From: Arun Sharma <aruns@google.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, paulus@samba.org,
davem@davemloft.net, fweisbec@gmail.com
Subject: Re: [PATCH] perf: implement recording/reporting per-cpu samples
Date: Mon, 3 May 2010 13:53:19 -0700 [thread overview]
Message-ID: <w2u850c51c31005031353x9be8ca7h90c244d64675ce3e@mail.gmail.com> (raw)
In-Reply-To: <1272919356.1642.154.camel@laptop>
On Mon, May 3, 2010 at 1:42 PM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Mon, 2010-05-03 at 13:38 -0700, Arun Sharma wrote:
> > Enable PERF_SAMPLE_CPU by default. Implement --sort cpu.
>
> Why? The downside is that you unconditionally grow each sample and thus
> increase the overhead for something that doesn't make sense for the
> normal (task-inherit) case.
In a shared multi-core environment, users want to analyze why their
program was slow. In particular, if the code ran slower only on
certain CPUs due to interference from other programs or kernel
threads, they want to know that.
But that's just our use case. The patch is mostly about --sort cpu
option. If you want to drop the part that enables PERF_SAMPLE_CPU by
default, that's fine by me.
-Arun
next prev parent reply other threads:[~2010-05-03 20:53 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-03 20:38 [PATCH] perf: implement recording/reporting per-cpu samples Arun Sharma
2010-05-03 20:42 ` Peter Zijlstra
2010-05-03 20:53 ` Arun Sharma [this message]
2010-05-04 9:16 ` Peter Zijlstra
2010-05-05 18:16 ` Arun Sharma
2010-05-27 18:08 ` Peter Zijlstra
2010-05-27 18:28 ` Arnaldo Carvalho de Melo
2010-05-27 18:41 ` Arnaldo Carvalho de Melo
2010-05-27 20:54 ` Arun Sharma
2010-05-27 21:53 ` Arnaldo Carvalho de Melo
2010-05-27 23:16 ` Arnaldo Carvalho de Melo
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