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 9AB806B009F for ; Fri, 10 Sep 2010 06:30:15 -0400 (EDT) Received: from list by lo.gmane.org with local (Exim 4.69) (envelope-from ) id 1Ou0rr-00013v-Rr for linux-mm@kvack.org; Fri, 10 Sep 2010 12:30:03 +0200 Received: from f053214237.adsl.alicedsl.de ([78.53.214.237]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 10 Sep 2010 12:30:03 +0200 Received: from florian by f053214237.adsl.alicedsl.de with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 10 Sep 2010 12:30:03 +0200 From: Florian Mickler Subject: Re: block cache replacement strategy? Date: Fri, 10 Sep 2010 12:02:35 +0200 Message-ID: <20100910120235.455962c4@schatten.dmk.lab> References: <20100907133429.GB3430@sig21.net> <20100909120044.GA27765@sig21.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit In-Reply-To: <20100909120044.GA27765@sig21.net> Sender: owner-linux-mm@kvack.org To: linux-mm@kvack.org Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org List-ID: On Thu, 9 Sep 2010 14:00:44 +0200 Johannes Stezenbach wrote: > On Tue, Sep 07, 2010 at 03:34:29PM +0200, Johannes Stezenbach wrote: > > > > during some simple disk read throughput testing I observed > > caching behaviour that doesn't seem right. The machine > > has 2G of RAM and AMD Athlon 4850e, x86_64 kernel but 32bit > > userspace, Linux 2.6.35.4. It seems that contents of the > > block cache are not evicted to make room for other blocks. > > (Or something like that, I have no real clue about this.) > > > > Since this is a rather artificial test I'm not too worried, > > but it looks strange to me so I thought I better report it. > > C'mon guys, please comment. Is this a bug or not? > Or is my question too silly? > > > Johannes Well I personally have no clue about the block caching, but perhaps that is an heuristic to prevent the cache from fluctuating too much? Some minimum time a block is hold... in a big linear read the cache is useless anyway most of the time, so it could make some sense... You could try accessing random files after filling up the cache and check if those evict the the cache. That should rule out any linear-read-detection heuristic. Cheers, Flo -- 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