lkml.org 
[lkml]   [2012]   [Feb]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    SubjectRe: [PATCH] perf: fix assertion failure in x86_pmu_start()
    From
    On Tue, Feb 7, 2012 at 11:49 AM, Ingo Molnar <mingo@elte.hu> wrote:
    >
    > * Stephane Eranian <eranian@google.com> wrote:
    >
    >> On Tue, Feb 7, 2012 at 11:25 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
    >> > Le mardi 07 février 2012 à 09:41 +0100, Ingo Molnar a écrit :
    >> >
    >> >> Were these messages introduced by:
    >> >>
    >> >>  e050e3f0a71b: perf: Fix broken interrupt rate throttling
    >> >>
    >> >> as well?
    >> >>
    >> >> In any case I'm holding off on applying the patch before this is
    >> >> resolved.
    >> >
    >> > Reverting e050e3f0a71b solves all my problems, no more warnings.
    >> >
    >> > $ perf record -a -g hackbench 10 thread 4000
    >> > Running with 10*40 (== 400) tasks.
    >> > Time: 13.181
    >> > [ perf record: Woken up 59 times to write data ]
    >> > [ perf record: Captured and wrote 16.874 MB perf.data (~737228 samples)
    >> > ]
    >> >
    >> > $ perf record -a -g hackbench 10 thread 4000
    >> > Running with 10*40 (== 400) tasks.
    >> > Time: 13.124
    >> > [ perf record: Woken up 61 times to write data ]
    >> > [ perf record: Captured and wrote 16.533 MB perf.data (~722349 samples)
    >> > ]
    >> >
    >>
    >> What system is this running on?
    >> The problem is that without e050e3f0a71b interrupt throttling does not work.
    >
    > Fixes are not supposed to regress, so if we cannot resolve this
    > within a couple of days we'll have to revert e050e3f0a71b and
    > re-try it later.
    >
    I suspect in the case of Eric's system, the fact that we do not
    stop the PMU when adjusting frequency anymore may expose a side-effect
    of his BIOS "sharing" the PMU with perf_events. But the config value reported
    by the kernel does not include the INT bit, i.e., the counter does not generate
    interrupts on overflow, so it should not conflict.

    >> I think the key difference is that without the patch,
    >> frequency adjustment happens with the PMU completely stopped
    >> whereas with my patch it does not. I suspect this may be the
    >> issue. I can rework the patch to disable the PMU completely
    >> while retaining the same workflow.
    >
    > Would be nice to try that.
    >
    > Thanks,
    >
    >        Ingo
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2012-02-07 12:09    [W:0.026 / U:60.364 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site