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author | Xiao Guangrong <xiaoguangrong@cn.fujitsu.com> | 2009-09-25 13:51:17 +0800 |
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committer | Ingo Molnar <mingo@elte.hu> | 2009-10-01 09:30:44 +0200 |
commit | 8c9ed8e14c342ec5e7f27e7e498f62409a10eb29 (patch) | |
tree | 9f4765f480a567a3a6139083bf334ae2f83f9055 /kernel/perf_event.c | |
parent | 39a90a8ef17fe6fbf4b45e46e3c10d3b8b4a3dea (diff) | |
download | linux-8c9ed8e14c342ec5e7f27e7e498f62409a10eb29.tar.bz2 |
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 'kernel/perf_event.c')
-rw-r--r-- | kernel/perf_event.c | 30 |
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: |