Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754396Ab0K3JSk (ORCPT ); Tue, 30 Nov 2010 04:18:40 -0500 Received: from gir.skynet.ie ([193.1.99.77]:58333 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751043Ab0K3JSi (ORCPT ); Tue, 30 Nov 2010 04:18:38 -0500 Date: Tue, 30 Nov 2010 09:18:22 +0000 From: Mel Gorman To: KOSAKI Motohiro Cc: Minchan Kim , Andrew Morton , linux-mm , LKML , Ben Gamari , Wu Fengguang , Johannes Weiner , Nick Piggin Subject: Re: [PATCH 2/3] Reclaim invalidated page ASAP Message-ID: <20101130091822.GJ13268@csn.ul.ie> References: <053e6a3308160a8992af5a47fb4163796d033b08.1291043274.git.minchan.kim@gmail.com> <20101130100933.82E9.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20101130100933.82E9.A69D9226@jp.fujitsu.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2399 Lines: 56 On Tue, Nov 30, 2010 at 10:10:20AM +0900, KOSAKI Motohiro wrote: > > invalidate_mapping_pages is very big hint to reclaimer. > > It means user doesn't want to use the page any more. > > So in order to prevent working set page eviction, this patch > > move the page into tail of inactive list by PG_reclaim. > > > > Please, remember that pages in inactive list are working set > > as well as active list. If we don't move pages into inactive list's > > tail, pages near by tail of inactive list can be evicted although > > we have a big clue about useless pages. It's totally bad. > > > > Now PG_readahead/PG_reclaim is shared. > > fe3cba17 added ClearPageReclaim into clear_page_dirty_for_io for > > preventing fast reclaiming readahead marker page. > > > > In this series, PG_reclaim is used by invalidated page, too. > > If VM find the page is invalidated and it's dirty, it sets PG_reclaim > > to reclaim asap. Then, when the dirty page will be writeback, > > clear_page_dirty_for_io will clear PG_reclaim unconditionally. > > It disturbs this serie's goal. > > > > I think it's okay to clear PG_readahead when the page is dirty, not > > writeback time. So this patch moves ClearPageReadahead. > > > > Signed-off-by: Minchan Kim > > Acked-by: Rik van Riel > > Cc: Wu Fengguang > > Cc: KOSAKI Motohiro > > Cc: Johannes Weiner > > Cc: Nick Piggin > > Cc: Mel Gorman > > I still dislike this one. I doubt this trick makes much benefit in real > world workload. > I would agree except as said elsewhere, it's a chicken and egg problem. We don't have a real world test because fadvise is not useful in its current iteration. I'm hoping that there will be a test comparing rsync on vanilla kernel rsync on patched kernel rsync+patch on vanilla kernel rsync+patch on patched kernel Are the results of such a test likely to happen? -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/