linux-kernel - Re: missing madvise functionality

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Date:	Thu, 05 Apr 2007 03:39:29 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Rik van Riel <riel@...hat.com>
CC:	Jakub Jelinek <jakub@...hat.com>,
	Ulrich Drepper <drepper@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-mm@...ck.org, Hugh Dickins <hugh@...itas.com>
Subject: Re: missing madvise functionality

Rik van Riel wrote:

> MADV_DONTNEED, unpatched, 1000 loops
> 
> real    0m13.672s
> user    0m1.217s
> sys     0m45.712s
> 
> 
> MADV_DONTNEED, with patch, 1000 loops
> 
> real    0m4.169s
> user    0m2.033s
> sys     0m3.224s

I just noticed something fun with these numbers.

Without the patch, the system (a quad core CPU) is 10% idle.

With the patch, it is 66% idle - presumably I need Nick's
mmap_sem patch.

However, despite being 66% idle, the test still runs over
3 times as fast!

-- 
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