glibc/posix/sched_cpucount.c

42 lines
1.3 KiB
C

/* Copyright (C) 2007-2022 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sched.h>
/* Counting bits set, Brian Kernighan's way.
Using a open-coded routine is slight better for architectures that
do not have a popcount instruction (compiler might emit a library
call). */
static inline int
countbits (__cpu_mask v)
{
int s = 0;
for (; v != 0; s++)
v &= v - 1;
return s;
}
int
__sched_cpucount (size_t setsize, const cpu_set_t *setp)
{
int s = 0;
for (int i = 0; i < setsize / sizeof (__cpu_mask); i++)
s += countbits (setp->__bits[i]);
return s;
}
libc_hidden_def (__sched_cpucount)