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perf/core: Optimize perf_adjust_freq_unthr_context()

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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@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Mingwei Zhang <mizhang@google.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Reviewed-by: Kan Liang <kan.liang@linux.intel.com>
Link: https://lore.kernel.org/r/20240207050545.2727923-1-namhyung@kernel.org
This commit is contained in:
Namhyung Kim 2024-02-06 21:05:44 -08:00 committed by Ingo Molnar
parent 9794563d4d
commit 0259bf63f7
2 changed files with 50 additions and 26 deletions
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6
include/linux/perf_event.h
View File

@ -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;

70
kernel/events/core.c
View File

@ -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);