Messages in this thread | | | From | Song Liu <> | Subject | Re: [PATCH v8] perf: Sharing PMU counters across compatible events | Date | Thu, 12 Dec 2019 18:01:41 +0000 |
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Hi Peter,
> On Dec 12, 2019, at 8:00 AM, Song Liu <songliubraving@fb.com> wrote: > > > >> 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.
What would you suggest for this one? Maybe we can keep this as-is and optimize later?
Thanks, Song
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