Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 9 Oct 2002 21:04:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 9 Oct 2002 21:04:10 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.106]:61602 "EHLO e6.ny.us.ibm.com") by vger.kernel.org with ESMTP id ; Wed, 9 Oct 2002 21:04:06 -0400 Message-ID: <3DA4D34F.3070106@us.ibm.com> Date: Wed, 09 Oct 2002 18:09:35 -0700 From: Dave Hansen User-Agent: Mozilla/5.0 (compatible; MSIE5.5; Windows 98; X-Accept-Language: en-us, en MIME-Version: 1.0 To: Andrew Morton CC: linux-kernel@vger.kernel.org, Rik van Riel Subject: Degraded I/O performance, since 2.5.41 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1923 Lines: 48 When I run a certain large webserver benchmark, I prefer to warm the pagecache up with the file set first, to cheat a little :) I grep through 20 different 500MB file sets in parallel to do this. It is a _lot_ slower in the BK snapshot than in plain 2.5.41. And, no, these numbers aren't inflated, I have a lot of fast disks. I _can_ do 50MB/sec :) A little snipped from vmstat (I cut out the boring columns): good kernel: 2.5.41: vmstat 4 Cached bi bo bi cs us s id 389280 53284 7 1625 3235 12 88 0 600580 53489 19 1599 3264 11 89 0 813428 53891 0 1587 3256 12 88 0 1027260 54093 0 1609 3239 12 88 0 1241448 54183 0 1611 3251 11 89 0 1454036 53790 0 1618 3267 12 88 0 doing the entire 10GB grep takes 192 seconds. a dd produces: ~48000 bi/sec exact same grep operation on kernel: 2.5.41+yesterday's bk: vmstat 4 Cached bi bo bi cs us sy id 4855948 9697 1 1408 846 20 80 0 4890464 8745 0 1398 800 18 82 0 4922392 8077 55 1364 676 21 79 0 4959164 9296 1 1399 798 18 82 0 4995936 9315 0 1407 830 19 81 0 5027208 7931 0 1351 638 22 78 0 5066256 9855 9 1416 856 19 81 0 I was too impatient to wait on the greps to complete. a dd produces: ~37800 bi/sec So, bi/sec goes from 54,000 in 2.5.41, to ~8700 in yesterday's snapshot. It goes from around 50MB/sec to about 8MB/sec. Although vmstat shows 0% idle time, the profilers show lots of idle time, 98%! I tried oprofile and readprofile. Is the 2.0.9 vmstat still broken? I'm using idle=poll if that makes any difference. -- Dave Hansen haveblue@us.ibm.com - 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/