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From: Namhyung Kim <namhyung@kernel.org>
To: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
	linux-kernel@vger.kernel.org, jolsa@redhat.com,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Mike Galbraith <efault@gmx.de>,
	Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 4/5] perf record: mmap output file - v5
Date: Tue, 19 Nov 2013 11:30:45 +0900	[thread overview]
Message-ID: <87ob5ht962.fsf@sejong.aot.lge.com> (raw)
In-Reply-To: <528ACA41.4030202@gmail.com> (David Ahern's message of "Mon, 18 Nov 2013 19:17:37 -0700")

On Mon, 18 Nov 2013 19:17:37 -0700, David Ahern wrote:
> On 11/18/13, 7:13 PM, Namhyung Kim wrote:
>> I think it should be
>>
>>    perf record -e cycles -F 4000 -e faults -c 1 --call-graph dwarf,8192 -a -- sleep 1
>>
>> (at least to generate the feedback spiral more efficiently..)
>
> you don't need the cycles. faults by itself works. Each event contains
> 2 pages of data in the sample. With mmap-based output a single
> sample (1 page fault in any process) generates 2-3 page faults by perf
> which cause 2-3 >8k samples to be generated, which generates faults,
> ....

But after perf touches all pages in ring-buffer and stack, it won't
generate page-faults for itself anymore, right?

Hmm.. thinking it again, perf has all ring-buffer pages in memory when
mmap() called, right?  If so why not doing something like MAP_POPULATE
so that it doesn't need to generate minor-faults?

Thanks,
Namhyung

  reply	other threads:[~2013-11-19  2:30 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-11-12 14:46 [PATCH 0/5] " David Ahern
2013-11-12 14:46 ` [PATCH 1/5] perf record: Fix segfault with --no-mmap-pages David Ahern
2013-11-12 21:57   ` [tip:perf/urgent] " tip-bot for David Ahern
2013-11-12 14:46 ` [PATCH 2/5] perf tool: Round mmap pages to power 2 - v2 David Ahern
2013-11-12 21:57   ` [tip:perf/urgent] perf evlist: " tip-bot for David Ahern
2013-11-12 14:46 ` [PATCH 3/5] perf tool: Refactor mmap_pages parsing David Ahern
2013-11-12 21:57   ` [tip:perf/urgent] perf evlist: " tip-bot for David Ahern
2013-11-12 14:46 ` [PATCH 4/5] perf record: mmap output file - v5 David Ahern
2013-11-12 14:57   ` Peter Zijlstra
2013-11-12 15:07     ` Arnaldo Carvalho de Melo
2013-11-12 15:19       ` Peter Zijlstra
2013-11-12 15:36         ` David Ahern
2013-11-12 21:11           ` Ingo Molnar
2013-11-13 11:34             ` Peter Zijlstra
2013-11-13 11:50               ` Ingo Molnar
2013-11-13 12:16                 ` Peter Zijlstra
2013-11-13 14:29                 ` David Ahern
2013-11-15 16:41               ` David Ahern
2013-11-18  9:01                 ` Peter Zijlstra
2013-11-18  9:40                   ` Ingo Molnar
2013-11-19  0:24                     ` Namhyung Kim
2013-11-19  0:34                       ` David Ahern
2013-11-19  1:48                         ` Namhyung Kim
2013-11-19  2:02                         ` Namhyung Kim
2013-11-19  2:13                         ` Namhyung Kim
2013-11-19  2:17                           ` David Ahern
2013-11-19  2:30                             ` Namhyung Kim [this message]
2013-11-19  2:33                               ` David Ahern
2013-11-19  2:36                                 ` Namhyung Kim
2013-11-19  6:58                                 ` Ingo Molnar
2013-11-19 11:48                                   ` Peter Zijlstra
2013-11-19 11:49                                     ` Peter Zijlstra
2013-11-19 13:13                                       ` Ingo Molnar
2013-11-19 13:45                                         ` Peter Zijlstra
2013-11-19 15:31                                           ` Ingo Molnar
2013-11-19 16:09                                             ` David Ahern
2013-11-19 16:14                                               ` Ingo Molnar
2013-11-19 12:08                         ` Peter Zijlstra
2013-11-19  6:54                       ` Ingo Molnar
2013-11-12 14:46 ` [PATCH 5/5] perf record: Handle out of space failures writing data with mmap David Ahern
2013-11-12 21:19   ` Ingo Molnar
2013-11-13 14:33     ` David Ahern

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