etc/sysctl.conf net.inet.tcp.msl=15000 net.inet.tcp.keepidle=300000 kern.ipc.nmbclusters=32768 kern.ipc.maxsockbuf=2097152 kern.ipc.somaxconn=8192 kern.maxfiles=65536 kern.maxfilesperproc=32768 net.inet.tcp.delayed_ack=0 net.inet.tcp.sendspace=65535 net.inet.udp.recvspace=65535 net.inet.udp.maxdgram=57344 net.local.stream.recvspace=65535 net.local.stream.sendspace=65535 we follow the recommendation for the ulimit : [root@mongofile1 ~]# su - mongodb $ ulimit -a cpu time (seconds, -t) unlimited file size (512-blocks, -f) unlimited data seg size (kbytes, -d) 33554432 stack size (kbytes, -s) 524288 core file size (512-blocks, -c) unlimited max memory size (kbytes, -m) unlimited locked memory (kbytes, -l) unlimited max user processes (-u) 5547 open files (-n) 32768 virtual mem size (kbytes, -v) unlimited swap limit (kbytes, -w) unlimited sbsize (bytes, -b) unlimited pseudo-terminals (-p) unlimited This server have a twin (same config exactly) for ReplSet in other data center and we have a virtualized arbiter. Some time, almost 3 days, the process of mongodb exit. The problem begin with: Fri Nov 8 11:27:31.741 [conn774697] end connection 192.168.10.162:47963 (23 connections now open) Fri Nov 8 11:27:31.770 [initandlisten] can't create new thread, closing connection Fri Nov 8 11:27:31.771 [rsHealthPoll] replSet member mongofile2:27017 is now in state DOWN Fri Nov 8 11:27:31.774 [initandlisten] connection accepted from 192.168.10.162:47968 #774702 (20 connections now open) Fri Nov 8 11:27:31.774 [initandlisten] connection accepted from 192.168.10.161:28522 #774703 (21 connections now open) Fri Nov 8 11:27:31.774 [initandlisten] connection accepted from 192.168.10.164:15406 #774704 (22 connections now open) Fri Nov 8 11:27:31.774 [initandlisten] connection accepted from 192.168.10.163:25750 #774705 (23 connections now open) Fri Nov 8 11:27:31.810 [initandlisten] connection accepted from 192.168.10.182:20779 #774706 (24 connections now open) Fri Nov 8 11:27:31.855 [initandlisten] connection accepted from 192.168.10.161:28524 #774707 (25 connections now open) Fri Nov 8 11:27:31.869 [initandlisten] connection accepted from 192.168.10.182:20786 #774708 (26 connections now open) and after many "can create new thread" [root@mongofile1 /usr/mongodb]# tail -n 15000 mongod.log.old |grep "create new thread"|wc 5020 55220 421680 and finish by a magnificent Fri Nov 8 11:30:22.333 [rsMgr] replSet warning caught unexpected exception in electSelf() pure virtual method called Fri Nov 8 11:30:22.333 Got signal: 6 (Abort trap: 6). Fri Nov 8 11:30:22.337 Backtrace: 0x599efc 0x8035cb516 0x599efc <_ZN5mongo10abruptQuitEi+988> at /usr/local/bin/mongod 0x8035cb516 <_pthread_sigmask+918> at /lib/libthr.so.3 Extract of mongodb from top 78126 mongodb 77 20 0 1253G 1449M sbwait 0 0:20 0.00% mongod If I restart the process when it crash, the problem is fixed for almost 3 days. Has anyone seen this before, or know of a fix?

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  • apache and ajp performance

    - by user12145
    I have an apache sitting in front of two tomcat app servers(one on the same physical server, the other on a different one) that does time consuming work(0.5 sec to 10sec per request). The apache http server is getting killed by an average of 1 to 2 concurrent requests per second. both Server spec is about 2GB of RAM. Is there a way to optimize apache to handle the load? any advise is welcome. BalancerMember ajp://localhost:8009/xxxxxx BalancerMember ajp://XXX.XX.XXX.XX:8009/xxxxxx I keep getting the following in apache2.2 log: [Mon Dec 28 00:31:02 2009] [error] ajp_read_header: ajp_ilink_receive failed [Mon Dec 28 00:31:02 2009] [error] (120006)APR does not understand this error code: proxy: read response failed from 127.0.0.1:8009 (localhost)

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  • 503 error Varnish cache when eAccelerator is started

    - by Netismine
    I have a Magento installation running on x-large Amazon server. I have Varnish, memcached and eAccelerator installed on the server. At first everything was working fine, but then at some point it stopped working, throwing 503 error with Varnish cache stamp below it. When I disable eaccelerator, error is gone and site is working. This is my eaccelerator config: extension="eaccelerator.so" eaccelerator.shm_size = "512" eaccelerator.cache_dir = "/var/cache/php-eaccelerator" eaccelerator.enable = "1" eaccelerator.optimizer = "1" eaccelerator.debug = 0 eaccelerator.log_file = "/var/log/httpd/eaccelerator_log" eaccelerator.name_space = "" eaccelerator.check_mtime = "1" eaccelerator.filter = "" eaccelerator.shm_ttl = "0" eaccelerator.shm_prune_period = "0" eaccelerator.shm_only = "0" eaccelerator.allowed_admin_path = "" any hints?

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  • How to know if my nginx is in good health?

    - by Howard
    I am running a nginx on EC2 (m1.small) for SSL termination. I am using 2 workers on Ubuntu, with latest nginx (stable), the network throughput is around 2Mbps and system load average is around 2 to 3. I am wondering if this system is in good health for now, e.g. what is the queue length (I know nginx can handle a lot of concurrent request, but I mean before the request is being served, how many of them need to wait before being served) what is the average queue time for a given request to be served. I want to know because if my nginx is cpu bounded (e.g. due to SSL), I will need to upgrade to a faster instance. My current nginx status Active connections: 4076 server accepts handled requests 90664283 90664283 104117012 Reading: 525 Writing: 81 Waiting: 3470

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  • MySQL com_select?

    - by symcbean
    I'm looking to tune my query cache a bit. According to 7.6.3.4. Query Cache Status and Maintenance in the manual: The Com_select value is given by this formula: Qcache_inserts + Qcache_not_cached + queries with errors found during the column-privileges check However in 5.1.5. Server Status Variables it suggests that this is maintained by the DBMS. Having said that mysql> show status like 'Com_select%'; Always returns a value of 1 - and I'm pretty sure I've run more than one non-cached select query on my database since it started. It looks as if other people are similarly confused. Is this status variable redundant? Which bit of the manual is wrong? TIA

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  • WAMP running extremely slow on WIndows 7

    - by JavaCake
    After 2 days of tough fight trying to figure out what the problem is with my Windows 7 32-bit machine at work i have nearly given up. The issue is that the pages are loaded extremely slow, the performance is both when accessed locally (127.0.0.1) or from another computer in the intranet. First to explain the system: WAMP version: Apache 2.2.22 – Mysql 5.5.24 – PHP 5.4.3 XDebug 2.1.2 XDC 1.5 PhpMyadmin 3.4.10.1 SQLBuddy 1.3.3 webGrind 1.0 DocumentRoot: Located on network drive MySQL: InnoDB Pages: PHP, MySQL, AJAX etc. So basically the changes i have made in order to get a greater performance: Changed C:\windows\system32\drivers\etc\hosts: 127.0.0.1 localhost 127.0.0.1 127.0.0.1 Modified my.ini: innodb_flush_log_at_trx_commit = 2 Modified httpd.ini: EnableMMAP on EnableSendfile on Modified php.ini: realpath_cache_size= 4m How i measure the performance is the overall loadtime of the page. I run it locally on my Mac OS X machine aswell (MAMP), and typically the frontpage loadtime is 0.06seconds but on the Windows 7 machine it is 6-10seconds. I have verified the loadtime with developertools in Chrome aswell. Furthermore the result is identical in XAMPP.

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  • What is bottleneck of my Apache server ?

    - by rrh
    $netstat -anp | grep :80 | grep TIME_WAIT | wc -l 840 $netstat -anp |grep :80 | grep ESTABLISHED | wc -l 50 memory usage : 850MB / 1000MB apache2.conf contains.. <IfModule mpm_prefork_module> StartServers 5 MinSpareServers 5 MaxSpareServers 10 MaxClients 150 MaxRequestsPerChild 0 </IfModule> <IfModule mpm_worker_module> StartServers 2 MinSpareThreads 25 MaxSpareThreads 75 ThreadLimit 64 ThreadsPerChild 25 MaxClients 150 MaxRequestsPerChild 0 </IfModule> <IfModule mpm_event_module> StartServers 2 MaxClients 150 MinSpareThreads 25 MaxSpareThreads 75 ThreadLimit 64 ThreadsPerChild 25 MaxRequestsPerChild 0 </IfModule> Are there any configuration changes that can help me or its just my RAM the bottleneck here? Urgent help needed..!!

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  • What are your tricks for optimizing your Subversion configuration?

    - by Scott Markwell
    For a Linux or Windows system, what tricks do you do to optimize your Subversion server? The following are my current tricks for a Linux system serving over Apache with HTTPS and backed by Active Directory using LDAP authentication. Enabling KeepAlive on Apache Disable SVNPathAuthz Increase LDAP Cache Using the FSFS storage method instead of BDB Feel free to call this into question. I don't have hard proof that FSFS out performs BDB, only lots of tribal knowledge and hearsay.

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  • Optimise Apache for EC2 micro instance

    - by Shiyu Sekam
    I'm running apache2 on a EC2 micro instance with ~600 mb RAM. The instance was running for almost a year without problems, but in the last weeks it just keeps crashing, because the server reached MaxClients. The server basically runs few websites, one wordpress blog(not often used), company website(most used) and 2 small sites, which are just internal. The database for the blog runs on RDS, so there's no Mysql running on this web server. When I came to the company, the server already was setup and is running apache + mod_php + prefork. We want to migrate that in the future to a nginx + php-fpm, but it still needs further testing. So for now I have to stick with the old setup. I also use CloudFlare DDOS protection in front of the server, because it was attacked a couple of the times in the last weeks. My company don't want to pay money for a better web server at this point, so I have to stick with the micro instance also. Additionally the code for the website we run is really bad and slow and sometimes a single page load can take up to 15 seconds. The whole website is dynamic and written in PHP, so caching isn't really an option here. It's a customized search for users. I've already turned off KeepAlive, which improved the performance a little bit. My prefork config looks like the following: StartServers 2 MinSpareServers 2 MaxSpareServers 5 ServerLimit 10 MaxClients 10 MaxRequestsPerChild 100 The server just becomes unresponsive after a while running and I've run the following command to see how many connections there are: netstat | grep http | wc -l 75 Trying to restart apache helps for a short moment, but after that a while the apache process(es) become unresponsive again. I've the following modules enabled(output of apache2ctl -M) Loaded Modules: core_module (static) log_config_module (static) logio_module (static) version_module (static) mpm_prefork_module (static) http_module (static) so_module (static) alias_module (shared) authz_host_module (shared) deflate_module (shared) dir_module (shared) expires_module (shared) mime_module (shared) negotiation_module (shared) php5_module (shared) rewrite_module (shared) setenvif_module (shared) ssl_module (shared) status_module (shared) Syntax OK apache2.conf # Security ServerTokens OS ServerSignature On TraceEnable On ServerName "web.example.com" ServerRoot "/etc/apache2" PidFile ${APACHE_PID_FILE} Timeout 30 KeepAlive off User www-data Group www-data AccessFileName .htaccess <Files ~ "^\.ht"> Order allow,deny Deny from all Satisfy all </Files> <Directory /> Options FollowSymLinks AllowOverride None </Directory> DefaultType none HostnameLookups Off ErrorLog /var/log/apache2/error.log LogLevel warn EnableSendfile On #Listen 80 Include /etc/apache2/mods-enabled/*.load Include /etc/apache2/mods-enabled/*.conf Include /etc/apache2/ports.conf LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined LogFormat "%h %l %u %t \"%r\" %>s %b" common LogFormat "%{Referer}i -> %U" referer LogFormat "%{User-agent}i" agent Include /etc/apache2/conf.d/*.conf Include /etc/apache2/sites-enabled/*.conf Vhost of main site <VirtualHost *:80> ServerName www.example.com ## Vhost docroot DocumentRoot /srv/www/jenkins/Web ## Directories, there should at least be a declaration for /srv/www/jenkins/Web <Directory /srv/www/jenkins/Web> AllowOverride All Order allow,deny Allow from all </Directory> ## Load additional static includes ## Logging ErrorLog /var/log/apache2/www.example.com.error.log LogLevel warn ServerSignature Off CustomLog /var/log/apache2/www.example.com.access.log combined ## Rewrite rules RewriteEngine On RewriteCond %{HTTP_HOST} !^www.example.com$ RewriteRule ^.*$ http://www.example.com%{REQUEST_URI} [R=301,L] ## Server aliases ServerAlias www.example.invalid ServerAlias example.com ## Custom fragment <Location /srv/www/jenkins/Web/library> Order Deny,Allow Deny from all </Location> <Files ~ "^\.(.+)"> Order deny,allow deny from all </Files> </VirtualHost>

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  • apache chokes after 300 connections

    - by john titus
    We have an apache webserver in front of Tomcat hosted on EC2, instance type is extra large with 34GB memory. Our application deals with lot of external webservices and we have a very lousy external webservice which takes almost 300 seconds to respond to requests during peak hours. During peak hours the server chokes at just about 300 httpd processes. ps -ef | grep httpd | wc -l =300 I have googled and found numerous suggestions but nothing seems to work.. following are some configuration i have done which are directly taken from online resources. I have increased the limits of max connection and max clients in both apache and tomcat. here are the configuration details: //apache <IfModule prefork.c> StartServers 100 MinSpareServers 10 MaxSpareServers 10 ServerLimit 50000 MaxClients 50000 MaxRequestsPerChild 2000 </IfModule> //tomcat <Connector port="8080" protocol="org.apache.coyote.http11.Http11NioProtocol" connectionTimeout="600000" redirectPort="8443" enableLookups="false" maxThreads="1500" compressableMimeType="text/html,text/xml,text/plain,text/css,application/x-javascript,text/vnd.wap.wml,text/vnd.wap.wmlscript,application/xhtml+xml,application/xml-dtd,application/xslt+xml" compression="on"/> //Sysctl.conf net.ipv4.tcp_tw_reuse=1 net.ipv4.tcp_tw_recycle=1 fs.file-max = 5049800 vm.min_free_kbytes = 204800 vm.page-cluster = 20 vm.swappiness = 90 net.ipv4.tcp_rfc1337=1 net.ipv4.tcp_max_orphans = 65536 net.ipv4.ip_local_port_range = 5000 65000 net.core.somaxconn = 1024 I have been trying numerous suggestions but in vain.. how to fix this? I'm sure m2xlarge server should serve more requests than 300, probably i might be going wrong with my configuration.. The server chokes only during peak hours and when there are 300 concurrent requests waiting for the [300 second delayed] webservice to respond. Please help..

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  • On ESXi, guest machines hang for significant intervals compared to real machines. How can I fix this?

    - by Tarbox
    This is ESXi version 5.0.0. We plan on upgrading to 5.5 eventually. I have four code profiles, two taken on a real, unvirtualized machine, two taken on a virtual machine. Ordering the list of subroutines by time spent in each one, the two real profiles are practically identical. The two virtual profiles are different from each other and from the real profiles: a subset of subroutines are taking a lot more time on the virtual machines, and the subset is different for each run. The two virtual profiles take a similar amount of time, which is 3 times the amount of time the real profiles take. This gross "how long does it take?" result is consistent after hundreds of tests across three different virtual machines on two different host machines -- the virtual machine is just slower. I've only the code profiling on the four, however. Here's the most guilty set of lines: This is the real machine: 8µs $text = '' unless defined $text; 1.48ms foreach ( split( "\n", $text ) ) { This is the first run on the virtual machine: 20.1ms $text = '' unless defined $text; 1.49ms foreach ( split( "\n", $text ) ) { This is the second run on the virtual machine: 6µs $text = '' unless defined $text; 21.9ms foreach ( split( "\n", $text ) ) { My WAG is that the VM is swapping out the thread and then swapping it back in, destroying some level of cache in the process, but these code profiles were taken when the vm in question was the only active vm on the host, so... what? What does that mean? The guest itself is under light load, this is a latency problem for my users rather than throughput. The host is also under a light load, if I knew what resources to assign where, I could do it without worrying about the cost. I've attempted to lock memory, reserve cpu, assign a restrictive affinity, and disable hyperthread sharing. They don't help, it still takes the VM 2-4x the amount of time to do the same thing as the real machine. The host the tests were run on is 6x2.50GHz, Intel Xeon E5-26400 w/ 16gigs of ram. The guest exhibits the same performance under a wide combination of settings. The real machine is 4x2.13GHz, Xeon E5506 w/ 2 gigs of ram. Thank you for all advice.

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  • Send request body data when running siege

    - by qui
    I am trying to use the command line utility Siege to load test a service. The service recieves json in the request body via a POST. I have a file called example-data.json with the json inside. I will eventually turn this into a tiny service which creates random json for testing, but this should do for now I have another file called hit-qa.siege with http://www.qa-url.com POST < example-data.json and i try and run siege -c10 -d1 -r1 -f ops/perf/hammer-dev.siege When I check the logs of the service, it is not recieving anything in the request body. My googles have been fruitless, does anyone know how to accomplish this?

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  • Specific apache + mysql settings for a light-weight site

    - by Good Person
    I have a small website with a Joomla and a Moodle set up. It seems that both of these are very slow. The server (CentOS release 5.5 (Final)) is a virtual dedicated server with about 2GB of ram. I don't expect to ever get more than 10-15 people on at the same time (and if that is high) What settings could I change in either apache, mysql, or even the OS to increase the performance of my site? I'm not concerned about running out of resources if I get too many visitors. If you need more specific data leave a comment and I'll edit the question.

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  • How to remove the pause during JBoss 5.1.0 GA boot between ProfileServiceBootstrap and AnnotationCreator?

    - by rrc7cz
    I've managed to strip down my JBoss profile enough that it boots in 1.5 minutes. I started with the web profile and started pulling out stuff I didn't need. The bulk of my boot time can be seen here: ... 15:21:51,890 INFO [ProfileServiceBootstrap] Loading profile: ProfileKey@86d597[domain=default, server=default, name=np] 15:22:55,406 WARN [AnnotationCreator] No ClassLoader provided, using TCCL: org.jboss.managed.api.annotation.ManagementComponent 15:22:55,578 WARN [AnnotationCreator] No ClassLoader provided, using TCCL: org.jboss.managed.api.annotation.ManagementComponent ... Does anyone have any idea what JBoss is doing here for 1 minute? If so, is there any way to speed it up or skip it entirely? This is for developer instances, so boot time is quite important.

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  • IIS6 - Classic ASP - "out of memory"/"out of string space"

    - by glaucon
    We have a classic ASP application that's under significantly more load than usual. We are from time to time been getting "out of memory" and "out of string space" in the httperr. We do not usually see these errors. For the moment we cannot change the application. Is there anything we can do to the IIS config which will help to reduce or stop these errors occurring ? The application pool is set to default values currently.

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  • Which memory related Tomcat JVM startup parameters are worth tuning?

    - by knorv
    I'm trying to understand the fine art of tuning Tomcat memory settings. In this quest I have the following three questions: Which memory related JVM startup parameters are worth setting when running Tomcat? Why? What are useful rule-of-thumbs when fine-tuning the memory settings for a Tomcat installation? How do you monitor the memory consumption of your live Tomcat installation?

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  • How can I avoid garbage collection delays in Java games? (Best Practices)

    - by Brian
    I'm performance tuning interactive games in Java for the Android platform. Once in a while there is a hiccup in drawing and interaction for garbage collection. Usually it's less than one tenth of a second, but sometimes it can be as large as 200ms on very slow devices. I am using the ddms profiler (part of the Android SDK) to search out where my memory allocations come from and excise them from my inner drawing and logic loops. The worst offender had been short loops done like, for(GameObject gob : interactiveObjects) gob.onDraw(canvas); where every single time the loop was executed there was an iterator allocated. I'm using arrays (ArrayList) for my objects now. If I ever want trees or hashes in an inner loop I know that I need to be careful or even reimplement them instead of using the Java Collections framework since I can't afford the extra garbage collection. That may come up when I'm looking at priority queues. I also have trouble where I want to display scores and progress using Canvas.drawText. This is bad, canvas.drawText("Your score is: " + Score.points, x, y, paint); because Strings, char arrays and StringBuffers will be allocated all over to make it work. If you have a few text display items and run the frame 60 times a second that begins to add up and will increase your garbage collection hiccups. I think the best choice here is to keep char[] arrays and decode your int or double manually into it and concatenate strings onto the beginning and end. I'd like to hear if there's something cleaner. I know there must be others out there dealing with this. How do you handle it and what are the pitfalls and best practices you've discovered to run interactively on Java or Android? These gc issues are enough to make me miss manual memory management, but not very much.

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  • Small performance test on a web service

    - by vtortola
    Hi, I'm trying to develop a small application that test how many requests per second can my service support but I think I'm doing something wrong. The service is in an early development stage, but I'd like to have this test handy in order to check in time to time I'm not doing something that decrease the performance. The problem is that I cannot get the web server or the database server go to the 100% of CPU. I'm using three different computers, in one is the web server (WinSrv Standard 2008 x64 IIS7), in other the database (Win 2K - SQL Server 2005) and the last is my computer (Win7 x64 ultimate), where I'll run the test. The computers are connected through a 100 ethernet switch. The request POST is 9 bytes and the response will be 842 bytes. The test launches several threads, and each thread has a "while" loop, in each loop it creates a WebRequest object, performs a call, increment a common counter and waits between 1 and 5 millisencods, then it do it again: static Int32 counter = 0; static void Main(string[] args) { ServicePointManager.DefaultConnectionLimit = 250; Console.WriteLine("Ready. Press any key..."); Console.ReadKey(); Console.WriteLine("Running..."); String localhost = "localhost"; String linuxmono = "192.168.1.74"; String server= "192.168.1.5:8080"; DateTime start = DateTime.Now; Random r = new Random(DateTime.Now.Millisecond); for (int i = 0; i < 50; i++) { new Thread(new ParameterizedThreadStart(Test)).Start(server); Thread.Sleep(r.Next(1, 3)); } Thread.Sleep(2000); while (true) { Console.WriteLine("Request per second :" + counter/DateTime.Now.Subtract(start).TotalSeconds ); Thread.Sleep(3000); } } public static void Test(Object ip) { Guid guid = Guid.NewGuid(); Random r = new Random(DateTime.Now.Millisecond); while (true) { String test = "<lalala/>"; WebRequest req = WebRequest.Create("http://" + (String)ip + "/WebApp/"+guid.ToString()+"/Data/Tables=whatever"); req.Method = "POST"; req.ContentType = "application/xml"; req.Credentials = new NetworkCredential("aaa", "aaa","domain"); Byte[] array = Encoding.UTF8.GetBytes(test); req.ContentLength = array.Length; using (Stream reqStream = req.GetRequestStream()) { reqStream.Write(array, 0, array.Length); reqStream.Close(); } using (Stream responseStream = req.GetResponse().GetResponseStream()) { String response = new StreamReader(responseStream).ReadToEnd(); if (response.Length != 842) Console.Write(" EEEE "); } Interlocked.Increment(ref counter); Thread.Sleep(r.Next(1,5)); } } If I run the test neither of the computers do an excesive CPU usage. Let's say I get a X requests per second, if I run the console application two times at the same moment, I get X/2 request per second in each one... but still the web server is on 30% of CPU, the database server on 25%... I've tried to remove the thread.sleep in the loop, but it doesn't make a big difference. I'd like to put the machines to the maximun, to check how may requests per second they can provide. I guessed that I could do it in this way... but apparently I'm missing something here... What is the problem? Kind regards.

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  • EF4 performance tips and tricks

    - by Will
    I've gotten to that point in one of my projects, and haven't found much information out there. So if you've got some pointers for improving performance in the new Entity Framework 4, please let us know!

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  • Python performance: iteration and operations on nested lists

    - by J.J.
    Problem Hey folks. I'm looking for some advice on python performance. Some background on my problem: Given: A mesh of nodes of size (x,y) each with a value (0...255) starting at 0 A list of N input coordinates each at a specified location within the range (0...x, 0...y) Increment the value of the node at the input coordinate and the node's neighbors within range Z up to a maximum of 255. Neighbors beyond the mesh edge are ignored. (No wrapping) BASE CASE: A mesh of size 1024x1024 nodes, with 400 input coordinates and a range Z of 75 nodes. Processing should be O(x*y*Z*N). I expect x, y and Z to remain roughly around the values in the base case, but the number of input coordinates N could increase up to 100,000. My goal is to minimize processing time. Current results I have 2 current implementations: f1, f2 Running speed on my 2.26 GHz Intel Core 2 Duo with Python 2.6.1: f1: 2.9s f2: 1.8s f1 is the initial naive implementation: three nested for loops. f2 is replaces the inner for loop with a list comprehension. Code is included below for your perusal. Question How can I further reduce the processing time? I'd prefer sub-1.0s for the test parameters. Please, keep the recommendations to native Python. I know I can move to a third-party package such as numpy, but I'm trying to avoid any third party packages. Also, I've generated random input coordinates, and simplified the definition of the node value updates to keep our discussion simple. The specifics have to change slightly and are outside the scope of my question. thanks much! f1 is the initial naive implementation: three nested for loops. 2.9s def f1(x,y,n,z): rows = [] for i in range(x): rows.append([0 for i in xrange(y)]) for i in range(n): inputX, inputY = (int(x*random.random()), int(y*random.random())) topleft = (inputX - z, inputY - z) for i in xrange(max(0, topleft[0]), min(topleft[0]+(z*2), x)): for j in xrange(max(0, topleft[1]), min(topleft[1]+(z*2), y)): if rows[i][j] <= 255: rows[i][j] += 1 f2 is replaces the inner for loop with a list comprehension. 1.8s def f2(x,y,n,z): rows = [] for i in range(x): rows.append([0 for i in xrange(y)]) for i in range(n): inputX, inputY = (int(x*random.random()), int(y*random.random())) topleft = (inputX - z, inputY - z) for i in xrange(max(0, topleft[0]), min(topleft[0]+(z*2), x)): l = max(0, topleft[1]) r = min(topleft[1]+(z*2), y) rows[i][l:r] = [j+1 for j in rows[i][l:r] if j < 255]

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  • Performance penalty of typecasting and boxing/unboxing types in C# when storing generic values

    - by kitsune
    I have a set-up similar to WPF's DependencyProperty and DependencyObject system. My properties however are generic. A BucketProperty has a static GlobalIndex (defined in BucketPropertyBase) which tracks all BucketProperties. A Bucket can have many BucketProperties of any type. A Bucket saves and gets the actual values of these BucketProperties... now my question is, how to deal with the storage of these values, and what is the penalty of using a typecasting when retrieving them? I currently use an array of BucketEntries that save the property values as simple objects. Is there any better way of saving and returning these values? Beneath is a simpliefied version: public class BucketProperty<T> : BucketPropertyBase { } public class Bucket { private BucketEntry[] _bucketEntries; public void SaveValue<T>(BucketProperty<T> property, T value) { SaveBucketEntry(property.GlobalIndex, value) } public T GetValue<T>(BucketProperty<T> property) { return (T)FindBucketEntry(property.GlobalIndex).Value; } } public class BucketEntry { private object _value; private uint _index; public BucketEntry(uint globalIndex, object value) { ... } }

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  • Avoiding denormal values in C++

    - by Nathan
    Hi, After search a long time for a performance bug, I read abut denormal foating point values. I have an Intel Core 2 Duo and I am compiling with gcc, using "-O2". So what do I do? Can I somehow instruct g++ to avoid denormal values? If not, can I somehow test if a float is denormal? Thanks! Nathan

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