The following commit has been merged into the perf/core branch of tip:
Commit-ID: 0259bf63f71e2accfeca4a4e346ede8edcc86aab
Gitweb: https://git.kernel.org/tip/0259bf63f71e2accfeca4a4e346ede8edcc86aab
Author: Namhyung Kim <namhyung@xxxxxxxxxx>
AuthorDate: Tue, 06 Feb 2024 21:05:44 -08:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Wed, 10 Apr 2024 06:13:57 +02:00
perf/core: Optimize 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@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Tested-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>
Reviewed-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240207050545.2727923-1-namhyung@xxxxxxxxxx
---
include/linux/perf_event.h | 6 +++-
kernel/events/core.c | 70 +++++++++++++++++++++++--------------
2 files changed, 50 insertions(+), 26 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index d2a15c0..3e33b36 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -883,6 +883,7 @@ 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;
@@ -897,6 +898,11 @@ struct perf_event_pmu_context {
int rotate_necessary;
};
+static inline bool perf_pmu_ctx_is_active(struct perf_event_pmu_context *epc)
+{
+ return !list_empty(&epc->flexible_active) || !list_empty(&epc->pinned_active);
+}
+
struct perf_event_groups {
struct rb_root tree;
u64 index;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 724e6d7..9566cfb 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2302,8 +2302,10 @@ 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;
@@ -2558,9 +2560,10 @@ 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;
@@ -4123,30 +4126,14 @@ 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;
@@ -4154,8 +4141,6 @@ 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) {
@@ -4165,7 +4150,7 @@ 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
@@ -4187,8 +4172,41 @@ 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 (!perf_pmu_ctx_is_active(pmu_ctx))
+ 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);
|