linux-kernel - Re: [PATCH] lazy freeing of memory through MADV

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Date:	Mon, 23 Apr 2007 07:45:56 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Nick Piggin <nickpiggin@...oo.com.au>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>, shak <dshaks@...hat.com>,
	jakub@...hat.com, drepper@...hat.com
Subject: Re: [PATCH] lazy freeing of memory through MADV_FREE

Rik van Riel wrote:

> First some ebizzy runs...

This is interesting.  Ginormous speedups in ebizzy[1] on my quad core
test system.  The following numbers are the average of 10 runs, since
ebizzy shows some variability.

You can see a big influence from the tlb batching and from Nick's
madv_sem patch.  The reduction in system time from 100 seconds to
3 seconds is way more than I had expected, but I'm not complaining.
The 4 fold reduction in wall clock time is a nice bonus.

According to Val, ebizzy shows the weaknesses of Linux with a real
workload, so this could be a useful result.

kernel
                    user     system     wall clock    %CPU

vanilla             186s    101s       123s          230%
madv_free (madv)    175s     96s       120s          230%
mmap_sem (sem)      100s     40s        40s          370%
madv+sem            200s    140s       100s          393%
madv+sem+tlb        118s      3s        30s          395%
madv+tlb            150s     10s        50s          310%

[1] http://www.ussg.iu.edu/hypermail/linux/kernel/0604.2/1699.html
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