linux-kernel - Re: [RFC 2/2] perf/core: Invoke pmu::sched

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Message-ID: <bd97ab7c-039c-b968-3008-8bcd51700c8c@linux.intel.com>
Date:   Thu, 5 Nov 2020 14:39:50 -0500
From:   "Liang, Kan" <kan.liang@...ux.intel.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ingo Molnar <mingo@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>, Gabriel Marin <gmx@...gle.com>
Subject: Re: [RFC 2/2] perf/core: Invoke pmu::sched_task callback for per-cpu
 events



On 11/5/2020 10:54 AM, Namhyung Kim wrote:
>> -void perf_sched_cb_inc(struct pmu *pmu)
>> +void perf_sched_cb_inc(struct pmu *pmu, bool systemwide)
>>    {
>>          struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
>>
>> -       if (!cpuctx->sched_cb_usage++)
>> -               list_add(&cpuctx->sched_cb_entry, this_cpu_ptr(&sched_cb_list));
>> +       cpuctx->sched_cb_usage++;
>>
>> -       this_cpu_inc(perf_sched_cb_usages);
>> +       if (systemwide) {
>> +               this_cpu_inc(perf_sched_cb_usages);
>> +               list_add(&cpuctx->sched_cb_entry, this_cpu_ptr(&sched_cb_list));
> You need to check the value and make sure it's added only once.

Right, maybe we have to add a new variable for that.


diff --git a/arch/powerpc/perf/core-book3s.c 
b/arch/powerpc/perf/core-book3s.c
index 6586f7e71cfb..63c9b87cab5e 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -380,7 +380,7 @@ static void power_pmu_bhrb_enable(struct perf_event 
*event)
  		cpuhw->bhrb_context = event->ctx;
  	}
  	cpuhw->bhrb_users++;
-	perf_sched_cb_inc(event->ctx->pmu);
+	perf_sched_cb_inc(event->ctx->pmu, !(event->attach_state & 
PERF_ATTACH_TASK));
  }

  static void power_pmu_bhrb_disable(struct perf_event *event)
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 444e5f061d04..a34b90c7fa6d 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1022,9 +1022,9 @@ pebs_update_state(bool needed_cb, struct 
cpu_hw_events *cpuc,

  	if (needed_cb != pebs_needs_sched_cb(cpuc)) {
  		if (!needed_cb)
-			perf_sched_cb_inc(pmu);
+			perf_sched_cb_inc(pmu, !(event->attach_state & PERF_ATTACH_TASK));
  		else
-			perf_sched_cb_dec(pmu);
+			perf_sched_cb_dec(pmu, !(event->attach_state & PERF_ATTACH_TASK));

  		update = true;
  	}
diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 8961653c5dd2..8d4d02cde3d4 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -693,7 +693,7 @@ void intel_pmu_lbr_add(struct perf_event *event)
  	 */
  	if (x86_pmu.intel_cap.pebs_baseline && event->attr.precise_ip > 0)
  		cpuc->lbr_pebs_users++;
-	perf_sched_cb_inc(event->ctx->pmu);
+	perf_sched_cb_inc(event->ctx->pmu, !(event->attach_state & 
PERF_ATTACH_TASK));
  	if (!cpuc->lbr_users++ && !event->total_time_running)
  		intel_pmu_lbr_reset();

@@ -740,7 +740,7 @@ void intel_pmu_lbr_del(struct perf_event *event)
  	cpuc->lbr_users--;
  	WARN_ON_ONCE(cpuc->lbr_users < 0);
  	WARN_ON_ONCE(cpuc->lbr_pebs_users < 0);
-	perf_sched_cb_dec(event->ctx->pmu);
+	perf_sched_cb_dec(event->ctx->pmu, !(event->attach_state & 
PERF_ATTACH_TASK));
  }

  static inline bool vlbr_exclude_host(void)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index a1b91f2de264..14f936385cc8 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -875,6 +875,7 @@ struct perf_cpu_context {

  	struct list_head		sched_cb_entry;
  	int				sched_cb_usage;
+	int				sched_cb_sw_usage;

  	int				online;
  	/*
@@ -967,8 +968,8 @@ extern const struct perf_event_attr 
*perf_event_attrs(struct perf_event *event);
  extern void perf_event_print_debug(void);
  extern void perf_pmu_disable(struct pmu *pmu);
  extern void perf_pmu_enable(struct pmu *pmu);
-extern void perf_sched_cb_dec(struct pmu *pmu);
-extern void perf_sched_cb_inc(struct pmu *pmu);
+extern void perf_sched_cb_dec(struct pmu *pmu, bool systemwide);
+extern void perf_sched_cb_inc(struct pmu *pmu, bool systemwide);
  extern int perf_event_task_disable(void);
  extern int perf_event_task_enable(void);

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 66a9bd71f3da..af75859c9138 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3484,22 +3484,32 @@ static void perf_event_context_sched_out(struct 
task_struct *task, int ctxn,

  static DEFINE_PER_CPU(struct list_head, sched_cb_list);

-void perf_sched_cb_dec(struct pmu *pmu)
+void perf_sched_cb_dec(struct pmu *pmu, bool systemwide)
  {
  	struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);

+	--cpuctx->sched_cb_usage;
+
+	if (!systemwide)
+		return;
+
  	this_cpu_dec(perf_sched_cb_usages);

-	if (!--cpuctx->sched_cb_usage)
+	if (!--cpuctx->sched_cb_sw_usage)
  		list_del(&cpuctx->sched_cb_entry);
  }


-void perf_sched_cb_inc(struct pmu *pmu)
+void perf_sched_cb_inc(struct pmu *pmu, bool systemwide)
  {
  	struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);

-	if (!cpuctx->sched_cb_usage++)
+	cpuctx->sched_cb_usage++;
+
+	if (!systemwide)
+		return;
+
+	if (!cpuctx->sched_cb_sw_usage++)
  		list_add(&cpuctx->sched_cb_entry, this_cpu_ptr(&sched_cb_list));

  	this_cpu_inc(perf_sched_cb_usages);



Thanks,
Kan