From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id B10C56B0139 for ; Fri, 12 Mar 2010 07:15:22 -0500 (EST) Received: from d06nrmr1407.portsmouth.uk.ibm.com (d06nrmr1407.portsmouth.uk.ibm.com [9.149.38.185]) by mtagate7.uk.ibm.com (8.13.1/8.13.1) with ESMTP id o2CCFJZg003168 for ; Fri, 12 Mar 2010 12:15:19 GMT Received: from d06av03.portsmouth.uk.ibm.com (d06av03.portsmouth.uk.ibm.com [9.149.37.213]) by d06nrmr1407.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o2CCF95T606256 for ; Fri, 12 Mar 2010 12:15:19 GMT Received: from d06av03.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av03.portsmouth.uk.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id o2CCF9Or013525 for ; Fri, 12 Mar 2010 12:15:09 GMT Message-ID: <4B9A3049.7010602@linux.vnet.ibm.com> Date: Fri, 12 Mar 2010 13:15:05 +0100 From: Christian Ehrhardt MIME-Version: 1.0 Subject: Re: [RFC PATCH 0/3] Avoid the use of congestion_wait under zone pressure References: <1268048904-19397-1-git-send-email-mel@csn.ul.ie> <20100311154124.e1e23900.akpm@linux-foundation.org> <4B99E19E.6070301@linux.vnet.ibm.com> <20100312020526.d424f2a8.akpm@linux-foundation.org> <20100312104712.GB18274@csn.ul.ie> In-Reply-To: <20100312104712.GB18274@csn.ul.ie> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Andrew Morton , linux-mm@kvack.org, Nick Piggin , Chris Mason , Jens Axboe , linux-kernel@vger.kernel.org List-ID: Mel Gorman wrote: > On Fri, Mar 12, 2010 at 02:05:26AM -0500, Andrew Morton wrote: >> On Fri, 12 Mar 2010 07:39:26 +0100 Christian Ehrhardt wrote: >> >>> >>> Andrew Morton wrote: >>>> On Mon, 8 Mar 2010 11:48:20 +0000 >>>> Mel Gorman wrote: [...] >> If not, we broke it again. >> > > We were broken with respect to this in the first place. That > cond_reched() is badly placed and waiting on congestion when congestion > might not be involved is also a bit odd. > > It's possible that Christian's specific problem would also be addressed > by the following patch. Christian, willing to test? Will is here, but no chance before monday/tuesday to get a free machine slot - I'll post results as soon as I get them. > It still feels a bit unnatural though that the page allocator waits on > congestion when what it really cares about is watermarks. Even if this > patch works for Christian, I think it still has merit so will kick it a > few more times. In whatever way I can look at it watermark_wait should be supperior to congestion_wait. Because as Mel points out waiting for watermarks is what is semantically correct there. If there eventually some day comes a solution without any of those waits I'm fine too - e.g. by closing whatever races we have and fixing that one context can never run into this in direct_reclaim: 1. free pages with try_to_free 2. not getting one in the subsequent get_page call But as long as we have a wait - watermark waiting > congestion waiting (IMHO). > ==== CUT HERE ==== > page-allocator: Attempt page allocation immediately after direct reclaim [...] -- Grusse / regards, Christian Ehrhardt IBM Linux Technology Center, System z Linux Performance -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org