From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id 16F4A6B024D for ; Wed, 21 Jul 2010 10:31:37 -0400 (EDT) Date: Wed, 21 Jul 2010 15:31:19 +0100 From: Mel Gorman Subject: Re: [PATCH 4/8] vmscan: Do not writeback filesystem pages in direct reclaim Message-ID: <20100721143118.GA13117@csn.ul.ie> References: <1279545090-19169-1-git-send-email-mel@csn.ul.ie> <1279545090-19169-5-git-send-email-mel@csn.ul.ie> <20100719221420.GA16031@cmpxchg.org> <20100720134555.GU13117@csn.ul.ie> <20100720220218.GE16031@cmpxchg.org> <20100721115250.GX13117@csn.ul.ie> <20100721130435.GH16031@cmpxchg.org> <20100721133857.GY13117@csn.ul.ie> <20100721142819.GA10480@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20100721142819.GA10480@cmpxchg.org> Sender: owner-linux-mm@kvack.org To: Johannes Weiner Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner , Chris Mason , Nick Piggin , Rik van Riel , Christoph Hellwig , Wu Fengguang , KAMEZAWA Hiroyuki , KOSAKI Motohiro , Andrew Morton , Andrea Arcangeli List-ID: On Wed, Jul 21, 2010 at 04:28:44PM +0200, Johannes Weiner wrote: > On Wed, Jul 21, 2010 at 02:38:57PM +0100, Mel Gorman wrote: > > Here is an updated version. Thanks very much > > > > ==== CUT HERE ==== > > vmscan: Do not writeback filesystem pages in direct reclaim > > > > When memory is under enough pressure, a process may enter direct > > reclaim to free pages in the same manner kswapd does. If a dirty page is > > encountered during the scan, this page is written to backing storage using > > mapping->writepage. This can result in very deep call stacks, particularly > > if the target storage or filesystem are complex. It has already been observed > > on XFS that the stack overflows but the problem is not XFS-specific. > > > > This patch prevents direct reclaim writing back filesystem pages by checking > > if current is kswapd or the page is anonymous before writing back. If the > > dirty pages cannot be written back, they are placed back on the LRU lists > > for either background writing by the BDI threads or kswapd. If in direct > > lumpy reclaim and dirty pages are encountered, the process will stall for > > the background flusher before trying to reclaim the pages again. > > > > As the call-chain for writing anonymous pages is not expected to be deep > > and they are not cleaned by flusher threads, anonymous pages are still > > written back in direct reclaim. > > > > Signed-off-by: Mel Gorman > > Acked-by: Rik van Riel > > Cool! > > Except for one last tiny thing... > > > @@ -858,7 +872,7 @@ keep: > > > > free_page_list(&free_pages); > > > > - list_splice(&ret_pages, page_list); > > This will lose all retry pages forever, I think. > Above this is while (!list_empty(page_list)) { ... } page_list should be empty and keep_locked is putting the pages on ret_pages already so I think it's ok. > > + *nr_still_dirty = nr_dirty; > > count_vm_events(PGACTIVATE, pgactivate); > > return nr_reclaimed; > > } > > Otherwise, > Reviewed-by: Johannes Weiner > Thanks! -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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