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authorakr <akr@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>2014-10-15 09:41:25 +0000
committerakr <akr@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>2014-10-15 09:41:25 +0000
commit7d9e04de496915dd9e4544ee18b1a0026dc79242 (patch)
tree2a7f2cdeb7ce71bb20b04e3d0d3e05ae2535ead7 /ext/etc
parente1ba2d418ad6f4e9e63e9db05ff5602e0f379652 (diff)
* 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. [Feature #10267] etc-nprocessors-kosaki2.patch git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47939 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Diffstat (limited to 'ext/etc')
-rw-r--r--ext/etc/etc.c72
1 files changed, 72 insertions, 0 deletions
diff --git a/ext/etc/etc.c b/ext/etc/etc.c
index 94b9cc3..aaa5025 100644
--- a/ext/etc/etc.c
+++ b/ext/etc/etc.c
@@ -30,6 +30,10 @@
#include <sys/utsname.h>
#endif
+#ifdef HAVE_SCHED_GETAFFINITY
+#include <sched.h>
+#endif
+
static VALUE sPasswd;
#ifdef HAVE_GETGRENT
static VALUE sGroup;
@@ -904,6 +908,54 @@ io_pathconf(VALUE io, VALUE arg)
#endif
#if (defined(HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)) || defined(_WIN32)
+
+#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.
*
@@ -912,12 +964,21 @@ io_pathconf(VALUE io, VALUE arg)
*
* 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)
@@ -925,6 +986,17 @@ etc_nprocessors(VALUE obj)
long ret;
#if !defined(_WIN32)
+
+#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) {