From: David Ahern <dsahern@gmail.com>
To: Namhyung Kim <namhyung@kernel.org>
Cc: acme@ghostprotocols.net, linux-kernel@vger.kernel.org,
Ingo Molnar <mingo@kernel.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Jiri Olsa <jolsa@redhat.com>, Mike Galbraith <efault@gmx.de>,
Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH] perf record: mmap output file - v2
Date: Tue, 15 Oct 2013 19:58:34 -0600 [thread overview]
Message-ID: <525DF2CA.1060102@gmail.com> (raw)
In-Reply-To: <87haci9e31.fsf@sejong.aot.lge.com>
On 10/15/13 7:52 PM, Namhyung Kim wrote:
> Aha, okay. So it mostly matters to syscall tracing, right? For a
> normal record session, it seems that the effect is not that large:
Yes, that's in the description "When recording raw_syscalls for the
entire system"
There is a small benefit to all record sessions -- mmap+memcpy has less
overhead than write(). I still need to look at Ingo's suggestion to use
non-temporal stores which might reduce the overhead of the memcpy.
Try a workload that generates a HUGE data file -- say a full kernel
build (e.g., perf record -g -- make O=/tmp/kbuild -j 16). You should see
a much larger benefit from the mmap route. Be sure to use your callchain
enhancements to look at that 1+G file. ;-)
David
prev parent reply other threads:[~2013-10-16 1:58 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-15 2:55 [PATCH] perf record: mmap output file - v2 David Ahern
2013-10-15 6:02 ` Ingo Molnar
2013-10-15 7:09 ` Namhyung Kim
2013-10-15 7:25 ` Ingo Molnar
2013-10-15 8:17 ` Namhyung Kim
2013-10-15 12:22 ` Jiri Olsa
2013-10-15 13:20 ` Ingo Molnar
2013-10-15 13:25 ` David Ahern
2013-10-16 1:24 ` Namhyung Kim
2013-10-15 7:31 ` Namhyung Kim
2013-10-15 7:44 ` Ingo Molnar
2013-10-15 13:45 ` David Ahern
2013-10-15 13:35 ` David Ahern
2013-10-16 1:52 ` Namhyung Kim
2013-10-16 1:58 ` David Ahern [this message]
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