From: Peter Zijlstra <peterz@infradead.org>
To: David Ahern <dsahern@gmail.com>
Cc: acme@ghostprotocols.net, linux-kernel@vger.kernel.org,
mingo@kernel.org, jolsa@redhat.com,
Frederic Weisbecker <fweisbec@gmail.com>,
Namhyung Kim <namhyung@kernel.org>,
Mike Galbraith <efault@gmx.de>,
Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 4/5] perf record: mmap output file - v5
Date: Tue, 12 Nov 2013 15:57:07 +0100 [thread overview]
Message-ID: <20131112145707.GV5056@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <1384267617-3446-5-git-send-email-dsahern@gmail.com>
On Tue, Nov 12, 2013 at 07:46:56AM -0700, David Ahern wrote:
> When recording raw_syscalls for the entire system, e.g.,
> perf record -e raw_syscalls:*,sched:sched_switch -a -- sleep 1
>
> you end up with a negative feedback loop as perf itself calls write() fairly
> often. This patch handles the problem by mmap'ing the file in chunks of 64M at
> a time and copies events from the event buffers to the file avoiding write
> system calls.
You know this completely fails the moment you trace faults, because
every new access to one of those pages (to mark it dirty) will trigger a
fault. And we'll take a bunch more faults -- one for each page -- than
we ever did write() syscalls.
Anyway the over all performance improvements still make it worth it. But
the above seems like a false argument in favour of this.
next prev parent reply other threads:[~2013-11-12 14:57 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 [this message]
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
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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