Comments on: More information on pthread_setaffinity_np and sched_setaffinity http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/ A Blog on Parallel Programming and Concurrency by Michael Suess Sat, 31 Jul 2010 08:30:28 +0000 http://wordpress.org/?v=2.7 hourly 1 By: glass http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/comment-page-1/#comment-98559 glass Sat, 29 May 2010 02:46:11 +0000 http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/#comment-98559 call can not handle the whole affinity mask of the process, so it is impossible to move a process with many threads with one sched_setaffinity call can not handle the whole affinity mask of the process, so it is impossible to move a process with many threads with one sched_setaffinity

]]> By: manas http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/comment-page-1/#comment-98519 manas Fri, 16 Apr 2010 15:58:04 +0000 http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/#comment-98519 I tried using this function to bind two cores using two threads... but i noticed that the function is not binding threads to the cores. when the threads are reading the values from shared memory ,means they have the same data set to work upon in that case scheduler is running both the threads on the same core irrespective of this function. I came to know by looking at the system monitor and the time of execution. even after using the threads the execution time was coming out to be approximately equal to the sequential code. Can anybody help me with this ... can somebody give us a good example like the above one on sched_setaffinity... when i tried to use this function in the threads which are using totally different data sets then this functon worked perfectly . thanks for the example I tried using this function to bind two cores using two threads… but i noticed that
the function is not binding threads to the cores. when the threads are reading the values from shared memory ,means they have the same data set to work upon in that case scheduler is running both the threads on the same core irrespective of this function. I came to know by looking at the system monitor and the time of execution. even after using the threads the execution time was coming out to be approximately equal to the sequential code. Can anybody help me with this … can somebody give us a good example like the above one on sched_setaffinity…

when i tried to use this function in the threads which are using totally different data sets then this functon worked perfectly . thanks for the example

]]> By: John http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/comment-page-1/#comment-98510 John Fri, 26 Mar 2010 11:17:49 +0000 http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/#comment-98510 I har run my multithreaded application on a quad core but even I used pthread_setaffinity_np and it seems to set the affinity of each thread on the desired CPU-CORE, also TOP utility show that each core is loaded but the time reports that for a given TASK isung one THREAD it takes T seconds.millis...while for the same task spreaded on N=4 THREADS it takes 4xT secconds.millis...so four times longer which proves that there isn't parallelism...strange I har run my multithreaded application on a quad core but even I used pthread_setaffinity_np and it seems to set the affinity of each thread on the desired CPU-CORE, also TOP utility show that each core is loaded but the time reports that for a given TASK isung one THREAD it takes T seconds.millis…while for the same task spreaded on N=4 THREADS it takes 4xT secconds.millis…so four times longer which proves that there isn’t parallelism…strange

]]> By: tommy http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/comment-page-1/#comment-98435 tommy Wed, 10 Feb 2010 06:16:32 +0000 http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/#comment-98435 <blockquote> np stands for "non-portable" http://www.kernel.org/doc/man-pages/online/pages/man3/pthread_setaffinity_np.3.html I tried this function on an Intel Core2 Duo processor with two threads to run on the two cores. printf outputs tell me that all was well but the system monitor shows me that only one of the cores is being utilized. (The same application with OpenMP uses both cores). Anything i missed? Thanks

np stands for “non-portable”
http://www.kernel.org/doc/man-pages/online/pages/man3/pthread_setaffinity_np.3.html

I tried this function on an Intel Core2 Duo processor with two threads to run on the two cores. printf outputs tell me that all was well but the system monitor shows me that only one of the cores is being utilized. (The same application with OpenMP uses both cores). Anything i missed? Thanks

]]> By: Pradeep http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/comment-page-1/#comment-97910 Pradeep Tue, 30 Jun 2009 00:40:34 +0000 http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/#comment-97910 Hi, Any idea about "pthread_setaffinity" version, not _np (non preemptive) version? I am on a project that require job to be preempt on a single processor. (This is an experiment) -Pradeep Hi,
Any idea about “pthread_setaffinity” version, not _np (non preemptive) version?
I am on a project that require job to be preempt on a single processor. (This is an experiment)

-Pradeep

]]> By: Ramki http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/comment-page-1/#comment-97620 Ramki Fri, 27 Feb 2009 23:54:39 +0000 http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/#comment-97620 in the previous post, s,/lib64/tls/nptl,/usr/lib64/nptl, - Ramki in the previous post, s,/lib64/tls/nptl,/usr/lib64/nptl,

- Ramki

]]> By: Ramki http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/comment-page-1/#comment-97619 Ramki Fri, 27 Feb 2009 23:47:00 +0000 http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/#comment-97619 Turns out that RHEL doesn't find the right NPTL enabled libpthread.so by default. Trying with -L/lib64/tls/nptl on RHEL works (without the _GNU_SOURCE define). - Ramki Balasubramanian ramki_b@acm.org Turns out that RHEL doesn’t find the right NPTL enabled libpthread.so by default. Trying with -L/lib64/tls/nptl on RHEL works (without the _GNU_SOURCE define).

-
Ramki Balasubramanian
ramki_b@acm.org

]]> By: antx http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/comment-page-1/#comment-64132 antx Fri, 06 Jun 2008 00:40:43 +0000 http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/#comment-64132 After inspecting my headers a week ago I found that the pthread_setaffinity_np() is located inside a #ifdef GNU or something similar, then after some googling I found that in order to link the function you MUST use -D_GNU_SOURCE, so try appending it to GCC! Luck & Happy hacking. After inspecting my headers a week ago I found that the pthread_setaffinity_np() is located inside a #ifdef GNU or something similar,
then after some googling I found that in order to link the function you MUST use -D_GNU_SOURCE, so try appending it to GCC!

Luck & Happy hacking.

]]> By: Bert Wesarg http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/comment-page-1/#comment-6287 Bert Wesarg Wed, 11 Apr 2007 13:55:22 +0000 http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/#comment-6287 two notes: (1) pthread_setaffinity_np() is just a wrapper around sched_setaffinity() with the tid from the thread described by the pthread_t. this can be see here http://tinyurl.com/2slkve and here http://tinyurl.com/yobmfb (first note). (2) because of this, the sched_setaffinity() call can not handle the whole affinity mask of the process, so it is impossible to move a process with many threads with one sched_setaffinity() call to an other set of cpus. and the kernel does also not make a different between a process and a thread, which can be see here http://tinyurl.com/2kdu4f. two notes:

(1) pthread_setaffinity_np() is just a wrapper around sched_setaffinity() with the tid from the thread described by the pthread_t. this can be see here http://tinyurl.com/2slkve and here http://tinyurl.com/yobmfb (first note).

(2) because of this, the sched_setaffinity() call can not handle the whole affinity mask of the process, so it is impossible to move a process with many threads with one sched_setaffinity() call to an other set of cpus. and the kernel does also not make a different between a process and a thread, which can be see here http://tinyurl.com/2kdu4f.

]]> By: charles http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/comment-page-1/#comment-3060 charles Thu, 01 Mar 2007 22:37:46 +0000 http://www.thinkingparallel.com/2006/08/18/more-information-on-pthread_setaffinity_np-and-sched_setaffinity/#comment-3060 you have to #include "nptl/pthread.h" not pthread.h, which will probably use the linuxthreads header file which doesn't have the affinity methods. you will also need to do a -I/usr/include/nptl and -L/usr/lib/nptl. be aware you're breaking your program's compatibility with linuxthreads as a result. http://osmirrors.cerias.purdue.edu/pub/slackware/slackware-10.2/README.NPTL explains it all. you have to #include “nptl/pthread.h” not pthread.h, which will probably use the linuxthreads header file which doesn’t have the affinity methods. you will also need to do a -I/usr/include/nptl and -L/usr/lib/nptl. be aware you’re breaking your program’s compatibility with linuxthreads as a result. http://osmirrors.cerias.purdue.edu/pub/slackware/slackware-10.2/README.NPTL explains it all.

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