Messages in this thread | | | Subject | Re: [RFC 1/2] perf/core: Enable sched_task callbacks if PMU has it | From | "Liang, Kan" <> | Date | Fri, 6 Nov 2020 11:11:55 -0500 |
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On 11/5/2020 7:53 PM, Namhyung Kim wrote: > On Fri, Nov 6, 2020 at 4:01 AM Liang, Kan<kan.liang@linux.intel.com> wrote: >> >> >> On 11/5/2020 10:45 AM, Namhyung Kim wrote: >>> Hello, >>> >>> On Thu, Nov 5, 2020 at 11:47 PM Liang, Kan<kan.liang@linux.intel.com> wrote: >>>> >>>> >>>> On 11/2/2020 9:52 AM, Namhyung Kim wrote: >>>>> If an event associated with a PMU which has a sched_task callback, >>>>> it should be called regardless of cpu/task context. For example, >>>> >>>> I don't think it's necessary. We should call it when we have to. >>>> Otherwise, it just waste cycles. >>>> Shouldn't the patch 2 be enough? >>> I'm not sure, without this patch __perf_event_task_sched_in/out >>> cannot be called for per-cpu events (w/o cgroups) IMHO. >>> And I could not find any other place to check the >>> perf_sched_cb_usages. >>> >> Yes, it should a bug for large PEBS, and it should has always been there >> since the large PEBS was introduced. I just tried some older kernels >> (before recent change). Large PEBS is not flushed with per-cpu events. >> >> But from your description, it looks like the issue is only found after >> recent change. Could you please double check if the issue can also be >> reproduced before the recent change? > Yep, actually Gabriel reported this problem on v4.4 kernel.
Thanks for the confirm.
So large PEBS never works with per-cpu events. :( I will send a new patch set to address the issue.
Thanks, Kan
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