Messages in this thread | | | Date | Mon, 10 Feb 2014 19:08:19 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 6/7] perf: Centralise context pmu disabling |
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On Mon, Feb 10, 2014 at 05:44:23PM +0000, Mark Rutland wrote: > Commit 443772776c69 (perf: Disable all pmus on unthrottling and > rescheduling) identified an issue with having multiple PMUs sharing a > perf_event_context, but only partially solved the issue. > > While ctx::pmu will be disabled across all of its events being > scheduled, pmus which are not ctx::pmu will be repeatedly enabled and > disabled between events being added, possibly counting imbetween > pmu::add calls. This could be expensive and could lead to events > counting for differing periods. > > Instead, this patch adds new helpers to disable/enable all pmus which > have events in a context. While perf_pmu_{dis,en}able may be called > repeatedly for a particular pmu, disabling is reference counted such > that the real pmu::{dis,en}able callbacks are only called once (were > this not the case, the current code would be broken for ctx::pmu). > > Uses of perf_pmu{disable,enable}(ctx->pmu) are replaced with > perf_ctx_pmus_{disable,enable}(ctx). The now unnecessary calls to > perf_pmu_enable and perf_pmu_disable added by 443772776c69 are removed.
Hurmn; instead of adding more for_each_event iterations we should be reducing them.
Given that we currently schedule first to last and stop on the first event that fails to schedule, we can terminate the ctx_sched_out() loop when it finds the first event that wasn't actually scheduled.
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