On Wed, Nov 12, 2008 at 22:54, Loic Domaigne <tech@xxxxxxxxxxxx> wrote:> Hi Michael,>> see my comments below (refer also to my comments for> pthread_setaffinity_np.3).>> Cheers,> Loïc.> -->>> .\" Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk>> .\" <mtk.manpages@xxxxxxxxx>>> .\">> .\" Permission is granted to make and distribute verbatim copies of this>> .\" manual provided the copyright notice and this permission notice are>> .\" preserved on all copies.>> .\">> .\" Permission is granted to copy and distribute modified versions of this>> .\" manual under the conditions for verbatim copying, provided that the>> .\" entire resulting derived work is distributed under the terms of a>> .\" permission notice identical to this one.>> .\">> .\" Since the Linux kernel and libraries are constantly changing, this>> .\" manual page may be incorrect or out-of-date. The author(s) assume no>> .\" responsibility for errors or omissions, or for damages resulting from>> .\" the use of the information contained herein. The author(s) may not>> .\" have taken the same level of care in the production of this manual,>> .\" which is licensed free of charge, as they might when working>> .\" professionally.>> .\">> .\" Formatted or processed versions of this manual, if unaccompanied by>> .\" the source, must acknowledge the copyright and authors of this work.>> .\">> .TH PTHREAD_ATTR_SETAFFINITY_NP 3 2008-11-05 "Linux" "Linux Programmer's>> Manual">> Title looks weird on a 80x24 terminal.>>>> .SH NAME>> pthread_attr_setaffinity_np, pthread_attr_getaffinity_np \- set/get>> CPU affinity of a thread>> You surely mean: "CPU affinity attribute of a thread">>>> .SH SYNOPSIS>> .nf>> .B #define _GNU_SOURCE>> .B #include <pthread.h>>>>> .BI "int pthread_attr_setaffinity_np(pthread_attr_t " attr ,>> .BI " size_t " cpusetsize ", const cpu_set_t *" cpuset>> );>> .BI "int pthread_attr_getaffinity_np(pthread_attr_t " attr ,>> .BI " size_t " cpusetsize ", cpu_set_t *" cpuset );>> .sp>> Compile and link with \fI\-pthread\fP.>> .SH DESCRIPTION>> The>> .BR pthread_attr_setaffinity_np ()>> sets the CPU affinity mask attribute of the>> thread attributes object referred to by>> .I attr>> to the value specified in>> .IR cpuset .>> This attribute determines the CPU affinity mask>> of a thread created using the thread attributes object>> .IR attr .>>>> The>> .BR pthread_attr_getaffinity_np ()>> returns the CPU affinity mask attribute of the thread attributes object>> referred to by>> .IR attr>> in the buffer pointed to by>> .IR cpuset .>>>> The argument>> .I cpusetsize>> is the length (in bytes) of the buffer pointed to by>> .IR cpuset .>> Normally this argument would be specified as>> .IR sizeof(cpu_set_t) .>> The constant>> .B CPU_SETSIZE>> specifies a value one greater than the>> maximum CPU number that can be stored in a CPU set.>>>> For more details on CPU affinity masks,>> as well as a description of a set of macros>> that can be used to manipulate and inspect CPU sets, see>> .BR sched_setaffinity (2)>> for details.>> .SH RETURN VALUE>> On success, these functions return 0;>> on error, they return a non-zero error number.>> .SH ERRORS>> .TP>> .B EINVAL>> .I attr>> or>> .I cpuset>> is invalid.>> I beg your pardon, but I couldn't find where those checks are performed in> the relevant glibc files... Perhaps I am not looking at the right place?>>> .TP>> .BR EINVAL>> .RB ( pthread_attr_setaffinity_np ())>> .I cpuset>> specified a CPU that was outside the range>> permitted by the kernel data type>> .\" cpumask_t>> used to represent CPU sets.>> .\" The raw sched_getaffinity() system call returns the size (in bytes)>> .\" of the cpumask_t type.>> This range is determined by the kernel configuration option>> .BR CONFIG_NR_CPUS .>> <check>> Hmmm. What does happen if CPU set contains no CPU physically on the system> when the thread is created? I guess pthread_create() fails?> </check>>>> .TP>> .B EINVAL>> .RB ( pthread_getaffinity_np ())>> This should be: pthread_attr_getaffinity_np().>>>> A CPU in the affinity mask of the thread attributes object referred to by>> .I attr>> lies outside the range specified by>> .IR cpusetsize .>> For the application programmer, this means that the structure I passed for> storing the CPU set wasn't big enough to store thread's CPU set without> loosing "affinity information".>>>> .TP>> .B ENOMEM>> .RB ( pthread_attr_setaffinity_np ())>> Could not allocate memory.>> Correct. However, the glibc looks somewhat suspicious to me: I had expected> the memory allocated by iattr->cpuset to be bounded (by the size of the> underlying kernel structure).But this kernel structure is not bounded, it depends on the compiletime constant CONFIG_NR_CPUS (or in the future on the kernel runtimevariable nr_cpus_id), therefore glibc can't know this a-priori. (but Ihaven't looked into the code)
>> Or perhaps I am just missing my coffeine :o>>> .SH VERSIONS>> These functions are provided by glibc since version 2.3.4.>> .SH CONFORMING TO>> These functions are non-standard GNU extensions;>> hence the suffix "_np" (non-portable) in the names.>> .SH NOTES>> In glibc 2.3.3 only,>> versions of these functions were provided that did not have a>> .I cpusetsize>> argument.>> Instead the CPU set size given to the underlying system calls was always>> .IR sizeof(cpu_set_t) .>> .SH SEE ALSO>> .BR sched_setaffinity (2),>> .BR sched_setscheduler (2),>> Why the reference to sched_setscheduler()?>>> .BR pthread_attr_init (3),>> .BR pthread_setaffinity_np (3),>> .BR cpuset (7),>> .BR pthreads (7)>>>>��.n��������+%������w��{.n�����{��f��)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
