Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755083Ab3CSKOc (ORCPT ); Tue, 19 Mar 2013 06:14:32 -0400 Received: from cantor2.suse.de ([195.135.220.15]:58760 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754564Ab3CSKOb (ORCPT ); Tue, 19 Mar 2013 06:14:31 -0400 Date: Tue, 19 Mar 2013 10:14:28 +0000 From: Mel Gorman To: Simon Jeons Cc: Linux-MM , Jiri Slaby , Valdis Kletnieks , Rik van Riel , Zlatko Calusic , Johannes Weiner , dormando , Satoru Moriya , Michal Hocko , LKML Subject: Re: [PATCH 03/10] mm: vmscan: Flatten kswapd priority loop Message-ID: <20130319101428.GD2055@suse.de> References: <1363525456-10448-1-git-send-email-mgorman@suse.de> <1363525456-10448-4-git-send-email-mgorman@suse.de> <5147D6A7.5060008@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <5147D6A7.5060008@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2385 Lines: 58 On Tue, Mar 19, 2013 at 11:08:23AM +0800, Simon Jeons wrote: > Hi Mel, > On 03/17/2013 09:04 PM, Mel Gorman wrote: > >kswapd stops raising the scanning priority when at least SWAP_CLUSTER_MAX > >pages have been reclaimed or the pgdat is considered balanced. It then > >rechecks if it needs to restart at DEF_PRIORITY and whether high-order > >reclaim needs to be reset. This is not wrong per-se but it is confusing > > per-se is short for what? > It means "in self" or "as such". > >to follow and forcing kswapd to stay at DEF_PRIORITY may require several > >restarts before it has scanned enough pages to meet the high watermark even > >at 100% efficiency. This patch irons out the logic a bit by controlling > >when priority is raised and removing the "goto loop_again". > > > >This patch has kswapd raise the scanning priority until it is scanningmm: vmscan: Flatten kswapd priority loop > >enough pages that it could meet the high watermark in one shrink of the > >LRU lists if it is able to reclaim at 100% efficiency. It will not raise > > Which kind of reclaim can be treated as 100% efficiency? > 100% efficiency is where every page scanned can be reclaimed immediately. > > /* > >- * We do this so kswapd doesn't build up large priorities for > >- * example when it is freeing in parallel with allocators. It > >- * matches the direct reclaim path behaviour in terms of impact > >- * on zone->*_priority. > >+ * Fragmentation may mean that the system cannot be rebalanced > >+ * for high-order allocations in all zones. If twice the > >+ * allocation size has been reclaimed and the zones are still > >+ * not balanced then recheck the watermarks at order-0 to > >+ * prevent kswapd reclaiming excessively. Assume that a > >+ * process requested a high-order can direct reclaim/compact. > > */ > >- if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) > >- break; > >- } while (--sc.priority >= 0); > >+ if (order && sc.nr_reclaimed >= 2UL << order) > >+ order = sc.order = 0; > > If order == 0 is meet, should we do defrag for it? > Compaction is unnecessary for order-0. -- Mel Gorman SUSE Labs -- 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/