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authorXiao Guangrong <xiaoguangrong@cn.fujitsu.com>2009-09-25 07:51:17 +0200
committerIngo Molnar <mingo@elte.hu>2009-10-01 09:30:44 +0200
commit8c9ed8e14c342ec5e7f27e7e498f62409a10eb29 (patch)
tree9f4765f480a567a3a6139083bf334ae2f83f9055 /kernel/perf_event.c
parentperf timechart: Add a power-only mode (diff)
downloadlinux-8c9ed8e14c342ec5e7f27e7e498f62409a10eb29.tar.xz
linux-8c9ed8e14c342ec5e7f27e7e498f62409a10eb29.zip
perf_event: Fix event group handling in __perf_event_sched_*()
Paul Mackerras says: "Actually, looking at this more closely, it has to be a group leader anyway since it's at the top level of ctx->group_list. In fact I see four places where we do: list_for_each_entry(event, &ctx->group_list, group_entry) { if (event == event->group_leader) ... or the equivalent, three of which appear to have been introduced by afedadf2 ("perf_counter: Optimize sched in/out of counters") back in May by Peter Z. As far as I can see the if () is superfluous in each case (a singleton event will be a group of 1 and will have its group_leader pointing to itself)." [ See: http://marc.info/?l=linux-kernel&m=125361238901442&w=2 ] And Peter Zijlstra points out this is a bugfix: "The intent was to call event_sched_{in,out}() for single event groups because that's cheaper than group_sched_{in,out}(), however.. - as you noticed, I got the condition wrong, it should have read: list_empty(&event->sibling_list) - it failed to call group_can_go_on() which deals with ->exclusive. - it also doesn't call hw_perf_group_sched_in() which might break power." [ See: http://marc.info/?l=linux-kernel&m=125369523318583&w=2 ] Changelog v1->v2: - Fix the title name according to Peter Zijlstra's suggestion - Remove the comments and WARN_ON_ONCE() as Peter Zijlstra's suggestion Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Paul Mackerras <paulus@samba.org> LKML-Reference: <4ABC5A55.7000208@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to '')
-rw-r--r--kernel/perf_event.c30
1 files changed, 8 insertions, 22 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 0f86feb6db0c..e50543db642a 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -1030,14 +1030,10 @@ void __perf_event_sched_out(struct perf_event_context *ctx,
update_context_time(ctx);
perf_disable();
- if (ctx->nr_active) {
- list_for_each_entry(event, &ctx->group_list, group_entry) {
- if (event != event->group_leader)
- event_sched_out(event, cpuctx, ctx);
- else
- group_sched_out(event, cpuctx, ctx);
- }
- }
+ if (ctx->nr_active)
+ list_for_each_entry(event, &ctx->group_list, group_entry)
+ group_sched_out(event, cpuctx, ctx);
+
perf_enable();
out:
spin_unlock(&ctx->lock);
@@ -1258,12 +1254,8 @@ __perf_event_sched_in(struct perf_event_context *ctx,
if (event->cpu != -1 && event->cpu != cpu)
continue;
- if (event != event->group_leader)
- event_sched_in(event, cpuctx, ctx, cpu);
- else {
- if (group_can_go_on(event, cpuctx, 1))
- group_sched_in(event, cpuctx, ctx, cpu);
- }
+ if (group_can_go_on(event, cpuctx, 1))
+ group_sched_in(event, cpuctx, ctx, cpu);
/*
* If this pinned group hasn't been scheduled,
@@ -1291,15 +1283,9 @@ __perf_event_sched_in(struct perf_event_context *ctx,
if (event->cpu != -1 && event->cpu != cpu)
continue;
- if (event != event->group_leader) {
- if (event_sched_in(event, cpuctx, ctx, cpu))
+ if (group_can_go_on(event, cpuctx, can_add_hw))
+ if (group_sched_in(event, cpuctx, ctx, cpu))
can_add_hw = 0;
- } else {
- if (group_can_go_on(event, cpuctx, can_add_hw)) {
- if (group_sched_in(event, cpuctx, ctx, cpu))
- can_add_hw = 0;
- }
- }
}
perf_enable();
out: