r15508: Use clock_gettime for profiling timstamps if it is available. Use

the fastest clock available on uniprocessors.

1 files changed, 21 insertions, 0 deletions

diff --git a/source/profile/profile.c b/source/profile/profile.c
index db8a643042b..bacf00eb017 100644
--- a/source/profile/profile.c
+++ b/source/profile/profile.c
@@ -28,6 +28,9 @@
 #ifdef WITH_PROFILE
 static int shm_id;
 static BOOL read_only;
+#if defined(HAVE_CLOCK_GETTIME)
+clockid_t __profile_clock;
+#endif
 #endif
 
 struct profile_header *profile_h;
@@ -103,6 +106,24 @@ BOOL profile_setup(BOOL rdonly)
 
 	read_only = rdonly;
 
+#if defined(HAVE_CLOCK_GETTIME)
+	if (this_is_smp()) {
+		/* This is faster that gettimeofday, but not fast enough to
+		 * leave it enabled in production.
+		 */
+		__profile_clock = CLOCK_MONOTONIC;
+	} else {
+		/* CLOCK_PROCESS_CPUTIME_ID is sufficiently fast that the
+		 * always profiling times is plausible. Unfortunately it is
+		 * only accurate if we can guarantee we will not be scheduled
+		 * onto a different CPU between samples. Until there is some
+		 * way to set processor affinity, we can only use this on
+		 * uniprocessors.
+		 */
+		__profile_clock = CLOCK_PROCESS_CPUTIME_ID;
+	}
+#endif
+
  again:
 	/* try to use an existing key */
 	shm_id = shmget(PROF_SHMEM_KEY, 0, 0);