Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756248AbZDCC0S (ORCPT ); Thu, 2 Apr 2009 22:26:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752069AbZDCC0G (ORCPT ); Thu, 2 Apr 2009 22:26:06 -0400 Received: from wf-out-1314.google.com ([209.85.200.171]:60596 "EHLO wf-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751043AbZDCC0D convert rfc822-to-8bit (ORCPT ); Thu, 2 Apr 2009 22:26:03 -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=HHDDPnvAxWsHUbPlzHm6L9PnMCnti8qT6qtl7QPCt+s9CVIrBO1iWRQ9vfBDKxL7Io 73IeD7uG3CQGQmJ7wN2MYJO2fdfSEYftLWB9SMUnluCdIBWbAteatBXLk3PY1cnWaXKa aFfzao8S+6iv5CJsoKoncXH7Gq0VRA6breOOU= MIME-Version: 1.0 In-Reply-To: <72dbd3150904021855v440f46a7oc21a7ed28fbfcb13@mail.gmail.com> References: <49CCCB0A.6070701@nokia.com> <9b1675090904021724t2fb0a671uc10d8e7bcba0bc5c@mail.gmail.com> <9b1675090904021728y35776377u327f2266d06e2f29@mail.gmail.com> <72dbd3150904021855v440f46a7oc21a7ed28fbfcb13@mail.gmail.com> Date: Thu, 2 Apr 2009 20:26:01 -0600 Message-ID: <9b1675090904021926o4a404c3ajf623b1560f919289@mail.gmail.com> Subject: Re: EXT4-ish "fixes" in UBIFS From: "Trenton D. Adams" To: David Rees 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: 2133 Lines: 43 On Thu, Apr 2, 2009 at 7:55 PM, David Rees wrote: > 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. WOW, that makes a huge difference. If I set it to 100M, I get the 10-15 second delay I was talking about. But, if I set it to 1M, I get 0.3 to 0.4 second delay on a 1M fsync. That is way better. Perhaps I should auto-tune based on that parameter then. Although I do agree with Linus that it sucks to do userland auto-tuning. :P -- 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/