From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Chinner Subject: Re: [PATCH] mm: disallow direct reclaim page writeback Date: Thu, 15 Apr 2010 16:20:55 +1000 Message-ID: <20100415062055.GQ2493@dastard> References: <20100414085132.GJ25756@csn.ul.ie> <20100415013436.GO2493@dastard> <20100415130212.D16E.A69D9226@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Mel Gorman , Chris Mason , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org To: KOSAKI Motohiro Return-path: Content-Disposition: inline In-Reply-To: <20100415130212.D16E.A69D9226@jp.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Thu, Apr 15, 2010 at 01:09:01PM +0900, KOSAKI Motohiro wrote: > Hi > > > How about this? For now, we stop direct reclaim from doing writeback > > only on order zero allocations, but allow it for higher order > > allocations. That will prevent the majority of situations where > > direct reclaim blows the stack and interferes with background > > writeout, but won't cause lumpy reclaim to change behaviour. > > This reduces the scope of impact and hence testing and validation > > the needs to be done. > > Tend to agree. but I would proposed slightly different algorithm for > avoind incorrect oom. > > for high order allocation > allow to use lumpy reclaim and pageout() for both kswapd and direct reclaim SO same as current. > for low order allocation > - kswapd: always delegate io to flusher thread > - direct reclaim: delegate io to flusher thread only if vm pressure is low IMO, this really doesn't fix either of the problems - the bad IO patterns nor the stack usage. All it will take is a bit more memory pressure to trigger stack and IO problems, and the user reporting the problems is generating an awful lot of memory pressure... Cheers, Dave. -- Dave Chinner david@fromorbit.com