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x86-64: Simplify and optimize vdso clock_gettime monotonic variants

Telusuri Sumber 
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>
This commit is contained in:
Andy Lutomirski
2012-03-22 21:15:51 -07:00
committed by John Stultz
orang tua 88b28adf6f
melakukan 91ec87d57f
3 mengubah file dengan 26 tambahan dan 37 penghapusan
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10
arch/x86/kernel/vsyscall_64.c
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@@ -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);
}