perf/core: Optimize side-band event delivery

The perf_event_aux() function iterates all PMUs and all events in
their respective per-CPU contexts to find the events to deliver
side-band records to.

For example, the brk test case in lkp triggers many mmap() operations,
which, if we're also running perf, results in many perf_event_aux()
invocations.

If we enable uncore PMU support (even when uncore events are not used),
dozens of uncore PMUs will be iterated, which can significantly
decrease brk_test's throughput.

For example, the brk throughput:

  without uncore PMUs: 2647573 ops_per_sec
  with    uncore PMUs: 1768444 ops_per_sec

... a 33% reduction.

To get at the per-CPU events that need side-band records, this patch
puts these events on a per-CPU list, this avoids iterating the PMUs
and any events that do not need side-band records.

Per task events are unchanged to avoid extra overhead on the context
switch paths.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reported-by: Huang, Ying <ying.huang@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1458757477-3781-1-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Kan Liang 2016-03-23 11:24:37 -07:00 committed by Ingo Molnar
parent 42c4fb7747
commit f2fb6bef92
2 changed files with 79 additions and 12 deletions

View File

@ -517,6 +517,11 @@ struct swevent_hlist {
struct perf_cgroup;
struct ring_buffer;
struct pmu_event_list {
raw_spinlock_t lock;
struct list_head list;
};
/**
* struct perf_event - performance event kernel representation:
*/
@ -675,6 +680,7 @@ struct perf_event {
int cgrp_defer_enabled;
#endif
struct list_head sb_list;
#endif /* CONFIG_PERF_EVENTS */
};

View File

@ -335,6 +335,7 @@ static atomic_t perf_sched_count;
static DEFINE_PER_CPU(atomic_t, perf_cgroup_events);
static DEFINE_PER_CPU(int, perf_sched_cb_usages);
static DEFINE_PER_CPU(struct pmu_event_list, pmu_sb_events);
static atomic_t nr_mmap_events __read_mostly;
static atomic_t nr_comm_events __read_mostly;
@ -3665,6 +3666,26 @@ static void free_event_rcu(struct rcu_head *head)
static void ring_buffer_attach(struct perf_event *event,
struct ring_buffer *rb);
static void detach_sb_event(struct perf_event *event)
{
struct pmu_event_list *pel = per_cpu_ptr(&pmu_sb_events, event->cpu);
raw_spin_lock(&pel->lock);
list_del_rcu(&event->sb_list);
raw_spin_unlock(&pel->lock);
}
static void unaccount_pmu_sb_event(struct perf_event *event)
{
if (event->parent)
return;
if (event->attach_state & PERF_ATTACH_TASK)
return;
detach_sb_event(event);
}
static void unaccount_event_cpu(struct perf_event *event, int cpu)
{
if (event->parent)
@ -3728,6 +3749,8 @@ static void unaccount_event(struct perf_event *event)
}
unaccount_event_cpu(event, event->cpu);
unaccount_pmu_sb_event(event);
}
static void perf_sched_delayed(struct work_struct *work)
@ -5888,13 +5911,25 @@ perf_event_aux_task_ctx(perf_event_aux_output_cb output, void *data,
rcu_read_unlock();
}
static void perf_event_sb_iterate(perf_event_aux_output_cb output, void *data)
{
struct pmu_event_list *pel = this_cpu_ptr(&pmu_sb_events);
struct perf_event *event;
list_for_each_entry_rcu(event, &pel->list, sb_list) {
if (event->state < PERF_EVENT_STATE_INACTIVE)
continue;
if (!event_filter_match(event))
continue;
output(event, data);
}
}
static void
perf_event_aux(perf_event_aux_output_cb output, void *data,
struct perf_event_context *task_ctx)
{
struct perf_cpu_context *cpuctx;
struct perf_event_context *ctx;
struct pmu *pmu;
int ctxn;
/*
@ -5909,20 +5944,15 @@ perf_event_aux(perf_event_aux_output_cb output, void *data,
}
rcu_read_lock();
list_for_each_entry_rcu(pmu, &pmus, entry) {
cpuctx = get_cpu_ptr(pmu->pmu_cpu_context);
if (cpuctx->unique_pmu != pmu)
goto next;
perf_event_aux_ctx(&cpuctx->ctx, output, data, false);
ctxn = pmu->task_ctx_nr;
if (ctxn < 0)
goto next;
preempt_disable();
perf_event_sb_iterate(output, data);
for_each_task_context_nr(ctxn) {
ctx = rcu_dereference(current->perf_event_ctxp[ctxn]);
if (ctx)
perf_event_aux_ctx(ctx, output, data, false);
next:
put_cpu_ptr(pmu->pmu_cpu_context);
}
preempt_enable();
rcu_read_unlock();
}
@ -8615,6 +8645,32 @@ unlock:
return pmu;
}
static void attach_sb_event(struct perf_event *event)
{
struct pmu_event_list *pel = per_cpu_ptr(&pmu_sb_events, event->cpu);
raw_spin_lock(&pel->lock);
list_add_rcu(&event->sb_list, &pel->list);
raw_spin_unlock(&pel->lock);
}
static void account_pmu_sb_event(struct perf_event *event)
{
struct perf_event_attr *attr = &event->attr;
if (event->parent)
return;
if (event->attach_state & PERF_ATTACH_TASK)
return;
if (attr->mmap || attr->mmap_data || attr->mmap2 ||
attr->comm || attr->comm_exec ||
attr->task ||
attr->context_switch)
attach_sb_event(event);
}
static void account_event_cpu(struct perf_event *event, int cpu)
{
if (event->parent)
@ -8695,6 +8751,8 @@ static void account_event(struct perf_event *event)
enabled:
account_event_cpu(event, event->cpu);
account_pmu_sb_event(event);
}
/*
@ -10203,6 +10261,9 @@ static void __init perf_event_init_all_cpus(void)
swhash = &per_cpu(swevent_htable, cpu);
mutex_init(&swhash->hlist_mutex);
INIT_LIST_HEAD(&per_cpu(active_ctx_list, cpu));
INIT_LIST_HEAD(&per_cpu(pmu_sb_events.list, cpu));
raw_spin_lock_init(&per_cpu(pmu_sb_events.lock, cpu));
}
}