Messages in this thread | | | From | Song Liu <> | Subject | Re: [PATCH v8] perf: Sharing PMU counters across compatible events | Date | Thu, 12 Dec 2019 16:00:24 +0000 |
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> On Dec 12, 2019, at 7:45 AM, Song Liu <songliubraving@fb.com> wrote: > > > >> On Dec 12, 2019, at 7:39 AM, Peter Zijlstra <peterz@infradead.org> wrote: >> >> On Fri, Dec 06, 2019 at 04:24:47PM -0800, Song Liu wrote: >> >>> @@ -2174,6 +2410,14 @@ __perf_remove_from_context(struct perf_event *event, >>> update_cgrp_time_from_cpuctx(cpuctx); >>> } >>> >>> + if (event->dup_master == event) { >>> + if (ctx->is_active) >>> + ctx_resched(cpuctx, cpuctx->task_ctx, >>> + get_event_type(event), NULL, event); >>> + else >>> + perf_event_remove_dup(event, ctx); >>> + } >>> + >>> event_sched_out(event, cpuctx, ctx); >>> if (flags & DETACH_GROUP) >>> perf_group_detach(event); >>> @@ -2241,6 +2485,14 @@ static void __perf_event_disable(struct perf_event *event, >>> update_cgrp_time_from_event(event); >>> } >>> >>> + if (event->dup_master == event) { >>> + if (ctx->is_active) >>> + ctx_resched(cpuctx, cpuctx->task_ctx, >>> + get_event_type(event), NULL, event); >>> + else >>> + perf_event_remove_dup(event, ctx); >>> + } >>> + >>> if (event == event->group_leader) >>> group_sched_out(event, cpuctx, ctx); >>> else >> >>> @@ -2544,7 +2793,9 @@ static void perf_event_sched_in(struct perf_cpu_context *cpuctx, >>> */ >>> static void ctx_resched(struct perf_cpu_context *cpuctx, >>> struct perf_event_context *task_ctx, >>> - enum event_type_t event_type) >>> + enum event_type_t event_type, >>> + struct perf_event *event_add_dup, >>> + struct perf_event *event_del_dup) >>> { >>> enum event_type_t ctx_event_type; >>> bool cpu_event = !!(event_type & EVENT_CPU); >>> @@ -2574,6 +2825,18 @@ static void ctx_resched(struct perf_cpu_context *cpuctx, >>> else if (ctx_event_type & EVENT_PINNED) >>> cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE); >>> >>> + if (event_add_dup) { >>> + if (event_add_dup->ctx->is_active) >>> + ctx_sched_out(event_add_dup->ctx, cpuctx, EVENT_ALL); >>> + perf_event_setup_dup(event_add_dup, event_add_dup->ctx); >>> + } >>> + >>> + if (event_del_dup) { >>> + if (event_del_dup->ctx->is_active) >>> + ctx_sched_out(event_del_dup->ctx, cpuctx, EVENT_ALL); >>> + perf_event_remove_dup(event_del_dup, event_del_dup->ctx); >>> + } >>> + >>> perf_event_sched_in(cpuctx, task_ctx, current); >>> perf_pmu_enable(cpuctx->ctx.pmu); >>> } >> >> Yuck! >> >> Why do you do a full reschedule when you take out a master? > > If there is active slave using this master, we need to schedule out > them before removing the master. > > We can improve the check though. We only need to do it if the master > is in state PERF_EVENT_STATE_ENABLED. > > Or we can add a different function to only schedule out slaves.
It is tricky to only schedule out slaves, because the slave could be in a group. If we don't reschedule all events, we need to make sure that "swapping master" always succeed.
Song
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