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tuklib_cpucores: Add support for sched_getaffinity(). 

It's available in glibc (GNU/Linux, GNU/kFreeBSD). It's better
than sysconf(_SC_NPROCESSORS_ONLN) because sched_getaffinity()
gives the number of cores available to the process instead of
the total number of cores online.

As a side effect, this commit fixes a bug on GNU/kFreeBSD where
configure would detect the FreeBSD-specific cpuset_getaffinity()
but it wouldn't actually work because on GNU/kFreeBSD it requires
using -lfreebsd-glue when linking. Now the glibc-specific function
will be used instead.

Thanks to Sebastian Andrzej Siewior for the original patch
and testing.
This commit is contained in:
Lasse Collin 2016-10-24 18:51:36 +03:00
parent 51baf68437
commit 88d7a7fd15
2 changed files with 38 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
m4/tuklib_cpucores.m4
View File

@ -10,6 +10,8 @@
#
# Supported methods:
# - GetSystemInfo(): Windows (including Cygwin)
# - sched_getaffinity(): glibc (GNU/Linux, GNU/kFreeBSD)
# - cpuset_getaffinity(): FreeBSD
# - sysctl(): BSDs, OS/2
# - sysconf(): GNU/Linux, Solaris, Tru64, IRIX, AIX, QNX, Cygwin (but
# GetSystemInfo() is used on Cygwin)
@ -45,8 +47,29 @@ compile error
#endif
]])], [tuklib_cv_cpucores_method=special], [
# glibc-based systems (GNU/Linux and GNU/kFreeBSD) have sched_getaffinity().
# The CPU_COUNT() macro was added in glibc 2.9 so we try to link the
# test program instead of merely compiling it. glibc 2.9 is old enough that
# if someone uses the code on older glibc, the fallback to sysconf() should
# be good enough.
AC_LINK_IFELSE([AC_LANG_SOURCE([[
#include <sched.h>
int
main(void)
{
cpu_set_t cpu_mask;
sched_getaffinity(0, sizeof(cpu_mask), &cpu_mask);
return CPU_COUNT(&cpu_mask);
}
]])], [tuklib_cv_cpucores_method=sched_getaffinity], [
# FreeBSD has both cpuset and sysctl. Look for cpuset first because
# it's a better approach.
#
# This test would match on GNU/kFreeBSD too but it would require
# -lfreebsd-glue when linking and thus in the current form this would
# fail on GNU/kFreeBSD. The above test for sched_getaffinity() matches
# on GNU/kFreeBSD so the test below should never run on that OS.
AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
#include <sys/param.h>
#include <sys/cpuset.h>
@ -120,9 +143,14 @@ main(void)
]])], [tuklib_cv_cpucores_method=pstat_getdynamic], [
tuklib_cv_cpucores_method=unknown
])])])])])])
])])])])])])])
case $tuklib_cv_cpucores_method in
sched_getaffinity)
AC_DEFINE([TUKLIB_CPUCORES_SCHED_GETAFFINITY], [1],
[Define to 1 if the number of available CPU cores
can be detected with sched_getaffinity()])
;;
cpuset)
AC_DEFINE([TUKLIB_CPUCORES_CPUSET], [1],
[Define to 1 if the number of available CPU cores

9
src/common/tuklib_cpucores.c
View File

@ -18,6 +18,10 @@
# endif
# include <windows.h>
// glibc >= 2.9
#elif defined(TUKLIB_CPUCORES_SCHED_GETAFFINITY)
# include <sched.h>
// FreeBSD
#elif defined(TUKLIB_CPUCORES_CPUSET)
# include <sys/param.h>
@ -49,6 +53,11 @@ tuklib_cpucores(void)
GetSystemInfo(&sysinfo);
ret = sysinfo.dwNumberOfProcessors;
#elif defined(TUKLIB_CPUCORES_SCHED_GETAFFINITY)
cpu_set_t cpu_mask;
if (sched_getaffinity(0, sizeof(cpu_mask), &cpu_mask) == 0)
ret = CPU_COUNT(&cpu_mask);
#elif defined(TUKLIB_CPUCORES_CPUSET)
cpuset_t set;
if (cpuset_getaffinity(CPU_LEVEL_WHICH, CPU_WHICH_PID, -1,