From 852eb34d5c56bc75bdd82327fcf310d98655f6b0 Mon Sep 17 00:00:00 2001 From: Ulrich Drepper Date: Wed, 22 Jun 2011 09:50:39 -0400 Subject: Rate limit expensive _SC_NPROCESSORS_ONLN computation --- sysdeps/unix/sysv/linux/getsysstats.c | 32 +++++++++++++++++++++++++++++++- 1 file changed, 31 insertions(+), 1 deletion(-) (limited to 'sysdeps/unix/sysv') diff --git a/sysdeps/unix/sysv/linux/getsysstats.c b/sysdeps/unix/sysv/linux/getsysstats.c index af454b650d..a13b6e3e37 100644 --- a/sysdeps/unix/sysv/linux/getsysstats.c +++ b/sysdeps/unix/sysv/linux/getsysstats.c @@ -1,5 +1,5 @@ /* Determine various system internal values, Linux version. - Copyright (C) 1996-2003,2006,2007,2009,2010 Free Software Foundation, Inc. + Copyright (C) 1996-2003,2006,2007,2009,2010,2011 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Ulrich Drepper , 1996. @@ -35,6 +35,16 @@ #include #include +#include + +#ifndef HAVE_CLOCK_GETTIME_VSYSCALL +# undef INTERNAL_VSYSCALL +# define INTERNAL_VSYSCALL INTERNAL_SYSCALL +# undef INLINE_VSYSCALL +# define INLINE_VSYSCALL INLINE_SYSCALL +#else +# include +#endif /* How we can determine the number of available processors depends on @@ -128,6 +138,22 @@ next_line (int fd, char *const buffer, char **cp, char **re, int __get_nprocs () { + static int cached_result; + static time_t timestamp; + +#ifdef __ASSUME_POSIX_TIMERS + struct timespec ts; + INTERNAL_SYSCALL_DECL (err); + INTERNAL_VSYSCALL (clock_gettime, err, 2, CLOCK_REALTIME, &ts); +#else + struct timeval ts; + gettimeofday (&ts, NULL); +#endif + time_t prev = timestamp; + atomic_read_barrier (); + if (ts.tv_sec == prev) + return cached_result; + /* XXX Here will come a test for the new system call. */ const size_t buffer_size = __libc_use_alloca (8192) ? 8192 : 512; @@ -169,6 +195,10 @@ __get_nprocs () } } + cached_result = result; + atomic_write_barrier (); + timestamp = ts.tv_sec; + return result; } weak_alias (__get_nprocs, get_nprocs) -- cgit v1.2.1