From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932212AbXCUPYk (ORCPT ); Wed, 21 Mar 2007 11:24:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932184AbXCUPYk (ORCPT ); Wed, 21 Mar 2007 11:24:40 -0400 Received: from x35.xmailserver.org ([64.71.152.41]:33856 "EHLO x35.xmailserver.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932212AbXCUPYj (ORCPT ); Wed, 21 Mar 2007 11:24:39 -0400 X-AuthUser: davidel@xmailserver.org Date: Wed, 21 Mar 2007 08:23:56 -0700 (PDT) From: Davide Libenzi X-X-Sender: davide@alien.or.mcafeemobile.com To: Jens Axboe cc: Linux Kernel Mailing List , Ingo Molnar , Linus Torvalds Subject: Re: AIO, FIO and Threads ... In-Reply-To: <20070321074014.GD14389@kernel.dk> Message-ID: References: <20070321074014.GD14389@kernel.dk> X-GPG-FINGRPRINT: CFAE 5BEE FD36 F65E E640 56FE 0974 BF23 270F 474E X-GPG-PUBLIC_KEY: http://www.xmailserver.org/davidel.asc MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 21 Mar 2007, Jens Axboe wrote: > On Tue, Mar 20 2007, Davide Libenzi wrote: > > > > I was looking at Jens FIO stuff, and I decided to cook a quick patch for > > FIO to support GUASI (Generic Userspace Asyncronous Syscall Interface): > > > > http://www.xmailserver.org/guasi-lib.html > > > > I then ran a few tests on my Dual Opteron 252 with SATA drives (sata_nv) > > and 8GB of RAM. > > Mind that I'm not FIO expert, like at all, but I got some interesting > > results when comparing GUASI with libaio at 8/1000/10000 depths. > > If I read those result correctly (Jens may help), GUASI output is more > > then double the libaio one. > > Lots of context switches, yes. But the throughput looks like 2+ times. > > Can someone try to repeat the measures and/or spot the error? > > Or tell me which other tests to run? > > This is kinda a suprise for me ... > > I don't know guasi at all, but libaio requires O_DIRECT to be async. I'm > sure you know this, but you may not know that fio default to buffered IO > so you have to tell it to use O_DIRECT :-) > > So try adding a --direct=1 (or --buffered=0, same thing) as an extra > option when comparing depths > 1. I knew about AIO and O_DIRECT, but I thought FIO was using it by default :) I used it for the first time yesterday night, and there are a pretty wide set of options. Will re-run today with --direct. I was pretty surprised though. Since libaio was matching with syslets, I was thinking that a userspace version using a queue-always design (hard to do the cachehit optimization if you're not inside the scheduler ;), was going to be considerably slower. > I'll add your guasi engine, but disable it. Unfortunately fio still > doesn't have a nifty configure setup, so these things are still > manual... Well, you do have your own HAVE_*, you just need to make autoconf/automake do the checks for you. Of course, then you'll be pissed every time an autoconf/automake update break your setup, but lately it seems to be going better. Really :) - Davide