From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 8 Aug 2001 14:14:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 8 Aug 2001 14:14:25 -0400 Received: from [63.209.4.196] ([63.209.4.196]:41481 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id ; Wed, 8 Aug 2001 14:14:16 -0400 To: linux-kernel@vger.kernel.org From: torvalds@transmeta.com (Linus Torvalds) Subject: Re: I/O very slow under 2.4 (device reading) Date: Wed, 8 Aug 2001 18:12:40 +0000 (UTC) Organization: Transmeta Corporation Message-ID: <9krveo$82c$1@penguin.transmeta.com> In-Reply-To: <20010808193158.A4055@cerebro.laendle> X-Trace: palladium.transmeta.com 997294425 26750 127.0.0.1 (8 Aug 2001 18:13:45 GMT) X-Complaints-To: news@transmeta.com NNTP-Posting-Date: 8 Aug 2001 18:13:45 GMT Cache-Post-Path: palladium.transmeta.com!unknown@penguin.transmeta.com X-Cache: nntpcache 2.4.0b5 (see http://www.nntpcache.org/) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org In article <20010808193158.A4055@cerebro.laendle>, wrote: >It might be vm related, it might be not, but I get very funny effects when >running: > > buffer -S1m -s128k -m32m /dev/null > >(buffer is just a fast read/write buffer reading stdin to stdout, i use it >to check wether all sectors of a disk are readable, it's similar to dd, >which creates the same effects). I bet it's the same thing that made writes slow - the buffer allocator and the VM disagree about how/when to allocate memory. It's fixed by the patch that's floating around in the "VM suckage" thread along with the tweak to fix "zone_free_plenty()". I'll make a real pre-patch (2.4.8-pre7) with the full changeset, can you test that out? I did an equivalent "dd" that you see problems with, and on my current kernel as long as there isn't other IO activity it stays at a nice stable 21MB/s which is all my disk can deliver. [ Damn, maybe I should get one of those nice big 7200 rpm IBM drives ] Linus