Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760777AbZDFWVa (ORCPT ); Mon, 6 Apr 2009 18:21:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760661AbZDFWVH (ORCPT ); Mon, 6 Apr 2009 18:21:07 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:33557 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755922AbZDFWVF (ORCPT ); Mon, 6 Apr 2009 18:21:05 -0400 Date: Mon, 6 Apr 2009 15:17:28 -0700 (PDT) From: Linus Torvalds X-X-Sender: torvalds@localhost.localdomain To: Ray Lee cc: Hua Zhong , Theodore Tso , Jens Axboe , Linux Kernel Mailing List Subject: Re: [PATCH 0/8][RFC] IO latency/throughput fixes In-Reply-To: <2c0942db0904061504l6504934bi446f7425fcd38470@mail.gmail.com> Message-ID: References: <1239022088-29002-1-git-send-email-jens.axboe@oracle.com> <20090406151054.GD5178@kernel.dk> <20090406183157.GD7376@mit.edu> <002501c9b6f3$f85b4910$e911db30$@com> <20090406211931.GB8586@mit.edu> <003001c9b6ff$a9259ce0$fb70d6a0$@com> <2c0942db0904061504l6504934bi446f7425fcd38470@mail.gmail.com> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1628 Lines: 37 On Mon, 6 Apr 2009, Ray Lee wrote: > > Your argument seems to be that someone may be relying upon default > kernel behavior and, at the same time, is willing to continually > upgrade their kernel. No, I do think that the argument is valid per se: the crash behavior of "data=ordered" wrt "data=writeback" _is_ very different. And it's true that "data=ordered" has nicer behavior in the case of a crash. But it is also true that with all the recent patches, "data=writeback" has become a _lot_ more attractive. It is slightly more ordered than it used to be, in a very particular way that makes one of the biggest downsides go away. And the latency improvements are really quite stunning (*). So I think Hua's argument is real, but at the same time we should balance it against the fact that a lot of people will just use whatever is the default - and as a result we should strive to make the default be the thing that we think people would be happiest with. I think "ordered" was a reasonable default, but that was at least partly because _both_ ordered and writeback sucked (partly in different ways). I do think we could make it a config option. Linus (*) Admittedly with a very specific workload, but I suspect it's not that uncommon, and there will be people who never realized what their problem was and blamed jerky behavior on scheduler or something. -- 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/