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Feature #10267 » etc-nprocessors-kosaki2.patch

kosaki (Motohiro KOSAKI), 10/01/2014 09:48 PM

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ChangeLog
Thu Oct 2 05:50:59 2014 KOSAKI Motohiro <kosaki.motohiro@gmail.com>
* ext/etc/etc.c (etc_nprocessors_affinity): use sched_getaffinity
for getting precious number of available cpus.
* ext/etc/etc.c (etc_nprocessors): use etc_nprocessors_affinity if
possible.
Thu Oct 2 03:42:12 2014 Tanaka Akira <akr@fsij.org>
* ext/etc/etc.c (etc_nprocessors_online): New method.
configure.in
AC_CHECK_FUNCS(qsort_r)
AC_CHECK_FUNCS(readlink)
AC_CHECK_FUNCS(round)
AC_CHECK_FUNCS(sched_getaffinity)
AC_CHECK_FUNCS(seekdir)
AC_CHECK_FUNCS(select_large_fdset)
AC_CHECK_FUNCS(sendfile)
ext/etc/etc.c
#include <sys/utsname.h>
#endif
#ifdef HAVE_SCHED_GETAFFINITY
#include <sched.h>
#endif
static VALUE sPasswd;
#ifdef HAVE_GETGRENT
static VALUE sGroup;
......
#define io_pathconf rb_f_notimplement
#endif
#if defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
#ifdef HAVE_SCHED_GETAFFINITY
static int
etc_nprocessors_affin(void)
{
cpu_set_t *cpuset;
size_t size;
int ret;
int ncpus;
/*
* XXX:
* man page says CPU_ALLOC takes number of cpus. But it is not accurate
* explanation. sched_getaffinity() returns EINVAL if cpuset bitmap is
* smaller than kernel internal bitmap.
* That said, sched_getaffinity() can fail when a kernel have sparse bitmap
* even if cpuset bitmap is larger than number of cpus.
* The precious way is to use /sys/devices/system/cpu/online. But there are
* two problems,
* - Costly calculation
* It is minor issue, but possibly kill the benefit of parallel processing.
* - No guarantee to exist /sys/devices/system/cpu/online
* This is an issue especially when using containers.
* So, we use hardcode number for workaround. Current linux kernel
* (Linux 3.17) support 8192 cpus at maximum. Then 16384 is enough large.
*/
ncpus = 16384;
cpuset = CPU_ALLOC(ncpus);
if (!cpuset) {
return -1
}
size = CPU_ALLOC_SIZE(ncpus);
CPU_ZERO_S(size, cpuset);
ret = sched_getaffinity(0, size, cpuset);
if (ret==-1) {
goto free;
}
ret = CPU_COUNT_S(size, cpuset);
free:
CPU_FREE(cpuset);
return ret;
}
#endif
/*
* Returns the number of online processors.
*
......
*
* This method is implemented as:
* - sysconf(_SC_NPROCESSORS_ONLN): GNU/Linux, NetBSD, FreeBSD, OpenBSD, DragonFly BSD, OpenIndiana, Mac OS X, AIX
* - sched_getaffinity(): Linux
*
* Example:
*
* require 'etc'
* p Etc.nprocessors #=> 4
*
* The result might be smaller number than physical cpus especially when ruby
* process is bound to specific cpus. This is intended for getting better
* parallel processing.
*
* Example: (Linux)
*
* $ taskset 0x3 ./ruby -retc -e "p Etc.nprocessors" #=> 2
*
*/
static VALUE
etc_nprocessors(VALUE obj)
{
long ret;
#ifdef HAVE_SCHED_GETAFFINITY
int ncpus;
ncpus = etc_nprocessors_affin();
if (ncpus != -1) {
return INT2NUM(ncpus);
}
/* fallback to _SC_NPROCESSORS_ONLN */
#endif
errno = 0;
ret = sysconf(_SC_NPROCESSORS_ONLN);
if (ret == -1) {
rb_sys_fail("sysconf(_SC_NPROCESSORS_ONLN)");
}
return LONG2NUM(ret);
}
#else
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