perf/core: Optimize perf_init_event() for TYPE_SOFTWARE

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).

Signed-off-by: Liang, Kan <kan.liang@linux.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: 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>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4d67c5d35c137ff08e771a44f802baea258a7d7b..cfd89b4a02d80d9de1f6996a00d198c14051bcd8 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10180,7 +10180,16 @@ got_cpu_context:
        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: