linux-kernel - Re: missing madvise functionality

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Message-ID: <4612CB21.9020005@redhat.com>
Date:	Tue, 03 Apr 2007 14:46:09 -0700
From:	Ulrich Drepper <drepper@...hat.com>
To:	Eric Dumazet <dada1@...mosbay.com>
CC:	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Jakub Jelinek <jakub@...hat.com>, linux-mm@...ck.org,
	Hugh Dickins <hugh@...itas.com>
Subject: Re: missing madvise functionality

Eric Dumazet wrote:
> A page fault is not that expensive. But clearing N*PAGE_SIZE bytes is,
> because it potentially evicts a large part of CPU cache.

*A* page fault is not that expensive.  The problem is that you get a
page fault for every single page.  For 200k allocated you get 50 page
faults.  It quickly adds up.

-- 
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖


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