forked from Minki/linux
perf/cgroups: Don't rotate events for cgroups unnecessarily
Currently perf_rotate_context assumes that if the context's nr_events != nr_active a rotation is necessary for perf event multiplexing. With cgroups, nr_events is the total count of events for all cgroups and nr_active will not include events in a cgroup other than the current task's. This makes rotation appear necessary for cgroups when it is not. Add a perf_event_context flag that is set when rotation is necessary. Clear the flag during sched_out and set it when a flexible sched_in fails due to resources. Signed-off-by: Ian Rogers <irogers@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Kan Liang <kan.liang@linux.intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Link: https://lkml.kernel.org/r/20190601082722.44543-1-irogers@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -749,6 +749,11 @@ struct perf_event_context {
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int nr_stat;
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int nr_freq;
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int rotate_disable;
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/*
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* Set when nr_events != nr_active, except tolerant to events not
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* necessary to be active due to scheduling constraints, such as cgroups.
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*/
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int rotate_necessary;
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refcount_t refcount;
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struct task_struct *task;
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@ -2952,6 +2952,12 @@ static void ctx_sched_out(struct perf_event_context *ctx,
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if (!ctx->nr_active || !(is_active & EVENT_ALL))
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return;
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/*
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* If we had been multiplexing, no rotations are necessary, now no events
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* are active.
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*/
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ctx->rotate_necessary = 0;
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perf_pmu_disable(ctx->pmu);
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if (is_active & EVENT_PINNED) {
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list_for_each_entry_safe(event, tmp, &ctx->pinned_active, active_list)
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@ -3319,10 +3325,13 @@ static int flexible_sched_in(struct perf_event *event, void *data)
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return 0;
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if (group_can_go_on(event, sid->cpuctx, sid->can_add_hw)) {
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if (!group_sched_in(event, sid->cpuctx, sid->ctx))
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list_add_tail(&event->active_list, &sid->ctx->flexible_active);
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else
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int ret = group_sched_in(event, sid->cpuctx, sid->ctx);
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if (ret) {
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sid->can_add_hw = 0;
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sid->ctx->rotate_necessary = 1;
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return 0;
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}
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list_add_tail(&event->active_list, &sid->ctx->flexible_active);
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}
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return 0;
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@ -3690,24 +3699,17 @@ ctx_first_active(struct perf_event_context *ctx)
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static bool perf_rotate_context(struct perf_cpu_context *cpuctx)
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{
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struct perf_event *cpu_event = NULL, *task_event = NULL;
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bool cpu_rotate = false, task_rotate = false;
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struct perf_event_context *ctx = NULL;
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struct perf_event_context *task_ctx = NULL;
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int cpu_rotate, task_rotate;
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/*
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* Since we run this from IRQ context, nobody can install new
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* events, thus the event count values are stable.
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*/
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if (cpuctx->ctx.nr_events) {
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if (cpuctx->ctx.nr_events != cpuctx->ctx.nr_active)
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cpu_rotate = true;
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}
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ctx = cpuctx->task_ctx;
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if (ctx && ctx->nr_events) {
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if (ctx->nr_events != ctx->nr_active)
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task_rotate = true;
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}
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cpu_rotate = cpuctx->ctx.rotate_necessary;
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task_ctx = cpuctx->task_ctx;
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task_rotate = task_ctx ? task_ctx->rotate_necessary : 0;
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if (!(cpu_rotate || task_rotate))
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return false;
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@ -3716,7 +3718,7 @@ static bool perf_rotate_context(struct perf_cpu_context *cpuctx)
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perf_pmu_disable(cpuctx->ctx.pmu);
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if (task_rotate)
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task_event = ctx_first_active(ctx);
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task_event = ctx_first_active(task_ctx);
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if (cpu_rotate)
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cpu_event = ctx_first_active(&cpuctx->ctx);
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@ -3724,17 +3726,17 @@ static bool perf_rotate_context(struct perf_cpu_context *cpuctx)
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* As per the order given at ctx_resched() first 'pop' task flexible
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* and then, if needed CPU flexible.
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*/
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if (task_event || (ctx && cpu_event))
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ctx_sched_out(ctx, cpuctx, EVENT_FLEXIBLE);
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if (task_event || (task_ctx && cpu_event))
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ctx_sched_out(task_ctx, cpuctx, EVENT_FLEXIBLE);
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if (cpu_event)
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cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
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if (task_event)
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rotate_ctx(ctx, task_event);
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rotate_ctx(task_ctx, task_event);
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if (cpu_event)
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rotate_ctx(&cpuctx->ctx, cpu_event);
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perf_event_sched_in(cpuctx, ctx, current);
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perf_event_sched_in(cpuctx, task_ctx, current);
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perf_pmu_enable(cpuctx->ctx.pmu);
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perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
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