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Use CPU_COUNT to get the number of set CPUs

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This fixes an issue with the number getting very big due to
CPU_ISSET not returning exactly 0 or 1.

This also fixes scenarios where there are holes in the CPU
set. E.g. for a simple run like `taskset --cpu-list 1,2,4 ...`
the old code would return 2 instead of 3, due to iterating
until `ncores` (which is 3) and therefore not accounting for
CPUs further in the set.

Ref https://gitlab.gnome.org/GNOME/glib/-/merge_requests/3784
This commit is contained in:
q66 2024-03-23 20:51:52 +01:00
parent e124c34ad6
commit cc25486b23
1 changed files with 1 additions and 3 deletions
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4
glib/gthread.c
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@ -1092,7 +1092,6 @@ g_get_num_processors (void)
return count;
#elif defined(_SC_NPROCESSORS_ONLN) && defined(THREADS_POSIX) && defined(HAVE_PTHREAD_GETAFFINITY_NP)
{
int idx;
int ncores = MIN (sysconf (_SC_NPROCESSORS_ONLN), CPU_SETSIZE);
cpu_set_t cpu_mask;
CPU_ZERO (&cpu_mask);
@ -1100,8 +1099,7 @@ g_get_num_processors (void)
int af_count = 0;
int err = pthread_getaffinity_np (pthread_self (), sizeof (cpu_mask), &cpu_mask);
if (!err)
for (idx = 0; idx < ncores && idx < CPU_SETSIZE; ++idx)
af_count += CPU_ISSET (idx, &cpu_mask);
af_count = CPU_COUNT (&cpu_mask);
int count = (af_count > 0) ? af_count : ncores;
return count;