Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754885Ab0KCKur (ORCPT ); Wed, 3 Nov 2010 06:50:47 -0400 Received: from mtagate7.uk.ibm.com ([194.196.100.167]:54416 "EHLO mtagate7.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754344Ab0KCKuo (ORCPT ); Wed, 3 Nov 2010 06:50:44 -0400 Message-ID: <4CD13E7B.5090804@linux.vnet.ibm.com> Date: Wed, 03 Nov 2010 11:50:35 +0100 From: Christian Ehrhardt User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.15) Gecko/20101027 Thunderbird/3.0.10 MIME-Version: 1.0 To: Mel Gorman CC: Andrew Morton , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Linux Kernel List , Johannes Weiner , Minchan Kim , Wu Fengguang , KAMEZAWA Hiroyuki , KOSAKI Motohiro Subject: Re: [PATCH 0/8] Reduce latencies and improve overall reclaim efficiency v2 References: <1284553671-31574-1-git-send-email-mel@csn.ul.ie> <4CB721A1.4010508@linux.vnet.ibm.com> <20101018135535.GC30667@csn.ul.ie> In-Reply-To: <20101018135535.GC30667@csn.ul.ie> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2741 Lines: 47 On 10/18/2010 03:55 PM, Mel Gorman wrote: > On Thu, Oct 14, 2010 at 05:28:33PM +0200, Christian Ehrhardt wrote: > >> Seing the patches Mel sent a few weeks ago I realized that this series >> might be at least partially related to my reports in 1Q 2010 - so I ran my >> testcase on a few kernels to provide you with some more backing data. > > Thanks very much for revisiting this. > >> Results are always the average of three iozone runs as it is known to be somewhat noisy - especially when affected by the issue I try to show here. >> As discussed in detail in older threads the setup uses 16 disks and scales the number of concurrent iozone processes. >> Processes are evenly distributed so that it always is one process per disk. >> In the past we reported 40% to 80% degradation for the sequential read case based on 2.6.32 which can still be seen. >> What we found was that the allocations for page cache with GFP_COLD flag loop a long time between try_to_free, get_page, reclaim as free makes some progress and due to that GFP_COLD allocations can loop and retry. >> In addition my case had no writes at all, which forced congestion_wait to wait the full timeout all the time. >> >> Kernel (git) 4 8 16 deviation #16 case comment >> linux-2.6.30 902694 1396073 1892624 base base >> linux-2.6.32 752008 990425 932938 -50.7% impact as reported in 1Q 2010 >> linux-2.6.35 63532 71573 64083 -96.6% got even worse >> linux-2.6.35.6 176485 174442 212102 -88.8% fixes useful, but still far away >> linux-2.6.36-rc4-trace 119683 188997 187012 -90.1% still bad >> linux-2.6.36-rc4-fix 884431 1114073 1470659 -22.3% Mels fixes help a lot! >> [...] > If all goes according to plan, > kernel 2.6.37-rc1 will be of interest. Thanks again. Here a measurement with 2.6.37-rc1 as confirmation of progress: linux-2.6.37-rc1 876588 1161876 1643430 -13.1% even better than 2.6.36-fix That means 2.6.37-rc1 really shows what we hoped for. And it eventually even turned out a little bit better than 2.6.36 + your fixes. -- Gr?sse / regards, Christian Ehrhardt IBM Linux Technology Center, System z Linux Performance -- 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/