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 /arch/x86/kernel/tsc_32.c | |
| parent | 83bd01024b1fdfc41d9b758e5669e80fca72df66 (diff) | |
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 'arch/x86/kernel/tsc_32.c')
| -rw-r--r-- | arch/x86/kernel/tsc_32.c | 43 |
1 files changed, 37 insertions, 6 deletions
diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c index 9ebc0dab66b..00bb4c1c059 100644 --- a/arch/x86/kernel/tsc_32.c +++ b/arch/x86/kernel/tsc_32.c @@ -5,6 +5,7 @@ #include <linux/jiffies.h> #include <linux/init.h> #include <linux/dmi.h> +#include <linux/percpu.h> #include <asm/delay.h> #include <asm/tsc.h> @@ -80,13 +81,31 @@ EXPORT_SYMBOL_GPL(check_tsc_unstable); * * -johnstul@us.ibm.com "math is hard, lets go shopping!" */ -unsigned long cyc2ns_scale __read_mostly; -#define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ +DEFINE_PER_CPU(unsigned long, cyc2ns); -static inline void set_cyc2ns_scale(unsigned long cpu_khz) +static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu) { - cyc2ns_scale = (1000000 << CYC2NS_SCALE_FACTOR)/cpu_khz; + unsigned long flags, prev_scale, *scale; + unsigned long long tsc_now, ns_now; + + 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; + + /* + * Start smoothly with the new frequency: + */ + sched_clock_idle_wakeup_event(0); + local_irq_restore(flags); } /* @@ -239,7 +258,9 @@ time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, void *data) ref_freq, freq->new); if (!(freq->flags & CPUFREQ_CONST_LOOPS)) { tsc_khz = cpu_khz; - set_cyc2ns_scale(cpu_khz); + preempt_disable(); + set_cyc2ns_scale(cpu_khz, smp_processor_id()); + preempt_enable(); /* * TSC based sched_clock turns * to junk w/ cpufreq @@ -367,6 +388,8 @@ static inline void check_geode_tsc_reliable(void) { } void __init tsc_init(void) { + int cpu; + if (!cpu_has_tsc || tsc_disable) goto out_no_tsc; @@ -380,7 +403,15 @@ void __init tsc_init(void) (unsigned long)cpu_khz / 1000, (unsigned long)cpu_khz % 1000); - set_cyc2ns_scale(cpu_khz); + /* + * Secondary CPUs do not run through tsc_init(), so set up + * all the scale factors for all CPUs, assuming the same + * speed as the bootup CPU. (cpufreq notifiers will fix this + * up if their speed diverges) + */ + for_each_possible_cpu(cpu) + set_cyc2ns_scale(cpu_khz, cpu); + use_tsc_delay(); /* Check and install the TSC clocksource */ |