Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752646AbZDGFYU (ORCPT ); Tue, 7 Apr 2009 01:24:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751911AbZDGFYJ (ORCPT ); Tue, 7 Apr 2009 01:24:09 -0400 Received: from wf-out-1314.google.com ([209.85.200.171]:12903 "EHLO wf-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751711AbZDGFYI (ORCPT ); Tue, 7 Apr 2009 01:24:08 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:references:in-reply-to:subject:date:message-id :mime-version:content-type:content-transfer-encoding:x-mailer :thread-index:content-language; b=U0ByxUKLTTE6WyH+jJa2gSFMtZEzbtEyge+wsE3o6pdoMqO0Mq6EYZTWU4cARwMeVk 71aTdJ5hLm5+LpUoLiDCB5v8/ZVbJAQ5Ao7t6oopkQ8e4l1Czi4C1+zvXCkyux+aPMQa ZRU4Vy9h5l5Hg2L6lwZFsofnb4H9U60ULbCqo= From: "Hua Zhong" To: "'Linus Torvalds'" , "'Trenton D. Adams'" Cc: "'Chris Mason'" , "'Theodore Tso'" , "'Jens Axboe'" , "'Linux Kernel Mailing List'" 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> <1239076379.17426.23.camel@think.oraclecorp.com> <9b1675090904062113r2bd2b209hea1061cc54a0b9c0@mail.gmail.com> <9b1675090904062148k7081be9bs26b5852d71a0a45c@mail.gmail.com> In-Reply-To: Subject: RE: [PATCH 0/8][RFC] IO latency/throughput fixes Date: Mon, 6 Apr 2009 22:23:31 -0700 Message-ID: <006f01c9b741$00c70510$02550f30$@com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook 12.0 Thread-Index: Acm3Po5M4qfoe24fTje4bWI/KGVbNwAATisw Content-Language: en-us Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3094 Lines: 81 The (small) set of people that rely on "ordered" understand the problem, as long as they are aware of the change (no, I don't think reading through all changelogs from their old kernel to the new one is a realistic option). So a config option should be good enough to get them to notice the change (I assume a missing default will force them to choose an option), and therefore explicitly add the -o ordered option to their scripts. On the other hand a run-time tunable has no real point. > -----Original Message----- > From: Linus Torvalds [mailto:torvalds@linux-foundation.org] > Sent: Monday, April 06, 2009 10:02 PM > To: Trenton D. Adams > Cc: Chris Mason; Theodore Tso; Hua Zhong; Jens Axboe; Linux Kernel > Mailing List > Subject: Re: [PATCH 0/8][RFC] IO latency/throughput fixes > > > > On Mon, 6 Apr 2009, Trenton D. Adams wrote: > > > > What about a procfs setting instead? Is there a policy about why > > something should be in procfs or /sys, or as a kernel config option? > > That's basically as small as the patch you just made, right? > > I'm never really against making things dynamically tunable, but this > already was, and that wasn't really the issue. > > Sure, you can just re-mount your filesystem with different options. > That's > what I did while testing - my /home is on a drive of its own, so I > would > just log out and as root unmount and re-mount with > data=ordered/writeback, > and log in and test again. > > So dynamic tuning is good. But at the same time, having a tuning option > is > _never_ an excuse for not getting the default right in the first place. > It's just a cop-out to say "hey, the default may be wrong for you, but > you > can always tune it locally with XYZ". > > The thing is, almost nobody does that. Partly because it needs effort > and > knowledge, partly because after a few years the number of tuning knobs > are > in the hundreds for every little thing. > > So instead, leave the tuning for the _really_ odd cases (if you use > your > machine as an IP router, you hopefully know enough to tune it if you > really care). Not for random general-purpose "use for whatever" kind of > thing. > > > I'm just thinking that something like this, where people want one > > thing or the other, but may not know it when they install Linux, > might > > like to change it realtime. Especially if they are a Linux newbie, > > and don't know how to compile their own kernel. Or don't have time > to > > maintain their own kernel installs. > > Oh absolutely. I'm not expecting people to compile their own kernels. > I'm > expecting that within a few months, most modern distributions will have > (almost by mistake) gotten a new set of saner defaults, and anybody who > keeps their machine up-to-date will see a smoother experience without > ever > even realizing _why_. > > Linus -- 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/