The patch titled x86: fix cpufreq tsc scaling has been added to the -mm tree. Its filename is x86-fix-cpufreq-tsc-scaling.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: x86: fix cpufreq tsc scaling From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> For freqency dependent TSCs we only scale the cycles, we do not account for the discrepancy in absolute value. Add a constant factor so that: c1 + f1*cyc == c2 + f2*cyc LKML-Reference: <new-submission> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Chucked-on-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/x86/include/asm/timer.h | 6 +++++- arch/x86/kernel/tsc.c | 8 ++++++-- 2 files changed, 11 insertions(+), 3 deletions(-) diff -puN arch/x86/include/asm/timer.h~x86-fix-cpufreq-tsc-scaling arch/x86/include/asm/timer.h --- a/arch/x86/include/asm/timer.h~x86-fix-cpufreq-tsc-scaling +++ a/arch/x86/include/asm/timer.h @@ -45,12 +45,16 @@ extern int no_timer_check; */ DECLARE_PER_CPU(unsigned long, cyc2ns); +DECLARE_PER_CPU(unsigned long long, cyc2ns_offset); #define CYC2NS_SCALE_FACTOR 10 /* 2^10, carefully chosen */ static inline unsigned long long __cycles_2_ns(unsigned long long cyc) { - return cyc * per_cpu(cyc2ns, smp_processor_id()) >> CYC2NS_SCALE_FACTOR; + int cpu = smp_processor_id(); + unsigned long long ns = per_cpu(cyc2ns_offset, cpu); + ns += cyc * per_cpu(cyc2ns, cpu) >> CYC2NS_SCALE_FACTOR; + return ns; } static inline unsigned long long cycles_2_ns(unsigned long long cyc) diff -puN arch/x86/kernel/tsc.c~x86-fix-cpufreq-tsc-scaling arch/x86/kernel/tsc.c --- a/arch/x86/kernel/tsc.c~x86-fix-cpufreq-tsc-scaling +++ a/arch/x86/kernel/tsc.c @@ -590,22 +590,26 @@ EXPORT_SYMBOL(recalibrate_cpu_khz); */ DEFINE_PER_CPU(unsigned long, cyc2ns); +DEFINE_PER_CPU(unsigned long long, cyc2ns_offset); static void set_cyc2ns_scale(unsigned long cpu_khz, int cpu) { - unsigned long long tsc_now, ns_now; + unsigned long long tsc_now, ns_now, *offset; unsigned long flags, *scale; local_irq_save(flags); sched_clock_idle_sleep_event(); scale = &per_cpu(cyc2ns, cpu); + offset = &per_cpu(cyc2ns_offset, cpu); rdtscll(tsc_now); ns_now = __cycles_2_ns(tsc_now); - if (cpu_khz) + if (cpu_khz) { *scale = (NSEC_PER_MSEC << CYC2NS_SCALE_FACTOR)/cpu_khz; + *offset = ns_now - (tsc_now * *scale >> CYC2NS_SCALE_FACTOR); + } sched_clock_idle_wakeup_event(0); local_irq_restore(flags); _ Patches currently in -mm which might be from peterz@xxxxxxxxxxxxx are linux-next.patch x86-fix-cpufreq-tsc-scaling.patch vmscan-evict-use-once-pages-first-v3.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html