Commit 66d258c5 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf/core: Optimize perf_init_event() 



Andi reported that he was hitting the linear search in
perf_init_event() a lot. Make more agressive use of the IDR lookup to
avoid hitting the linear search.

With exception of PERF_TYPE_SOFTWARE (which relies on a hideous hack),
we can put everything in the IDR. On top of that, we can alias
TYPE_HARDWARE and TYPE_HW_CACHE to TYPE_RAW on the lookup side.

This greatly reduces the chances of hitting the linear search.

Reported-by: default avatarAndi Kleen <andi@firstfloor.org>
Signed-off-by: default avatarPeter 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: Kan <kan.liang@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.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>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent db0503e4

kernel/events/core.c

+30 −11
Original line number Diff line number Diff line
@@ -10080,7 +10080,7 @@ static struct lock_class_key cpuctx_lock; 


int perf_pmu_register(struct pmu *pmu, const char *name, int type)

{

	int cpu, ret;

	int cpu, ret, max = PERF_TYPE_MAX;



	mutex_lock(&pmus_lock);

	ret = -ENOMEM;
@@ -10093,12 +10093,17 @@ int perf_pmu_register(struct pmu *pmu, const char *name, int type) 
		goto skip_type;

	pmu->name = name;



	if (type < 0) {

		type = idr_alloc(&pmu_idr, pmu, PERF_TYPE_MAX, 0, GFP_KERNEL);

		if (type < 0) {

			ret = type;

	if (type != PERF_TYPE_SOFTWARE) {

		if (type >= 0)

			max = type;



		ret = idr_alloc(&pmu_idr, pmu, max, 0, GFP_KERNEL);

		if (ret < 0)

			goto free_pdc;

		}



		WARN_ON(type >= 0 && ret != type);



		type = ret;

	}

	pmu->type = type;
@@ -10188,7 +10193,7 @@ free_dev: 
	put_device(pmu->dev);



free_idr:

	if (pmu->type >= PERF_TYPE_MAX)

	if (pmu->type != PERF_TYPE_SOFTWARE)

		idr_remove(&pmu_idr, pmu->type);



free_pdc:
@@ -10210,7 +10215,7 @@ void perf_pmu_unregister(struct pmu *pmu) 
	synchronize_rcu();



	free_percpu(pmu->pmu_disable_count);

	if (pmu->type >= PERF_TYPE_MAX)

	if (pmu->type != PERF_TYPE_SOFTWARE)

		idr_remove(&pmu_idr, pmu->type);

	if (pmu_bus_running) {

		if (pmu->nr_addr_filters)
@@ -10280,9 +10285,8 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event) 


static struct pmu *perf_init_event(struct perf_event *event)

{

	int idx, type, ret;

	struct pmu *pmu;

	int idx;

	int ret;



	idx = srcu_read_lock(&pmus_srcu);
@@ -10295,12 +10299,27 @@ static struct pmu *perf_init_event(struct perf_event *event) 
	}



	rcu_read_lock();

	pmu = idr_find(&pmu_idr, event->attr.type);

	/*

	 * PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE

	 * are often aliases for PERF_TYPE_RAW.

	 */

	type = event->attr.type;

	if (type == PERF_TYPE_HARDWARE || type == PERF_TYPE_HW_CACHE)

		type = PERF_TYPE_RAW;



again:

	pmu = idr_find(&pmu_idr, type);

	rcu_read_unlock();

	if (pmu) {

		ret = perf_try_init_event(pmu, event);

		if (ret == -ENOENT && event->attr.type != type) {

			type = event->attr.type;

			goto again;

		}



		if (ret)

			pmu = ERR_PTR(ret);



		goto unlock;

	}

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