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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.
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2 changed files with 38 additions and 1 deletions
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@ -10,6 +10,8 @@
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#
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# Supported methods:
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# - GetSystemInfo(): Windows (including Cygwin)
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# - sched_getaffinity(): glibc (GNU/Linux, GNU/kFreeBSD)
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# - cpuset_getaffinity(): FreeBSD
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# - sysctl(): BSDs, OS/2
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# - sysconf(): GNU/Linux, Solaris, Tru64, IRIX, AIX, QNX, Cygwin (but
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# GetSystemInfo() is used on Cygwin)
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@ -45,8 +47,29 @@ compile error
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#endif
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]])], [tuklib_cv_cpucores_method=special], [
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# glibc-based systems (GNU/Linux and GNU/kFreeBSD) have sched_getaffinity().
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# The CPU_COUNT() macro was added in glibc 2.9 so we try to link the
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# test program instead of merely compiling it. glibc 2.9 is old enough that
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# if someone uses the code on older glibc, the fallback to sysconf() should
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# be good enough.
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AC_LINK_IFELSE([AC_LANG_SOURCE([[
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#include <sched.h>
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int
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main(void)
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{
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cpu_set_t cpu_mask;
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sched_getaffinity(0, sizeof(cpu_mask), &cpu_mask);
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return CPU_COUNT(&cpu_mask);
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}
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]])], [tuklib_cv_cpucores_method=sched_getaffinity], [
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# FreeBSD has both cpuset and sysctl. Look for cpuset first because
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# it's a better approach.
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#
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# This test would match on GNU/kFreeBSD too but it would require
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# -lfreebsd-glue when linking and thus in the current form this would
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# fail on GNU/kFreeBSD. The above test for sched_getaffinity() matches
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# on GNU/kFreeBSD so the test below should never run on that OS.
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AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
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#include <sys/param.h>
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#include <sys/cpuset.h>
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@ -120,9 +143,14 @@ main(void)
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]])], [tuklib_cv_cpucores_method=pstat_getdynamic], [
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tuklib_cv_cpucores_method=unknown
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])])])])])])
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])])])])])])])
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case $tuklib_cv_cpucores_method in
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sched_getaffinity)
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AC_DEFINE([TUKLIB_CPUCORES_SCHED_GETAFFINITY], [1],
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[Define to 1 if the number of available CPU cores
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can be detected with sched_getaffinity()])
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;;
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cpuset)
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AC_DEFINE([TUKLIB_CPUCORES_CPUSET], [1],
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[Define to 1 if the number of available CPU cores
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@ -18,6 +18,10 @@
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# endif
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# include <windows.h>
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// glibc >= 2.9
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#elif defined(TUKLIB_CPUCORES_SCHED_GETAFFINITY)
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# include <sched.h>
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// FreeBSD
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#elif defined(TUKLIB_CPUCORES_CPUSET)
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# include <sys/param.h>
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@ -49,6 +53,11 @@ tuklib_cpucores(void)
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GetSystemInfo(&sysinfo);
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ret = sysinfo.dwNumberOfProcessors;
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#elif defined(TUKLIB_CPUCORES_SCHED_GETAFFINITY)
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cpu_set_t cpu_mask;
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if (sched_getaffinity(0, sizeof(cpu_mask), &cpu_mask) == 0)
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ret = CPU_COUNT(&cpu_mask);
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#elif defined(TUKLIB_CPUCORES_CPUSET)
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cpuset_t set;
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if (cpuset_getaffinity(CPU_LEVEL_WHICH, CPU_WHICH_PID, -1,
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