linux-kernel - Re: [PATCH 2.6.28 1/2] memory: improve find

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Message-ID: <8c5a844a0902010319t20b853d0t6c156ecc84543f30@mail.gmail.com>
Date:	Sun, 1 Feb 2009 13:19:10 +0200
From:	Daniel Lowengrub <lowdanie@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.28 1/2] memory: improve find_vma

On 1/29/09, Ingo Molnar <mingo@...e.hu> wrote:
> Here's an mmap performance tester:
>
>    http://redhat.com/~mingo/misc/mmap-perf.c
>
> maybe that shows a systematic effect. If you've got a Core2 based
> test-system then you could try perfstat as well, for much more precise
> instruction counts. (can give you more info about how to do that if you
> have such a test-system.)
>
>        Ingo
>
I compiled mmap-perf.c an ran it with ./mmap-perf 1 (not as root, does
that matter?).  As obvious from the code, the output that I got was
the final state of the /proc/[self]/maps file.  How does this
information tell me about performance?  Anyhow, here're the first 10
lines of the [heap] part of the output using the standard kernel:
0965b000-0967c000 rw-p 0965b000 00:00 0          [heap]
86007000-86009000 rw-p 86007000 00:00 0
86009000-8600a000 ---p 86009000 00:00 0
86018000-8601b000 rw-p 86018000 00:00 0
8601c000-86023000 -w-p 8601c000 00:00 0
86023000-86026000 rw-p 86023000 00:00 0
86026000-86029000 r--p 86026000 00:00 0
8603e000-86040000 rw-p 8603e000 00:00 0
86048000-8604c000 r--p 86048000 00:00 0
8604f000-86054000 ---p 8604f000 00:00 0
and here're the first 10 lines of the output with the patch applied:
09596000-095b7000 rw-p 09596000 00:00 0          [heap]
860ab000-860ad000 rw-p 860ab000 00:00 0
860ad000-860ae000 ---p 860ad000 00:00 0
860bc000-860bf000 rw-p 860bc000 00:00 0
860c0000-860c7000 -w-p 860c0000 00:00 0
860c7000-860ca000 rw-p 860c7000 00:00 0
860ca000-860cd000 r--p 860ca000 00:00 0
860e2000-860e4000 rw-p 860e2000 00:00 0
860ec000-860f0000 r--p 860ec000 00:00 0
860f3000-860f8000 ---p 860f3000 00:00 0
I can't see how this can show performance differences but I'm not sure
what other
part of the output is relevant.  Should I run it with some other options?
Thanks,
Daniel
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