diff options
| author |   Guillaume Chazarain <guichaz@yahoo.fr> | 2008-01-30 13:30:06 +0100 |
|---|---|---|
| committer |   Ingo Molnar <mingo@elte.hu> | 2008-01-30 13:30:06 +0100 |
| commit | 53d517cdbaac704352b3d0c10fecb99e0b54572e (patch) | |
| tree | 4056bc99a4e6077d7d968d30ea21895e425a83ef /include | |
| parent | x86: protect against sigaltstack wraparound (diff) | |
| download | linux-dev-53d517cdbaac704352b3d0c10fecb99e0b54572e.tar.xz linux-dev-53d517cdbaac704352b3d0c10fecb99e0b54572e.zip | |
x86: scale cyc_2_nsec according to CPU frequency
scale the sched_clock() cyc_2_nsec scaling factor according to
CPU frequency changes.
[ mingo@elte.hu: simplified it and fixed it for SMP. ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include')
| -rw-r--r-- | include/asm-x86/timer.h | 23 |
1 files changed, 18 insertions, 5 deletions
diff --git a/include/asm-x86/timer.h b/include/asm-x86/timer.h index 0db7e994fb8b..4f6fcb050c11 100644 --- a/include/asm-x86/timer.h +++ b/include/asm-x86/timer.h @@ -2,6 +2,7 @@ #define _ASMi386_TIMER_H #include <linux/init.h> #include <linux/pm.h> +#include <linux/percpu.h> #define TICK_SIZE (tick_nsec / 1000) @@ -16,7 +17,7 @@ extern int recalibrate_cpu_khz(void); #define calculate_cpu_khz() native_calculate_cpu_khz() #endif -/* Accellerators for sched_clock() +/* Accelerators for sched_clock() * convert from cycles(64bits) => nanoseconds (64bits) * basic equation: * ns = cycles / (freq / ns_per_sec) @@ -31,20 +32,32 @@ extern int recalibrate_cpu_khz(void); * And since SC is a constant power of two, we can convert the div * into a shift. * - * We can use khz divisor instead of mhz to keep a better percision, since + * We can use khz divisor instead of mhz to keep a better precision, since * cyc2ns_scale is limited to 10^6 * 2^10, which fits in 32 bits. * (mathieu.desnoyers@polymtl.ca) * * -johnstul@us.ibm.com "math is hard, lets go shopping!" */ -extern unsigned long cyc2ns_scale __read_mostly; + +DECLARE_PER_CPU(unsigned long, cyc2ns); #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ -static inline unsigned long long cycles_2_ns(unsigned long long cyc) +static inline unsigned long long __cycles_2_ns(unsigned long long cyc) { - return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR; + return cyc * per_cpu(cyc2ns, smp_processor_id()) >> CYC2NS_SCALE_FACTOR; } +static inline unsigned long long cycles_2_ns(unsigned long long cyc) +{ + unsigned long long ns; + unsigned long flags; + + local_irq_save(flags); + ns = __cycles_2_ns(cyc); + local_irq_restore(flags); + + return ns; +} #endif |