diff options
Diffstat (limited to 'arch/x86/kernel/tsc_64.c')
| -rw-r--r-- | arch/x86/kernel/tsc_64.c | 100 |
1 files changed, 72 insertions, 28 deletions
diff --git a/arch/x86/kernel/tsc_64.c b/arch/x86/kernel/tsc_64.c index 9c70af45b42b..947554ddabb6 100644 --- a/arch/x86/kernel/tsc_64.c +++ b/arch/x86/kernel/tsc_64.c @@ -10,6 +10,7 @@ #include <asm/hpet.h> #include <asm/timex.h> +#include <asm/timer.h> static int notsc __initdata = 0; @@ -18,19 +19,51 @@ EXPORT_SYMBOL(cpu_khz); unsigned int tsc_khz; EXPORT_SYMBOL(tsc_khz); -static unsigned int cyc2ns_scale __read_mostly; +/* Accelerators for sched_clock() + * convert from cycles(64bits) => nanoseconds (64bits) + * basic equation: + * ns = cycles / (freq / ns_per_sec) + * ns = cycles * (ns_per_sec / freq) + * ns = cycles * (10^9 / (cpu_khz * 10^3)) + * ns = cycles * (10^6 / cpu_khz) + * + * Then we use scaling math (suggested by george@mvista.com) to get: + * ns = cycles * (10^6 * SC / cpu_khz) / SC + * ns = cycles * cyc2ns_scale / SC + * + * 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 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!" + */ +DEFINE_PER_CPU(unsigned long, cyc2ns); -static inline void set_cyc2ns_scale(unsigned long khz) +static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu) { - cyc2ns_scale = (NSEC_PER_MSEC << NS_SCALE) / khz; -} + unsigned long flags, prev_scale, *scale; + unsigned long long tsc_now, ns_now; -static unsigned long long cycles_2_ns(unsigned long long cyc) -{ - return (cyc * cyc2ns_scale) >> NS_SCALE; + local_irq_save(flags); + sched_clock_idle_sleep_event(); + + scale = &per_cpu(cyc2ns, cpu); + + rdtscll(tsc_now); + ns_now = __cycles_2_ns(tsc_now); + + prev_scale = *scale; + if (cpu_khz) + *scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz; + + sched_clock_idle_wakeup_event(0); + local_irq_restore(flags); } -unsigned long long sched_clock(void) +unsigned long long native_sched_clock(void) { unsigned long a = 0; @@ -44,12 +77,27 @@ unsigned long long sched_clock(void) return cycles_2_ns(a); } +/* 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 + + static int tsc_unstable; -inline int check_tsc_unstable(void) +int check_tsc_unstable(void) { return tsc_unstable; } +EXPORT_SYMBOL_GPL(check_tsc_unstable); + #ifdef CONFIG_CPU_FREQ /* Frequency scaling support. Adjust the TSC based timer when the cpu frequency @@ -100,7 +148,9 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, mark_tsc_unstable("cpufreq changes"); } - set_cyc2ns_scale(tsc_khz_ref); + preempt_disable(); + set_cyc2ns_scale(tsc_khz_ref, smp_processor_id()); + preempt_enable(); return 0; } @@ -133,12 +183,12 @@ static unsigned long __init tsc_read_refs(unsigned long *pm, int i; for (i = 0; i < MAX_RETRIES; i++) { - t1 = get_cycles_sync(); + t1 = get_cycles(); if (hpet) *hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF; else *pm = acpi_pm_read_early(); - t2 = get_cycles_sync(); + t2 = get_cycles(); if ((t2 - t1) < SMI_TRESHOLD) return t2; } @@ -151,7 +201,7 @@ static unsigned long __init tsc_read_refs(unsigned long *pm, void __init tsc_calibrate(void) { unsigned long flags, tsc1, tsc2, tr1, tr2, pm1, pm2, hpet1, hpet2; - int hpet = is_hpet_enabled(); + int hpet = is_hpet_enabled(), cpu; local_irq_save(flags); @@ -162,9 +212,9 @@ void __init tsc_calibrate(void) outb(0xb0, 0x43); outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42); outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42); - tr1 = get_cycles_sync(); + tr1 = get_cycles(); while ((inb(0x61) & 0x20) == 0); - tr2 = get_cycles_sync(); + tr2 = get_cycles(); tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL); @@ -206,7 +256,9 @@ void __init tsc_calibrate(void) } tsc_khz = tsc2 / tsc1; - set_cyc2ns_scale(tsc_khz); + + for_each_possible_cpu(cpu) + set_cyc2ns_scale(tsc_khz, cpu); } /* @@ -222,17 +274,9 @@ __cpuinit int unsynchronized_tsc(void) if (apic_is_clustered_box()) return 1; #endif - /* Most intel systems have synchronized TSCs except for - multi node systems */ - if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) { -#ifdef CONFIG_ACPI - /* But TSC doesn't tick in C3 so don't use it there */ - if (acpi_gbl_FADT.header.length > 0 && - acpi_gbl_FADT.C3latency < 1000) - return 1; -#endif + + if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) return 0; - } /* Assume multi socket systems are not synchronized */ return num_present_cpus() > 1; @@ -250,13 +294,13 @@ __setup("notsc", notsc_setup); /* clock source code: */ static cycle_t read_tsc(void) { - cycle_t ret = (cycle_t)get_cycles_sync(); + cycle_t ret = (cycle_t)get_cycles(); return ret; } static cycle_t __vsyscall_fn vread_tsc(void) { - cycle_t ret = (cycle_t)get_cycles_sync(); + cycle_t ret = (cycle_t)vget_cycles(); return ret; } |