diff options
author | Andy Lutomirski <luto@mit.edu> | 2012-03-23 08:15:51 +0400 |
---|---|---|
committer | John Stultz <john.stultz@linaro.org> | 2012-03-24 03:49:33 +0400 |
commit | 91ec87d57fc38c529034e853687dfb7756de5406 (patch) | |
tree | 4f88d6a7e0221bdd791a1de6d4c36b17da8337a2 /arch/x86/vdso/vclock_gettime.c | |
parent | 88b28adf6fcdd6d10a1cfc7765bb200d7366a265 (diff) | |
download | linux-91ec87d57fc38c529034e853687dfb7756de5406.tar.xz |
x86-64: Simplify and optimize vdso clock_gettime monotonic variants
We used to store the wall-to-monotonic offset and the realtime base.
It's faster to precompute the monotonic base.
This is about a 3% speedup on Sandy Bridge for CLOCK_MONOTONIC.
It's much more impressive for CLOCK_MONOTONIC_COARSE.
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Diffstat (limited to 'arch/x86/vdso/vclock_gettime.c')
-rw-r--r-- | arch/x86/vdso/vclock_gettime.c | 38 |
1 files changed, 8 insertions, 30 deletions
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c index 944c5e5d6b6a..6eea70b8f384 100644 --- a/arch/x86/vdso/vclock_gettime.c +++ b/arch/x86/vdso/vclock_gettime.c @@ -113,27 +113,17 @@ notrace static noinline int do_realtime(struct timespec *ts) notrace static noinline int do_monotonic(struct timespec *ts) { - unsigned long seq, ns, secs; + unsigned long seq, ns; int mode; do { seq = read_seqcount_begin(>od->seq); mode = gtod->clock.vclock_mode; - secs = gtod->wall_time_sec; - ns = gtod->wall_time_nsec + vgetns(); - secs += gtod->wall_to_monotonic.tv_sec; - ns += gtod->wall_to_monotonic.tv_nsec; + ts->tv_sec = gtod->monotonic_time_sec; + ts->tv_nsec = gtod->monotonic_time_nsec; + ns = vgetns(); } while (unlikely(read_seqcount_retry(>od->seq, seq))); - - /* wall_time_nsec, vgetns(), and wall_to_monotonic.tv_nsec - * are all guaranteed to be nonnegative. - */ - while (ns >= NSEC_PER_SEC) { - ns -= NSEC_PER_SEC; - ++secs; - } - ts->tv_sec = secs; - ts->tv_nsec = ns; + timespec_add_ns(ts, ns); return mode; } @@ -151,25 +141,13 @@ notrace static noinline int do_realtime_coarse(struct timespec *ts) notrace static noinline int do_monotonic_coarse(struct timespec *ts) { - unsigned long seq, ns, secs; + unsigned long seq; do { seq = read_seqcount_begin(>od->seq); - secs = gtod->wall_time_coarse.tv_sec; - ns = gtod->wall_time_coarse.tv_nsec; - secs += gtod->wall_to_monotonic.tv_sec; - ns += gtod->wall_to_monotonic.tv_nsec; + ts->tv_sec = gtod->monotonic_time_coarse.tv_sec; + ts->tv_nsec = gtod->monotonic_time_coarse.tv_nsec; } while (unlikely(read_seqcount_retry(>od->seq, seq))); - /* wall_time_nsec and wall_to_monotonic.tv_nsec are - * guaranteed to be between 0 and NSEC_PER_SEC. - */ - if (ns >= NSEC_PER_SEC) { - ns -= NSEC_PER_SEC; - ++secs; - } - ts->tv_sec = secs; - ts->tv_nsec = ns; - return 0; } |