From df6c3db8d30fb1699ccbc403196b86324f4257af Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Wed, 19 Jul 2017 09:52:47 +0200 Subject: [PATCH] perf/x86/intel: Add proper condition to run sched_task callbacks We have 2 functions using the same sched_task callback: - PEBS drain for free running counters - LBR save/store Both of them are called from intel_pmu_sched_task() and either of them can be unwillingly triggered when the other one is configured to run. Let's say there's PEBS drain configured in sched_task callback for the event, but in the callback itself (intel_pmu_sched_task()) we will also run the code for LBR save/restore, which we did not ask for, but the code in intel_pmu_sched_task() does not check for that. This can lead to extra cycles in some perf monitoring, like when we monitor PEBS event without LBR data. # perf record --no-timestamp -c 10000 -e cycles:p ./perf bench sched pipe -l 1000000 (We need PEBS, non freq/non timestamp event to enable the sched_task callback) The perf stat of cycles and msr:write_msr for above command before the change: ... Performance counter stats for './perf record --no-timestamp -c 10000 -e cycles:p \ ./perf bench sched pipe -l 1000000' (5 runs): 18,519,557,441 cycles:k 91,195,527 msr:write_msr 29.334476406 seconds time elapsed And after the change: ... Performance counter stats for './perf record --no-timestamp -c 10000 -e cycles:p \ ./perf bench sched pipe -l 1000000' (5 runs): 18,704,973,540 cycles:k 27,184,720 msr:write_msr 16.977875900 seconds time elapsed There's no affect on cycles:k because the sched_task happens with events switched off, however the msr:write_msr tracepoint counter together with almost 50% of time speedup show the improvement. Monitoring LBR event and having extra PEBS drain processing in sched_task callback showed just a little speedup, because the drain function does not do much extra work in case there is no PEBS data. Adding conditions to recognize the configured work that needs to be done in the x86_pmu's sched_task callback. Suggested-by: Peter Zijlstra Signed-off-by: Jiri Olsa Acked-by: Peter Zijlstra (Intel) Cc: Kan Liang Cc: Alexander Shishkin Cc: Jiri Olsa Link: http://lkml.kernel.org/r/20170719075247.GA27506@krava Signed-off-by: Ingo Molnar --- arch/x86/events/intel/core.c | 6 ++---- arch/x86/events/intel/ds.c | 14 ++++++++------ arch/x86/events/intel/lbr.c | 4 ++++ 3 files changed, 14 insertions(+), 10 deletions(-) diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c index ede97710c2f4..98b0f0729527 100644 --- a/arch/x86/events/intel/core.c +++ b/arch/x86/events/intel/core.c @@ -3397,10 +3397,8 @@ static void intel_pmu_cpu_dying(int cpu) static void intel_pmu_sched_task(struct perf_event_context *ctx, bool sched_in) { - if (x86_pmu.pebs_active) - intel_pmu_pebs_sched_task(ctx, sched_in); - if (x86_pmu.lbr_nr) - intel_pmu_lbr_sched_task(ctx, sched_in); + intel_pmu_pebs_sched_task(ctx, sched_in); + intel_pmu_lbr_sched_task(ctx, sched_in); } PMU_FORMAT_ATTR(offcore_rsp, "config1:0-63"); diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c index 6dc8a59e1bfb..a322fed5f8ed 100644 --- a/arch/x86/events/intel/ds.c +++ b/arch/x86/events/intel/ds.c @@ -606,12 +606,6 @@ static inline void intel_pmu_drain_pebs_buffer(void) x86_pmu.drain_pebs(®s); } -void intel_pmu_pebs_sched_task(struct perf_event_context *ctx, bool sched_in) -{ - if (!sched_in) - intel_pmu_drain_pebs_buffer(); -} - /* * PEBS */ @@ -822,6 +816,14 @@ static inline bool pebs_needs_sched_cb(struct cpu_hw_events *cpuc) return cpuc->n_pebs && (cpuc->n_pebs == cpuc->n_large_pebs); } +void intel_pmu_pebs_sched_task(struct perf_event_context *ctx, bool sched_in) +{ + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); + + if (!sched_in && pebs_needs_sched_cb(cpuc)) + intel_pmu_drain_pebs_buffer(); +} + static inline void pebs_update_threshold(struct cpu_hw_events *cpuc) { struct debug_store *ds = cpuc->ds; diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c index eb261656a320..955457a30197 100644 --- a/arch/x86/events/intel/lbr.c +++ b/arch/x86/events/intel/lbr.c @@ -380,8 +380,12 @@ static void __intel_pmu_lbr_save(struct x86_perf_task_context *task_ctx) void intel_pmu_lbr_sched_task(struct perf_event_context *ctx, bool sched_in) { + struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events); struct x86_perf_task_context *task_ctx; + if (!cpuc->lbr_users) + return; + /* * If LBR callstack feature is enabled and the stack was saved when * the task was scheduled out, restore the stack. Otherwise flush -- 2.20.1