From: Peter Zijlstra <peterz@infradead.org>
To: Paul Mackerras <paulus@samba.org>
Cc: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>,
Ingo Molnar <mingo@elte.hu>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] perf_counter: cleanup for __perf_event_sched_in()
Date: Tue, 22 Sep 2009 13:17:10 +0200 [thread overview]
Message-ID: <1253618230.7695.28.camel@twins> (raw)
In-Reply-To: <19128.39768.149110.673711@cargo.ozlabs.ibm.com>
On Tue, 2009-09-22 at 19:39 +1000, Paul Mackerras wrote:
> Xiao Guangrong writes:
>
> > It must be a group leader if event->attr.pinned is "1"
>
> 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). Peter, do you agree or have I missed something?
/me kicks those neurons back to work..
Ah, yes, I think you're right, the second hunk of afedadf2 is a
pessimisation due to the extra branch.
next prev parent reply other threads:[~2009-09-22 11:17 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-22 8:47 [PATCH] perf_counter: cleanup for __perf_event_sched_in() Xiao Guangrong
2009-09-22 9:20 ` Paul Mackerras
2009-09-22 9:27 ` Xiao Guangrong
2009-09-22 9:32 ` [PATCH v2] " Xiao Guangrong
2009-09-22 9:39 ` [PATCH] " Paul Mackerras
2009-09-22 11:17 ` Peter Zijlstra [this message]
2009-09-23 2:45 ` Xiao Guangrong
2009-09-23 3:32 ` Paul Mackerras
2009-09-23 8:10 ` [PATCH 1/2] perf_counter: cleanup for __perf_event_sched_*() Xiao Guangrong
2009-09-23 8:13 ` [PATCH 2/2] perf_counter: optimize for perf_event_init_task() Xiao Guangrong
2009-09-23 8:43 ` Peter Zijlstra
2009-09-25 1:23 ` Xiao Guangrong
2009-09-23 8:40 ` [PATCH 1/2] perf_counter: cleanup for __perf_event_sched_*() Peter Zijlstra
2009-09-25 1:22 ` Xiao Guangrong
2009-09-25 5:51 ` [PATCH 1/2 v2] perf_counter: fix " Xiao Guangrong
2009-09-25 5:54 ` [PATCH 2/2 v2] optimize for perf_event_init_task() Xiao Guangrong
2009-09-25 8:55 ` Peter Zijlstra
2009-10-01 7:31 ` Ingo Molnar
2009-10-01 7:47 ` [tip:perf/urgent] perf_event: Clean up perf_event_init_task() tip-bot for Xiao Guangrong
2009-09-25 8:55 ` [PATCH 1/2 v2] perf_counter: fix for __perf_event_sched_*() Peter Zijlstra
2009-10-01 7:46 ` [tip:perf/urgent] perf_event: Fix event group handling in __perf_event_sched_*() tip-bot for Xiao Guangrong
2009-09-22 11:12 ` [PATCH] perf_counter: cleanup for __perf_event_sched_in() Peter Zijlstra
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