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| author | Andy Lutomirski <luto@mit.edu> | 2012-03-23 04:15:51 (GMT) |
|---|---|---|
| committer | John Stultz <john.stultz@linaro.org> | 2012-03-23 23:49:33 (GMT) |
| commit | 91ec87d57fc38c529034e853687dfb7756de5406 (patch) | |
| tree | 4f88d6a7e0221bdd791a1de6d4c36b17da8337a2 /arch/x86/kernel/vsyscall_64.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/kernel/vsyscall_64.c')
| -rw-r--r-- | arch/x86/kernel/vsyscall_64.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c index cdc95a7..4285f1f 100644 --- a/arch/x86/kernel/vsyscall_64.c +++ b/arch/x86/kernel/vsyscall_64.c @@ -84,6 +84,7 @@ void update_vsyscall(struct timespec *wall_time, struct timespec *wtm, struct clocksource *clock, u32 mult) { write_seqcount_begin(&vsyscall_gtod_data.seq); + struct timespec monotonic; /* copy vsyscall data */ vsyscall_gtod_data.clock.vclock_mode = clock->archdata.vclock_mode; @@ -91,10 +92,17 @@ void update_vsyscall(struct timespec *wall_time, struct timespec *wtm, vsyscall_gtod_data.clock.mask = clock->mask; vsyscall_gtod_data.clock.mult = mult; vsyscall_gtod_data.clock.shift = clock->shift; + vsyscall_gtod_data.wall_time_sec = wall_time->tv_sec; vsyscall_gtod_data.wall_time_nsec = wall_time->tv_nsec; - vsyscall_gtod_data.wall_to_monotonic = *wtm; + + monotonic = timespec_add(*wall_time, *wtm); + vsyscall_gtod_data.monotonic_time_sec = monotonic.tv_sec; + vsyscall_gtod_data.monotonic_time_nsec = monotonic.tv_nsec; + vsyscall_gtod_data.wall_time_coarse = __current_kernel_time(); + vsyscall_gtod_data.monotonic_time_coarse = + timespec_add(vsyscall_gtod_data.wall_time_coarse, *wtm); write_seqcount_end(&vsyscall_gtod_data.seq); } |