From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 5 Jul 2001 10:00:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 5 Jul 2001 10:00:15 -0400 Received: from penguin.e-mind.com ([195.223.140.120]:6916 "EHLO penguin.e-mind.com") by vger.kernel.org with ESMTP id ; Thu, 5 Jul 2001 09:59:58 -0400 Date: Thu, 5 Jul 2001 15:59:42 +0200 From: Andrea Arcangeli To: Alan Cox Cc: Dan Kegel , "linux-kernel@vger.kernel.org" Subject: Re: O_DIRECT please; Sybase 12.5 Message-ID: <20010705155942.P17051@athlon.random> In-Reply-To: <3B3C4CB4.6B3D2B2F@kegel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ; from alan@lxorguk.ukuu.org.uk on Fri, Jun 29, 2001 at 10:50:15AM +0100 X-GnuPG-Key-URL: http://e-mind.com/~andrea/aa.gnupg.asc X-PGP-Key-URL: http://e-mind.com/~andrea/aa.asc Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 29, 2001 at 10:50:15AM +0100, Alan Cox wrote: > > the boss say "If Linux makes Sybase go through the page cache on > > reads, maybe we'll just have to switch to Solaris. That's > > a serious performance problem." > > Thats something you'd have to benchmark. It depends on a very large number > of factors including whether the database uses mmap, the average I/O size > and the like correct, here the benchmarks: http://boudicca.tux.org/hypermail/linux-kernel/2001week17/1175.html http://boudicca.tux.org/hypermail/linux-kernel/2001week17/att-1175/01-directio.png of course the huge improvement is also because of broken VM in the buffered-io case. Andrea