From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262739AbVAFFop (ORCPT ); Thu, 6 Jan 2005 00:44:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262741AbVAFFop (ORCPT ); Thu, 6 Jan 2005 00:44:45 -0500 Received: from smtp207.mail.sc5.yahoo.com ([216.136.129.97]:21429 "HELO smtp207.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S262739AbVAFFon (ORCPT ); Thu, 6 Jan 2005 00:44:43 -0500 Message-ID: <41DCD047.9050707@yahoo.com.au> Date: Thu, 06 Jan 2005 16:44:39 +1100 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20041007 Debian/1.7.3-5 X-Accept-Language: en MIME-Version: 1.0 To: Andrea Arcangeli CC: Andrew Morton , riel@redhat.com, marcelo.tosatti@cyclades.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH][5/?] count writeback pages in nr_scanned References: <20050105173624.5c3189b9.akpm@osdl.org> <41DCB577.9000205@yahoo.com.au> <20050105202611.65eb82cf.akpm@osdl.org> <41DCC014.80007@yahoo.com.au> <20050105204706.0781d672.akpm@osdl.org> <20050106045932.GN4597@dualathlon.random> <20050105210539.19807337.akpm@osdl.org> <20050106051707.GP4597@dualathlon.random> <41DCCA68.3020100@yahoo.com.au> <20050106052507.GR4597@dualathlon.random> <41DCCE53.4000906@yahoo.com.au> In-Reply-To: <41DCCE53.4000906@yahoo.com.au> 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 Nick Piggin wrote: > Andrea Arcangeli wrote: > >> On Thu, Jan 06, 2005 at 04:19:36PM +1100, Nick Piggin wrote: >> >>> This is practically what blk_congestion_wait does when the queue >>> isn't congested though, isn't it? >> >> >> >> The fundamental difference that makes it reliable is that: >> >> 1) only the I/O we're throttling against will be considered for the >> wakeup event, which means only clearing PG_writeback will be >> considered eligible for wakeup >> Currently _all_ unrelated write I/O was considered eligible >> for wakeup events and that could cause spurious oom kills. > > > I'm not entirely convinced. In Rik's case it didn't matter, because > all his writeout was in the same zone that reclaim was happening > against (ZONE_NORMAL), so in that case, PG_writeback throttling > will do exactly the same thing as blk_congestion_wait. > > I do like your PG_writeback throttling idea for the other reason > that it should behave better on NUMA systems with lots of zones > and lots of disks. > ... or Andrew's described fix. I think both would result in pretty similar behaviour, but Andrew's is probably a bit nicer because it doesn't require the scanner to have initiated the write.