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 13:32:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 8 Aug 2001 13:32:09 -0400 Received: from islay.mach.uni-karlsruhe.de ([129.13.162.92]:20655 "EHLO mailout.plan9.de") by vger.kernel.org with ESMTP id ; Wed, 8 Aug 2001 13:31:59 -0400 Date: Wed, 8 Aug 2001 19:31:58 +0200 From: To: linux-kernel@vger.kernel.org Subject: I/O very slow under 2.4 (device reading) Message-ID: <20010808193158.A4055@cerebro.laendle> Mail-Followup-To: linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Operating-System: Linux version 2.4.8-pre4 (root@cerebro) (gcc version 3.0.1 20010716 (prerelease)) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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). The problem is that under 2.4.4, 2.4.5 and 2.4.8pre4, the machine first reads at about 30mb/s. then, after a few minutes, it stops for small amounts of time, and, even worse, the system becomes totally sluggish, even unusable for parts of seconds or even a second (mouse doesn't move, programs need ages to starte etc...) Then, after quite some time this behaviour stops, and the command reads only very very slowly: procs memory swap io system cpu r b w swpd free buff cache si so bi bo in cs us sy id 1 0 0 0 3168 327504 51964 0 0 256 0 123 704 0 46 54 2 0 0 0 3168 327504 51964 0 0 256 0 333 1167 0 51 49 1 0 0 0 3168 327504 51964 0 0 256 6 141 740 0 50 50 2 0 0 0 3172 327500 51964 0 0 256 0 110 661 0 50 50 1 0 0 0 3128 327548 51960 0 0 8512 44 470 1595 0 45 55 1 0 0 0 3128 327544 51960 0 0 256 2 394 2071 3 51 46 1 0 0 0 3124 327544 51960 0 0 320 0 164 798 0 50 50 1 0 0 0 3124 327540 51964 0 0 256 8 121 743 0 50 50 1 0 0 0 3124 327540 51964 0 0 1280 0 176 826 0 50 50 1 0 1 0 3120 327544 51964 0 0 320 64 201 858 0 50 50 as you can see, it reads about 256k/s only, but requires 100% cpu (it's a dual cpu system and idle == 50 means one cpu is tied up): CPU1 states: 0.0% user, 100.0% system, 0.0% nice, 0.0% idle Tied up in the kernel, btw. the rest of the system works and is fast. hdparm reports nothing spectacular: /dev/hde: multcount = 16 (on) I/O support = 1 (32-bit) unmaskirq = 1 (on) using_dma = 1 (on) keepsettings = 1 (on) nowerr = 0 (off) readonly = 0 (off) readahead = 8 (on) geometry = 53614/16/63, sectors = 120103200, start = 0 and indeed the disk is still fast: cerebro:~# hdparm -tT /dev/hde /dev/hde: Timing buffer-cache reads: 128 MB in 0.76 seconds =168.42 MB/sec Timing buffered disk reads: 64 MB in 1.78 seconds = 35.96 MB/sec this is, btw, WHILE the above buffer command was still running. any ideas how to proceed with this problem? -- -----==- | ----==-- _ | ---==---(_)__ __ ____ __ Marc Lehmann +-- --==---/ / _ \/ // /\ \/ / pcg@goof.com |e| -=====/_/_//_/\_,_/ /_/\_\ XX11-RIPE --+ The choice of a GNU generation | |