The patch titled sched_clock: fix calculation of other CPU has been added to the -mm tree. Its filename is sched_clock-fix-calculation-of-other-cpu.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://www.zip.com.au/~akpm/linux/patches/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: sched_clock: fix calculation of other CPU From: Steven Rostedt <rostedt@xxxxxxxxxxx> The algorithm to calculate the 'now' of another CPU is not correct. At each scheduler tick, each CPU records the last sched_clock and gtod (tick_raw and tick_gtod respectively). If the TSC is somewhat the same in speed between two clocks the algorithm would be: tick_gtod1 + (now1 - tick_raw1) = tick_gtod2 + (now2 - tick_raw2) To calculate now2 we would have: now2 = (tick_gtod1 - tick_gtod2) + (tick_raw2 - tick_raw1) + now1 Currently the algorithm is: now2 = (tick_gtod1 - tick_gtod2) + (tick_raw1 - tick_raw2) + now1 This solves most of the rest of the issues I've had with timestamps in ftace. Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: john stultz <johnstul@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/sched_clock.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff -puN kernel/sched_clock.c~sched_clock-fix-calculation-of-other-cpu kernel/sched_clock.c --- a/kernel/sched_clock.c~sched_clock-fix-calculation-of-other-cpu +++ a/kernel/sched_clock.c @@ -160,8 +160,8 @@ u64 sched_clock_cpu(int cpu) now -= my_scd->tick_raw; now += scd->tick_raw; - now -= my_scd->tick_gtod; - now += scd->tick_gtod; + now += my_scd->tick_gtod; + now -= scd->tick_gtod; __raw_spin_unlock(&my_scd->lock); } else { _ Patches currently in -mm which might be from rostedt@xxxxxxxxxxx are origin.patch linux-next.patch sched_clock-fix-calculation-of-other-cpu.patch ftrace-disable-function-tracing-bringing-up-new-cpu.patch split-the-typecheck-macros-out-of-include-linux-kernelh.patch locking-add-typecheck-on-irqsave-and-friends-for-correct-flags.patch locking-add-typecheck-on-irqsave-and-friends-for-correct-flags-fix.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