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From: Peter Zijlstra on 21 May 2010 10:30
Only child counters adding back their values into the parent counter
are responsible for cross-cpu updates to event->count.

So if we pull that out into a new child_count variable, we get an
event->count that is only modified locally.

Signed-off-by: Peter Zijlstra <a.p.zijlstra(a)chello.nl>
LKML-Reference: <new-submission>
---
include/linux/perf_event.h | 1 +
kernel/perf_event.c | 4 ++--
2 files changed, 3 insertions(+), 2 deletions(-)

Index: linux-2.6/include/linux/perf_event.h
===================================================================
--- linux-2.6.orig/include/linux/perf_event.h
+++ linux-2.6/include/linux/perf_event.h
@@ -648,6 +648,7 @@ struct perf_event {

enum perf_event_active_state state;
atomic64_t count;
+ atomic64_t child_count;

/*
* These are the total time in nanoseconds that the event
Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -1703,7 +1703,7 @@ static void __perf_event_read(void *info

static inline u64 perf_event_count(struct perf_event *event)
{
- return atomic64_read(&event->count);
+ return atomic64_read(&event->count) + atomic64_read(&event->child_count);
}

static u64 perf_event_read(struct perf_event *event)
@@ -5282,7 +5282,7 @@ static void sync_child_event(struct perf
/*
* Add back the child's count to the parent's count:
*/
- atomic64_add(child_val, &parent_event->count);
+ atomic64_add(child_val, &parent_event->child_count);
atomic64_add(child_event->total_time_enabled,
&parent_event->child_total_time_enabled);
atomic64_add(child_event->total_time_running,


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Next: [PATCH 2/4] perf: Add perf_event_count()