perf/core: Split perf_event_read() and perf_event_count()

perf_event_read() does two things:

	- call the PMU to read/update the counter value, and
	- compute the total count of the event and its children

Not all callers need both. perf_event_reset() for instance needs the
first piece but doesn't need the second.  Similarly, when we implement
the ability to read a group of events using the transaction interface,
we would need the two pieces done independently.

Break up perf_event_read() and have it just read/update the counter
and have the callers compute the total count if necessary.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
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/1441336073-22750-4-git-send-email-sukadev@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index c80cee82959fe2043388010644068ccdc1b8cc97..260bf8cfed51221f901787866a07e909c27828ac 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3275,7 +3275,7 @@ u64 perf_event_read_local(struct perf_event *event)
        return val;
 }
 
-static u64 perf_event_read(struct perf_event *event)
+static void perf_event_read(struct perf_event *event)
 {
        /*
         * If event is enabled and currently active on a CPU, update the
@@ -3301,8 +3301,6 @@ static u64 perf_event_read(struct perf_event *event)
                update_event_times(event);
                raw_spin_unlock_irqrestore(&ctx->lock, flags);
        }
-
-       return perf_event_count(event);
 }
 
 /*
@@ -3818,14 +3816,18 @@ u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
        *running = 0;
 
        mutex_lock(&event->child_mutex);
-       total += perf_event_read(event);
+
+       perf_event_read(event);
+       total += perf_event_count(event);
+
        *enabled += event->total_time_enabled +
                        atomic64_read(&event->child_total_time_enabled);
        *running += event->total_time_running +
                        atomic64_read(&event->child_total_time_running);
 
        list_for_each_entry(child, &event->child_list, child_list) {
-               total += perf_event_read(child);
+               perf_event_read(child);
+               total += perf_event_count(child);
                *enabled += child->total_time_enabled;
                *running += child->total_time_running;
        }
@@ -3985,7 +3987,7 @@ static unsigned int perf_poll(struct file *file, poll_table *wait)
 
 static void _perf_event_reset(struct perf_event *event)
 {
-       (void)perf_event_read(event);
+       perf_event_read(event);
        local64_set(&event->count, 0);
        perf_event_update_userpage(event);
 }