From 91ec87d57fc38c529034e853687dfb7756de5406 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 22 Mar 2012 21:15:51 -0700 Subject: 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 Signed-off-by: John Stultz --- arch/x86/kernel/vsyscall_64.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'arch/x86/kernel/vsyscall_64.c') diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c index cdc95a707cd..4285f1f404c 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); } -- cgit v1.2.3-70-g09d2