Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932096AbZGPKia (ORCPT ); Thu, 16 Jul 2009 06:38:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755100AbZGPKi3 (ORCPT ); Thu, 16 Jul 2009 06:38:29 -0400 Received: from moutng.kundenserver.de ([212.227.17.8]:54024 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755090AbZGPKi2 (ORCPT ); Thu, 16 Jul 2009 06:38:28 -0400 Message-ID: <4A5F032F.40205@vlnb.net> Date: Thu, 16 Jul 2009 14:38:39 +0400 From: Vladislav Bolkhovitin User-Agent: Thunderbird 2.0.0.21 (X11/20090320) MIME-Version: 1.0 To: Kurt Garloff , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [RESEND] [PATCH] readahead:add blk_run_backing_dev References: <4A4DE3C1.5080307@vlnb.net> <4A51DC0A.10302@vlnb.net> <4A5238EC.1070505@vlnb.net> <4A5395FD.2040507@vlnb.net> <4A5493A8.2000806@vlnb.net> <20090715205220.GL31657@tpkurt2.suse.de> In-Reply-To: <20090715205220.GL31657@tpkurt2.suse.de> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V01U2FsdGVkX1+knSeD+lnSzxe1hgwr5IxkymRKFryEe/IeC3e KRY0tWiM0PSVZ8FnIIg1u1+y/xUXLpF5SwKyIfYsuUxXmqSJ6X j5WiN4j2XljNsWUCSG09w== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1056 Lines: 28 Kurt Garloff, on 07/16/2009 12:52 AM wrote: > Hi, > > On Wed, Jul 08, 2009 at 04:40:08PM +0400, Vladislav Bolkhovitin wrote: >> I've also long ago noticed that reading data from block devices is slower >> than from files from mounted on those block devices file systems. Can >> anybody explain it? > > Brainstorming: > - block size (reads on the block dev might be done with smaller size) As we already found out in this and other threads, smaller "block size", i.e. each request size, is often means better throughput, sometimes much better. > - readahead (do we use the same RA algo for block devs) > - page cache might be better optimized than buffer cache? > > Just guesses from someone that has not looked into that area of the > kernel for a while, so take it with a grain of salt. > > Cheers, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/