diff options
Diffstat (limited to 'arch/i386/kernel/tsc.c')
| -rw-r--r-- | arch/i386/kernel/tsc.c | 32 |
1 files changed, 23 insertions, 9 deletions
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c index f64b81f3033..252f9010f28 100644 --- a/arch/i386/kernel/tsc.c +++ b/arch/i386/kernel/tsc.c @@ -4,6 +4,7 @@ * See comments there for proper credits. */ +#include <linux/sched.h> #include <linux/clocksource.h> #include <linux/workqueue.h> #include <linux/cpufreq.h> @@ -83,7 +84,7 @@ static inline int check_tsc_unstable(void) * * -johnstul@us.ibm.com "math is hard, lets go shopping!" */ -static unsigned long cyc2ns_scale __read_mostly; +unsigned long cyc2ns_scale __read_mostly; #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ @@ -92,32 +93,44 @@ static inline void set_cyc2ns_scale(unsigned long cpu_khz) cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz; } -static inline unsigned long long cycles_2_ns(unsigned long long cyc) -{ - return (cyc * cyc2ns_scale) >> CYC2NS_SCALE_FACTOR; -} - /* * Scheduler clock - returns current time in nanosec units. */ -unsigned long long sched_clock(void) +unsigned long long native_sched_clock(void) { unsigned long long this_offset; /* * Fall back to jiffies if there's no TSC available: + * ( But note that we still use it if the TSC is marked + * unstable. We do this because unlike Time Of Day, + * the scheduler clock tolerates small errors and it's + * very important for it to be as fast as the platform + * can achive it. ) */ - if (unlikely(!tsc_enabled)) + if (unlikely(!tsc_enabled && !tsc_unstable)) /* No locking but a rare wrong value is not a big deal: */ return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ); /* read the Time Stamp Counter: */ - get_scheduled_cycles(this_offset); + rdtscll(this_offset); /* return the value in ns */ return cycles_2_ns(this_offset); } +/* We need to define a real function for sched_clock, to override the + weak default version */ +#ifdef CONFIG_PARAVIRT +unsigned long long sched_clock(void) +{ + return paravirt_sched_clock(); +} +#else +unsigned long long sched_clock(void) + __attribute__((alias("native_sched_clock"))); +#endif + unsigned long native_calculate_cpu_khz(void) { unsigned long long start, end; @@ -277,6 +290,7 @@ static struct clocksource clocksource_tsc = { void mark_tsc_unstable(char *reason) { + sched_clock_unstable_event(); if (!tsc_unstable) { tsc_unstable = 1; tsc_enabled = 0; |