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

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Message-ID: <20090201130058.GA486@elte.hu>
Date:	Sun, 1 Feb 2009 14:00:58 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Daniel Lowengrub <lowdanie@...il.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2.6.28 1/2] memory: improve find_vma


* Daniel Lowengrub <lowdanie@...il.com> wrote:

> 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?

you should time it:

 time ./mmap-perf

and compare the before/after results.

	Ingo
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