linux-kernel - Re: [RFC][PATCH 1/7] perf/x86/intel: Rework the large PEBS setup code

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Message-ID: <20160708222509.GL30927@twins.programming.kicks-ass.net>
Date:	Sat, 9 Jul 2016 00:25:09 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	mingo@...nel.org, acme@...nel.org, linux-kernel@...r.kernel.org,
	andi@...stfloor.org, eranian@...gle.com, jolsa@...nel.org,
	torvalds@...ux-foundation.org, davidcc@...gle.com,
	alexander.shishkin@...ux.intel.com, namhyung@...nel.org,
	kan.liang@...el.com, khandual@...ux.vnet.ibm.com
Subject: Re: [RFC][PATCH 1/7] perf/x86/intel: Rework the large PEBS setup code

On Sat, Jul 09, 2016 at 12:00:47AM +0200, Peter Zijlstra wrote:
> Yes, you're right. Let me try and see if I can make that better.

Something like so?

---
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -831,6 +831,18 @@ static inline void pebs_update_threshold
 	ds->pebs_interrupt_threshold = threshold;
 }
 
+static void pebs_update_state(bool needs_cb, struct cpu_hw_events *cpuc, struct pmu *pmu)
+{
+	if (needs_cb != pebs_needs_sched_cb(cpuc)) {
+		if (!needs_cb)
+			perf_sched_cb_inc(pmu);
+		else
+			perf_sched_cb_dec(pmu);
+
+		pebs_update_threshold(cpuc);
+	}
+}
+
 static void intel_pmu_pebs_add(struct perf_event *event)
 {
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
@@ -841,10 +853,7 @@ static void intel_pmu_pebs_add(struct pe
 	if (hwc->flags & PERF_X86_EVENT_FREERUNNING)
 		cpuc->n_large_pebs++;
 
-	if (!needs_cb && pebs_needs_sched_cb(cpuc))
-		perf_sched_cb_inc(event->ctx->pmu);
-
-	pebs_update_threshold(cpuc);
+	pebs_update_state(needs_cb, cpuc, event->ctx->pmu);
 }
 
 void intel_pmu_pebs_enable(struct perf_event *event)
@@ -884,11 +893,7 @@ static void intel_pmu_pebs_del(struct pe
 	if (hwc->flags & PERF_X86_EVENT_FREERUNNING)
 		cpuc->n_large_pebs--;
 
-	if (needs_cb && !pebs_needs_sched_cb(cpuc))
-		perf_sched_cb_dec(event->ctx->pmu);
-
-	if (cpuc->n_pebs)
-		pebs_update_threshold(cpuc);
+	pebs_update_state(needs_cb, cpuc, event->ctx->pmu);
 }
 
 void intel_pmu_pebs_disable(struct perf_event *event)