linux-kernel - [PATCH 1/3] perf/core: Update perf_adjust_freq_unthr

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Message-ID: <20231120221932.213710-1-namhyung@kernel.org>
Date:   Mon, 20 Nov 2023 14:19:30 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>
Cc:     Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ian Rogers <irogers@...gle.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Mingwei Zhang <mizhang@...gle.com>
Subject: [PATCH 1/3] perf/core: Update perf_adjust_freq_unthr_context()

It was unnecessarily disabling and enabling PMUs for each event.  It
should be done at PMU level.  Add pmu_ctx->nr_freq counter to check it
at each PMU.  As pmu context has separate active lists for pinned group
and flexible group, factor out a new function to do the job.

Another minor optimization is that it can skip PMUs w/ CAP_NO_INTERRUPT
even if it needs to unthrottle sampling events.

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 include/linux/perf_event.h |  1 +
 kernel/events/core.c       | 68 +++++++++++++++++++++++---------------
 2 files changed, 43 insertions(+), 26 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 0367d748fae0..3eb17dc89f5e 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -879,6 +879,7 @@ struct perf_event_pmu_context {
 
 	unsigned int			nr_events;
 	unsigned int			nr_cgroups;
+	unsigned int			nr_freq;
 
 	atomic_t			refcount; /* event <-> epc */
 	struct rcu_head			rcu_head;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 3eb26c2c6e65..53e2ad73102d 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2275,8 +2275,10 @@ event_sched_out(struct perf_event *event, struct perf_event_context *ctx)
 
 	if (!is_software_event(event))
 		cpc->active_oncpu--;
-	if (event->attr.freq && event->attr.sample_freq)
+	if (event->attr.freq && event->attr.sample_freq) {
 		ctx->nr_freq--;
+		epc->nr_freq--;
+	}
 	if (event->attr.exclusive || !cpc->active_oncpu)
 		cpc->exclusive = 0;
 
@@ -2531,9 +2533,10 @@ event_sched_in(struct perf_event *event, struct perf_event_context *ctx)
 
 	if (!is_software_event(event))
 		cpc->active_oncpu++;
-	if (event->attr.freq && event->attr.sample_freq)
+	if (event->attr.freq && event->attr.sample_freq) {
 		ctx->nr_freq++;
-
+		epc->nr_freq++;
+	}
 	if (event->attr.exclusive)
 		cpc->exclusive = 1;
 
@@ -4096,30 +4099,14 @@ static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count, bo
 	}
 }
 
-/*
- * combine freq adjustment with unthrottling to avoid two passes over the
- * events. At the same time, make sure, having freq events does not change
- * the rate of unthrottling as that would introduce bias.
- */
-static void
-perf_adjust_freq_unthr_context(struct perf_event_context *ctx, bool unthrottle)
+static void perf_adjust_freq_unthr_events(struct list_head *event_list)
 {
 	struct perf_event *event;
 	struct hw_perf_event *hwc;
 	u64 now, period = TICK_NSEC;
 	s64 delta;
 
-	/*
-	 * only need to iterate over all events iff:
-	 * - context have events in frequency mode (needs freq adjust)
-	 * - there are events to unthrottle on this cpu
-	 */
-	if (!(ctx->nr_freq || unthrottle))
-		return;
-
-	raw_spin_lock(&ctx->lock);
-
-	list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
+	list_for_each_entry(event, event_list, active_list) {
 		if (event->state != PERF_EVENT_STATE_ACTIVE)
 			continue;
 
@@ -4127,8 +4114,6 @@ perf_adjust_freq_unthr_context(struct perf_event_context *ctx, bool unthrottle)
 		if (!event_filter_match(event))
 			continue;
 
-		perf_pmu_disable(event->pmu);
-
 		hwc = &event->hw;
 
 		if (hwc->interrupts == MAX_INTERRUPTS) {
@@ -4138,7 +4123,7 @@ perf_adjust_freq_unthr_context(struct perf_event_context *ctx, bool unthrottle)
 		}
 
 		if (!event->attr.freq || !event->attr.sample_freq)
-			goto next;
+			continue;
 
 		/*
 		 * stop the event and update event->count
@@ -4160,8 +4145,39 @@ perf_adjust_freq_unthr_context(struct perf_event_context *ctx, bool unthrottle)
 			perf_adjust_period(event, period, delta, false);
 
 		event->pmu->start(event, delta > 0 ? PERF_EF_RELOAD : 0);
-	next:
-		perf_pmu_enable(event->pmu);
+	}
+}
+
+/*
+ * combine freq adjustment with unthrottling to avoid two passes over the
+ * events. At the same time, make sure, having freq events does not change
+ * the rate of unthrottling as that would introduce bias.
+ */
+static void
+perf_adjust_freq_unthr_context(struct perf_event_context *ctx, bool unthrottle)
+{
+	struct perf_event_pmu_context *pmu_ctx;
+
+	/*
+	 * only need to iterate over all events iff:
+	 * - context have events in frequency mode (needs freq adjust)
+	 * - there are events to unthrottle on this cpu
+	 */
+	if (!(ctx->nr_freq || unthrottle))
+		return;
+
+	raw_spin_lock(&ctx->lock);
+
+	list_for_each_entry(pmu_ctx, &ctx->pmu_ctx_list, pmu_ctx_entry) {
+		if (!(pmu_ctx->nr_freq || unthrottle))
+			continue;
+		if (pmu_ctx->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT)
+			continue;
+
+		perf_pmu_disable(pmu_ctx->pmu);
+		perf_adjust_freq_unthr_events(&pmu_ctx->pinned_active);
+		perf_adjust_freq_unthr_events(&pmu_ctx->flexible_active);
+		perf_pmu_enable(pmu_ctx->pmu);
 	}
 
 	raw_spin_unlock(&ctx->lock);
-- 
2.43.0.rc1.413.gea7ed67945-goog