From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id B7E246B0047 for ; Mon, 13 Sep 2010 15:09:56 -0400 (EDT) Received: by qwf7 with SMTP id 7so4876323qwf.14 for ; Mon, 13 Sep 2010 12:09:54 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20100913152138.GA16334@sig21.net> References: <20100907133429.GB3430@sig21.net> <20100909120044.GA27765@sig21.net> <20100910120235.455962c4@schatten.dmk.lab> <20100910160247.GA637@sig21.net> <20100913152138.GA16334@sig21.net> From: dave b Date: Tue, 14 Sep 2010 05:09:31 +1000 Message-ID: Subject: Re: block cache replacement strategy? Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org To: Johannes Stezenbach Cc: Florian Mickler , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org List-ID: On 14 September 2010 01:21, Johannes Stezenbach wrote: > On Fri, Sep 10, 2010 at 06:02:48PM +0200, Johannes Stezenbach wrote: >> >> Linear read heuristic might be a good guess, but it would >> be nice to hear a comment from a vm/fs expert which >> confirms this works as intended. > > Apparently I'm unworthy to get a response from someone knowledgable :-( > > Anyway I found lmdd (from lmbench) can do random reads, > and indeed causes the data to enter the block (page?) cache, > replacing the previous data. I am no expert, but what did you think would happen if you did dd twice from /dev/zero? but... Honestly what do you think will be cached? If you want 'COW', use btrfs. -- Conscience doth make cowards of us all. -- Shakespeare -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org