From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264085AbUECWBp (ORCPT ); Mon, 3 May 2004 18:01:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264088AbUECWBp (ORCPT ); Mon, 3 May 2004 18:01:45 -0400 Received: from mailgate2.mysql.com ([213.136.52.47]:23515 "EHLO mailgate.mysql.com") by vger.kernel.org with ESMTP id S264085AbUECWBm (ORCPT ); Mon, 3 May 2004 18:01:42 -0400 Subject: Re: Random file I/O regressions in 2.6 From: Peter Zaitsev To: Ram Pai Cc: Andrew Morton , nickpiggin@yahoo.com.au, alexeyk@mysql.com, linux-kernel@vger.kernel.org, axboe@suse.de In-Reply-To: <1083621052.7949.53.camel@localhost.localdomain> References: <200405022357.59415.alexeyk@mysql.com> <409629A5.8070201@yahoo.com.au> <20040503110854.5abcdc7e.akpm@osdl.org> <1083615727.7949.40.camel@localhost.localdomain> <20040503135719.423ded06.akpm@osdl.org> <1083620245.23042.107.camel@abyss.local> <1083621052.7949.53.camel@localhost.localdomain> Content-Type: text/plain Organization: MySQL Message-Id: <1083621680.23040.120.camel@abyss.local> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Mon, 03 May 2004 15:01:21 -0700 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2004-05-03 at 14:50, Ram Pai wrote: > > Looking at it the other way, without readahead code, all requests > satisfied through 4k i/os. Readahead helps in generating larger size > i/os. Huh, This is kind of really strange. If you speak about database world, Random IO is quite frequent and database page sizes are normally larger than OS page size. Furthermore even if it is split to 4K block sizes, why are they not submitted in parallel, being merged on lower level. Anyway we seems to all agree this is not very good behavior and it should be fixed :) -- Peter Zaitsev, Senior Support Engineer MySQL AB, www.mysql.com