From: Peter Zijlstra <peterz@infradead.org>
To: Jiri Olsa <jolsa@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>,
linux-kernel@vger.kernel.org, Andi Kleen <andi@firstfloor.org>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Corey Ashford <cjashfor@linux.vnet.ibm.com>,
David Ahern <dsahern@gmail.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@kernel.org>,
"Jen-Cheng(Tommy) Huang" <tommy24@gatech.edu>,
Namhyung Kim <namhyung@kernel.org>,
Paul Mackerras <paulus@samba.org>,
Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 1/9] perf: Remove redundant parent context check from context_equiv
Date: Mon, 8 Sep 2014 11:48:55 +0200 [thread overview]
Message-ID: <20140908094855.GR3588@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20140908094548.GA6758@twins.programming.kicks-ass.net>
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On Mon, Sep 08, 2014 at 11:45:48AM +0200, Peter Zijlstra wrote:
> On Mon, Sep 08, 2014 at 11:43:48AM +0200, Jiri Olsa wrote:
> > On Tue, Sep 02, 2014 at 12:50:36PM +0200, Peter Zijlstra wrote:
> > > On Mon, Aug 25, 2014 at 04:45:35PM +0200, Jiri Olsa wrote:
> > > > As described in commit:
> > > > 1f9a7268c67f perf: Do not allow optimized switch for non-cloned events
> > > > we dont allow optimized switch for non cloned contexts.
> > > >
> > > > There's no need now to check if one of the context is parent
> > > > of the other in context_equiv function.
> > > >
> > >
> > > OK, so talk to me about that patch; it looks like you're slowly
> > > reverting: 5a3126d4fe7c ("perf: Fix the perf context switch
> > > optimization").
> > >
> > > So what exactly is the problem? I'm still jet-lagged and not seeing it.
> >
> > the problem is, that we cannot allow non-cloned context
> > to be part of the optimized switch for reasons explained
> > in commit 1f9a7268c67f
>
> The thing is; I don't understand those reasons. That commit log doesn't
> explain.
Ah wait, I finally see. I think we want to fix that exit path, not
disallow the cloning.
The thing is, by not allowing this optimization simple things like eg.
pipe-test say very expensive.
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next prev parent reply other threads:[~2014-09-08 9:49 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-25 14:45 [RFCv2 0/9] perf: Allow leader sampling on inherited events Jiri Olsa
2014-08-25 14:45 ` [PATCH 1/9] perf: Remove redundant parent context check from context_equiv Jiri Olsa
2014-09-02 10:50 ` Peter Zijlstra
2014-09-08 9:43 ` Jiri Olsa
2014-09-08 9:45 ` Peter Zijlstra
2014-09-08 9:48 ` Peter Zijlstra [this message]
2014-09-08 10:01 ` Peter Zijlstra
2014-09-08 11:39 ` Peter Zijlstra
2014-09-08 12:19 ` Jiri Olsa
2014-09-08 13:20 ` Peter Zijlstra
2014-09-08 12:32 ` Jiri Olsa
2014-09-08 12:01 ` Jiri Olsa
2014-09-08 13:34 ` Peter Zijlstra
2014-09-08 15:13 ` Peter Zijlstra
2014-09-08 16:45 ` Jiri Olsa
2014-09-09 10:20 ` Peter Zijlstra
2014-09-10 13:57 ` Peter Zijlstra
2014-09-10 14:35 ` Jiri Olsa
2014-09-24 14:58 ` [tip:perf/core] Revert "perf: Do not allow optimized switch for non-cloned events" tip-bot for Jiri Olsa
2014-08-25 14:45 ` [PATCH 2/9] perf: Deny optimized switch for events read by PERF_SAMPLE_READ Jiri Olsa
2014-09-02 10:52 ` Peter Zijlstra
2014-09-08 10:00 ` Jiri Olsa
2014-09-08 10:11 ` Peter Zijlstra
2014-09-08 16:39 ` Jiri Olsa
2014-08-25 14:45 ` [PATCH 3/9] perf: Allow PERF_FORMAT_GROUP format on inherited events Jiri Olsa
2014-08-25 14:45 ` [PATCH 4/9] perf tools: Add support to traverse xyarrays Jiri Olsa
2014-08-25 14:45 ` [PATCH 5/9] perf tools: Add pr_warning_once debug macro Jiri Olsa
2014-08-25 14:45 ` [PATCH 6/9] perf tools: Add hash of periods for struct perf_sample_id Jiri Olsa
2014-08-25 14:45 ` [PATCH 7/9] perf tools: Allow PERF_FORMAT_GROUP for inherited events Jiri Olsa
2014-08-25 14:45 ` [PATCH 8/9] perf script: Add period data column Jiri Olsa
2014-08-27 14:33 ` David Ahern
2014-10-17 16:10 ` Jiri Olsa
2014-10-17 18:22 ` Arnaldo Carvalho de Melo
2014-10-18 7:07 ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2014-08-25 14:45 ` [PATCH 9/9] perf script: Add period as a default output column Jiri Olsa
2014-08-27 14:40 ` David Ahern
2014-10-17 16:11 ` Jiri Olsa
2014-10-18 7:07 ` [tip:perf/urgent] " tip-bot for Jiri Olsa
2014-08-25 14:51 ` [RFCv2 0/9] perf: Allow leader sampling on inherited events Jiri Olsa
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