From f20bf6125605acbbc7eb8c9420d7221c91aa83eb Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 16 Oct 2007 16:09:20 +0200 Subject: time: introduce xtime_seconds improve performance of sys_time(). sys_time() returns time in seconds, but it does so by calling do_gettimeofday() and then returning the tv_sec portion of the GTOD time. But the data structure "xtime", which is updated by every timer/scheduler tick, already offers HZ granularity time. the patch improves the sysbench oltp macrobenchmark by 4-5% on an AMD dual-core system: v2.6.23: #threads 1: transactions: 4073 (407.23 per sec.) 2: transactions: 8530 (852.81 per sec.) 3: transactions: 8321 (831.88 per sec.) 4: transactions: 8407 (840.58 per sec.) 5: transactions: 8070 (806.74 per sec.) v2.6.23 + sys_time-speedup.patch: 1: transactions: 4281 (428.09 per sec.) 2: transactions: 8910 (890.85 per sec.) 3: transactions: 8659 (865.79 per sec.) 4: transactions: 8676 (867.34 per sec.) 5: transactions: 8532 (852.91 per sec.) and by 4-5% on an Intel dual-core system too: 2.6.23: 1: transactions: 4560 (455.94 per sec.) 2: transactions: 10094 (1009.30 per sec.) 3: transactions: 9755 (975.36 per sec.) 4: transactions: 9859 (985.78 per sec.) 5: transactions: 9701 (969.72 per sec.) 2.6.23 + sys_time-speedup.patch: 1: transactions: 4779 (477.84 per sec.) 2: transactions: 10103 (1010.14 per sec.) 3: transactions: 10141 (1013.93 per sec.) 4: transactions: 10371 (1036.89 per sec.) 5: transactions: 10178 (1017.50 per sec.) (the more CPUs the system has, the more speedup this patch gives for this particular workload.) Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner Signed-off-by: Linus Torvalds --- kernel/time/timekeeping.c | 7 ------- 1 file changed, 7 deletions(-) (limited to 'kernel/time') diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 4ad79f6bdec..7e8983aecf8 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -49,19 +49,12 @@ struct timespec wall_to_monotonic __attribute__ ((aligned (16))); static unsigned long total_sleep_time; /* seconds */ EXPORT_SYMBOL(xtime); - -#ifdef CONFIG_NO_HZ static struct timespec xtime_cache __attribute__ ((aligned (16))); static inline void update_xtime_cache(u64 nsec) { xtime_cache = xtime; timespec_add_ns(&xtime_cache, nsec); } -#else -#define xtime_cache xtime -/* We do *not* want to evaluate the argument for this case */ -#define update_xtime_cache(n) do { } while (0) -#endif static struct clocksource *clock; /* pointer to current clocksource */ -- cgit v1.2.3-18-g5258