Back to index

glibc  2.9
prof-freq.c
Go to the documentation of this file.
00001 /* Determine realtime clock frequency.
00002    Copyright (C) 2003, 2004, 2006 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <sys/time.h>
00021 #include <libc-internal.h>
00022 #include <kernel-features.h>
00023 #include <ldsodefs.h>
00024 
00025 
00026 int
00027 __profile_frequency (void)
00028 {
00029 #ifdef __ASSUME_AT_CLKTCK
00030   return GLRO(dl_clktck);
00031 #else
00032   if (GLRO(dl_clktck) != 0)
00033     return GLRO(dl_clktck);
00034 
00035   struct itimerval tim;
00036 
00037   tim.it_interval.tv_sec = 0;
00038   tim.it_interval.tv_usec = 1;
00039   tim.it_value.tv_sec = 0;
00040   tim.it_value.tv_usec = 0;
00041 
00042   __setitimer (ITIMER_REAL, &tim, 0);
00043   __setitimer (ITIMER_REAL, 0, &tim);
00044 
00045   if (tim.it_interval.tv_usec < 2)
00046     return 0;
00047 
00048   return 1000000 / tim.it_interval.tv_usec;
00049 #endif
00050 }
00051 libc_hidden_def (__profile_frequency)