Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753413AbZDESzZ (ORCPT ); Sun, 5 Apr 2009 14:55:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751769AbZDESzK (ORCPT ); Sun, 5 Apr 2009 14:55:10 -0400 Received: from casper.infradead.org ([85.118.1.10]:38588 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751224AbZDESzI (ORCPT ); Sun, 5 Apr 2009 14:55:08 -0400 Date: Sun, 5 Apr 2009 11:56:29 -0700 From: Arjan van de Ven To: Linus Torvalds Cc: Theodore Tso , Jens Axboe , Linux Kernel Developers List , Ext4 Developers List Subject: Re: [GIT PULL] Ext3 latency fixes Message-ID: <20090405115629.521057fc@infradead.org> In-Reply-To: References: <20090404135719.GA9812@mit.edu> <20090404151649.GE5178@kernel.dk> <20090404173412.GF5178@kernel.dk> <20090404180108.GH5178@kernel.dk> <20090404232222.GA7480@mit.edu> <20090404163349.20df1208@infradead.org> <20090405001005.GA7553@mit.edu> Organization: Intel X-Mailer: Claws Mail 3.7.0 (GTK+ 2.14.7; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1301 Lines: 31 On Sun, 5 Apr 2009 10:01:06 -0700 (PDT) Linus Torvalds wrote: > Also, one of the issues seems to literally be that the higher-level > request handling doesn't care AT ALL about the priority. Allocating > the request itself does keep reads and writes separated, but if the > request is a SYNCIO request, and non-sync writes have filled up th > write requests, we'll have to wait for the background writes to free > up requests. > > That is quite possibly the longest wait we have in the system. it often is; latencytop tends to point that out. > > See get_request(): our default number of requests is so low that we very regularly hit the limit. In addition to setting kjournald to higher priority, I tend to set the number of requests to 4096 or so to improve interactive performance on my own systems. That way at least the elevator has a chance to see the requests ;-) -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- 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/