From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 20 Aug 2007 16:19:47 -0700 (PDT) From: Christoph Lameter Subject: Re: [RFC 7/7] Switch of PF_MEMALLOC during writeout In-Reply-To: Message-ID: References: <20070820215040.937296148@sgi.com> <20070820215317.441134723@sgi.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org Return-Path: To: Andi Kleen Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Mon, 21 Aug 2007, Andi Kleen wrote: > Christoph Lameter writes: > > > Switch off PF_MEMALLOC during both direct and kswapd reclaim. > > > > This works because we are not holding any locks at that point because > > reclaim is essentially complete. The write occurs when the memory on > > the zones is at the high water mark so it is unlikely that writeout > > will get into trouble. If so then reclaim can be called recursively to > > reclaim more pages. > > What would stop multiple recursions in extreme low memory cases? Seems > risky to me and risking stack overflow. Perhaps define another flag to catch that? Right. I am not sure exactly how to handle that. There is also the issue of the writes being deferred. I thought maybe of using pdflush to writeout the pages? Maybe increase priority of the pdflush so that it runs immediately when notified. Shrink_page_list would gather the dirty pages in pvecs and then forward to a pdflush. That may make the whole thing much cleaner. Opinions? -- 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