diff options
| author |   Andi Kleen <ak@suse.de> | 2006-01-11 22:45:24 +0100 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@g5.osdl.org> | 2006-01-11 19:04:58 -0800 |
| commit | c818a18146997d1356a4840b0c01f1168c16c8a4 (patch) | |
| tree | 8d7e049742e87666bf3089fe46e04828b6417fd7 /include/asm-x86_64/timex.h | |
| parent | [PATCH] x86_64: Support alternative() in vsyscalls (diff) | |
| download | linux-dev-c818a18146997d1356a4840b0c01f1168c16c8a4.tar.xz linux-dev-c818a18146997d1356a4840b0c01f1168c16c8a4.zip | |
[PATCH] x86_64: On Intel CPUs don't do an additional CPU sync before RDTSC
RDTSC serialization using cpuid is not needed for Intel platforms.
This increases gettimeofday performance.
Cc: vojtech@suse.cz
Cc: rohit.seth@intel.com
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/asm-x86_64/timex.h')
| -rw-r--r-- | include/asm-x86_64/timex.h | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/include/asm-x86_64/timex.h b/include/asm-x86_64/timex.h index f971f45d6d78..f18443fcdf04 100644 --- a/include/asm-x86_64/timex.h +++ b/include/asm-x86_64/timex.h @@ -10,6 +10,9 @@ #include <asm/msr.h> #include <asm/vsyscall.h> #include <asm/hpet.h> +#include <asm/system.h> +#include <asm/processor.h> +#include <linux/compiler.h> #define CLOCK_TICK_RATE PIT_TICK_RATE /* Underlying HZ */ @@ -23,6 +26,19 @@ static inline cycles_t get_cycles (void) return ret; } +/* Like get_cycles, but make sure the CPU is synchronized. */ +static __always_inline cycles_t get_cycles_sync(void) +{ + unsigned long long ret; + unsigned eax; + /* Don't do an additional sync on CPUs where we know + RDTSC is already synchronous. */ + alternative_io(ASM_NOP2, "cpuid", X86_FEATURE_SYNC_RDTSC, + "=a" (eax), "0" (1) : "ebx","ecx","edx","memory"); + rdtscll(ret); + return ret; +} + extern unsigned int cpu_khz; extern int read_current_timer(unsigned long *timer_value); |