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perf/core: Optimize perf_init_event()

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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: Andi Kleen <andi@firstfloor.org>
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: 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2019-10-17 20:31:03 +02:00 committed by Ingo Molnar
parent db0503e4f6
commit 66d258c5b0
1 changed files with 30 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

41
kernel/events/core.c
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@ -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;
}