posix/sched_cpucount.c

   1 /* Copyright (C) 2007-2021 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <sched.h>
  19
  20 /* Counting bits set, Brian Kernighan's way.
  21    Using a open-coded routine is slight better for architectures that
  22    do not have a popcount instruction (compiler might emit a library
  23    call).  */
  24 static inline int
  25 countbits (__cpu_mask v)
  26 {
  27   int s = 0;
  28   for (; v != 0; s++)
  29     v &= v - 1;
  30   return s;
  31 }
  32
  33 int
  34 __sched_cpucount (size_t setsize, const cpu_set_t *setp)
  35 {
  36   int s = 0;
  37   for (int i = 0; i < setsize / sizeof (__cpu_mask); i++)
  38     s += countbits (setp->__bits[i]);
  39   return s;
  40 }
  41 libc_hidden_def (__sched_cpucount)