Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759817AbZDCBzc (ORCPT ); Thu, 2 Apr 2009 21:55:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755581AbZDCBzX (ORCPT ); Thu, 2 Apr 2009 21:55:23 -0400 Received: from mail-gx0-f160.google.com ([209.85.217.160]:62040 "EHLO mail-gx0-f160.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753041AbZDCBzW convert rfc822-to-8bit (ORCPT ); Thu, 2 Apr 2009 21:55:22 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=nKMPx7jj6L5nFsd9Lu5A4LB3Ey5779LzezTQKhf6zKRWfKFmDQNO/HAjyRfumOHc9E KYZC2F2aBfl+J/xf/S+JVnndVl7zAeL9fCGTWjEGf1TUnPHAyQH6zwWW23rHyPfv9rBr guu8I2PspDHjo5hzV4IFnKE/kUacp6QtpBZow= MIME-Version: 1.0 In-Reply-To: <9b1675090904021728y35776377u327f2266d06e2f29@mail.gmail.com> References: <49CCCB0A.6070701@nokia.com> <9b1675090904021724t2fb0a671uc10d8e7bcba0bc5c@mail.gmail.com> <9b1675090904021728y35776377u327f2266d06e2f29@mail.gmail.com> Date: Thu, 2 Apr 2009 18:55:03 -0700 Message-ID: <72dbd3150904021855v440f46a7oc21a7ed28fbfcb13@mail.gmail.com> Subject: Re: EXT4-ish "fixes" in UBIFS From: David Rees To: "Trenton D. Adams" Cc: Christian Kujau , Artem Bityutskiy , Linux Kernel Mailing List Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1947 Lines: 43 On Thu, Apr 2, 2009 at 5:28 PM, Trenton D. Adams wrote: > On Thu, Apr 2, 2009 at 6:24 PM, Trenton D. Adams > wrote: >> Yes, mounting "-o sync" does improve ext3 performance. ?It sucks >> though, because I do want quick writes. ?And mounting with sync option >> slows down to disk io speeds. ?In my case, that's between 20 and 23 >> megabytes per second *big frown, quivering lip, and tears in my eyes*. >> :P >> > > Oh, I should have clarified. ?It improves performance under heavy > load. ?Under normal load, mounting without sync is fine. ?What I tend > to do is mount with "remount,rw,sync" when heavy load is starting. > Then my system goes slowly, but latency is good. ?Then, when it's all > done (say a big compile, or job, or whatever), I remount without sync > again. > > I'm thinking of writing a script that monitors performance, and > remounts as needed, lol. ?WHAT A HACK. hehe. All you're doing here is implementing the lowering of dirty data limits in the VM dynamically based on how long fsyncs take. Linus outlined this specific strategy as "the ideal siutation" somewhere in the depths of "That filesystem thread". Look at the new in 2.6.29 dirty*bytes parameters in Documentation/sysctl/vm.txt for more info. By lowering those values, you can effectively turn normal writes into synchronous writes which will greatly reduce latency of fsync under heavy write load. In previous kernels you can tweak dirty_ratio and dirty_background_ratio, but they don't have the granularity of the new knobs. Although if you are talking about just remounting in sync mode, they may work for you at least as a proof of concept. ;-) -Dave -- 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/