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.
diff --git a/m4/tuklib_cpucores.m4 b/m4/tuklib_cpucores.m4
index 468c2db..a2b09a7 100644
--- a/m4/tuklib_cpucores.m4
+++ b/m4/tuklib_cpucores.m4
@@ -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 @@
#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 @@
]])], [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
diff --git a/src/common/tuklib_cpucores.c b/src/common/tuklib_cpucores.c
index e235fd1..c16e188 100644
--- a/src/common/tuklib_cpucores.c
+++ b/src/common/tuklib_cpucores.c
@@ -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 @@
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,
