From: "Liang, Kan" <kan.li...@linux.intel.com>
Andi reported that he was hitting the linear search in
perf_init_event() a lot. Now that all !TYPE_SOFTWARE events should hit
the IDR, make sure the TYPE_SOFTWARE events are at the head of the
list such that we'll quickly find the right PMU (provided a valid
event was given).
Reported-by: Andi Kleen <a...@firstfloor.org>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
---
kernel/events/core.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10167,7 +10167,16 @@ int perf_pmu_register(struct pmu *pmu, c
if (!pmu->event_idx)
pmu->event_idx = perf_event_idx_default;
- list_add_rcu(&pmu->entry, &pmus);
+ /*
+ * Ensure the TYPE_SOFTWARE PMUs are at the head of the list,
+ * since these cannot be in the IDR. This way the linear search
+ * is fast, provided a valid software event is provided.
+ */
+ if (type == PERF_TYPE_SOFTWARE || !name)
+ list_add_rcu(&pmu->entry, &pmus);
+ else
+ list_add_tail_rcu(&pmu->entry, &pmus);
+
atomic_set(&pmu->exclusive_cnt, 0);
ret = 0;
unlock:
