Messages in this thread | | | Date | Thu, 25 Aug 2011 16:36:42 +0200 | Subject | Re: [PATCH] perf_event: fix slow and broken cgroup context switch code | From | Stephane Eranian <> |
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On Thu, Aug 25, 2011 at 4:20 PM, Peter Zijlstra <peterz@infradead.org> wrote: > On Thu, 2011-08-25 at 15:58 +0200, Stephane Eranian wrote: >> +static inline void perf_event_task_sched_out(struct task_struct >> *prev, >> + struct task_struct *next) >> { >> perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, NULL, 0); >> >> - __perf_event_task_sched_out(task, next); >> + if (static_branch(&perf_sched_events)) >> + __perf_event_task_sched_out(prev, next); >> } > > Right, so the reason we removed the static branch from there is > > lkml.kernel.org/r/20110324164436.GC1930@jolsa.brq.redhat.com > > now I think the series 075e0b0085 to 64ce312618e should have cured that > problem, and adding the static_branch() is now safe again. But there's > no mention of any of this in the Changelog. > I realized I did not talk about the static_branch() change after I had clicked on Send. But to me, this looks natural to have the static branch in the ctxsw out routine. This has to be symmetrical with ctxsw in . The static branch is about avoiding perf ctxsw when there is no need for it, i.e., no per-thread nor per-cgroup events. -- 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/
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