linux-kernel - Re: missing madvise functionality

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20070403225155.GA26567@one.firstfloor.org>
Date:	Wed, 4 Apr 2007 00:51:55 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Ulrich Drepper <drepper@...hat.com>
Cc:	Eric Dumazet <dada1@...mosbay.com>, 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

On Tue, Apr 03, 2007 at 02:46:09PM -0700, Ulrich Drepper wrote:
> 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.

If you know in advance you need them it might be possible to 
batch that. e.g. MADV_WILLNEED could be extended to
work on anonymous memory and establish the mappings in the syscall. 
Would that be useful? 

-Andi
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/