Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752408Ab3CRLfI (ORCPT ); Mon, 18 Mar 2013 07:35:08 -0400 Received: from mail-oa0-f45.google.com ([209.85.219.45]:34677 "EHLO mail-oa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750899Ab3CRLfF (ORCPT ); Mon, 18 Mar 2013 07:35:05 -0400 MIME-Version: 1.0 In-Reply-To: <1363525456-10448-5-git-send-email-mgorman@suse.de> References: <1363525456-10448-1-git-send-email-mgorman@suse.de> <1363525456-10448-5-git-send-email-mgorman@suse.de> Date: Mon, 18 Mar 2013 19:35:04 +0800 Message-ID: Subject: Re: [PATCH 04/10] mm: vmscan: Decide whether to compact the pgdat based on reclaim progress From: Hillf Danton To: Mel Gorman Cc: Linux-MM , Jiri Slaby , Valdis Kletnieks , Rik van Riel , Zlatko Calusic , Johannes Weiner , dormando , Satoru Moriya , Mi@jasper.es, LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5736 Lines: 129 On Sun, Mar 17, 2013 at 9:04 PM, Mel Gorman wrote: > In the past, kswapd makes a decision on whether to compact memory after the > pgdat was considered balanced. This more or less worked but it is late to > make such a decision and does not fit well now that kswapd makes a decision > whether to exit the zone scanning loop depending on reclaim progress. > > This patch will compact a pgdat if at least the requested number of pages > were reclaimed from unbalanced zones for a given priority. If any zone is > currently balanced, kswapd will not call compaction as it is expected the > necessary pages are already available. > > Signed-off-by: Mel Gorman > --- > mm/vmscan.c | 52 +++++++++++++++++++++------------------------------- > 1 file changed, 21 insertions(+), 31 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 279d0c2..7513bd1 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2694,8 +2694,11 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, > > do { > unsigned long lru_pages = 0; > + unsigned long nr_to_reclaim = 0; > unsigned long nr_reclaimed = sc.nr_reclaimed; > + unsigned long this_reclaimed; > bool raise_priority = true; > + bool pgdat_needs_compaction = true; To show that compaction is needed iff non order-o reclaim, bool do_compaction = !!order; > > /* > * Scan in the highmem->dma direction for the highest > @@ -2743,7 +2746,17 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, > for (i = 0; i <= end_zone; i++) { > struct zone *zone = pgdat->node_zones + i; > > + if (!populated_zone(zone)) > + continue; > + > lru_pages += zone_reclaimable_pages(zone); > + > + /* Check if the memory needs to be defragmented */ Enrich the comment with, say, /*If any zone is currently balanced, kswapd will not call compaction as it is expected the necessary pages are already available.*/ please since a big one is deleted below. > + if (order && pgdat_needs_compaction && > + zone_watermark_ok(zone, order, > + low_wmark_pages(zone), > + *classzone_idx, 0)) > + pgdat_needs_compaction = false; > } > > /* > @@ -2814,6 +2827,8 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, > */ > if (kswapd_shrink_zone(zone, &sc, lru_pages)) > raise_priority = false; > + > + nr_to_reclaim += sc.nr_to_reclaim; > } > > /* > @@ -2864,46 +2879,21 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, > if (try_to_freeze() || kthread_should_stop()) > break; > > - /* If no reclaim progress then increase scanning priority */ > - if (sc.nr_reclaimed - nr_reclaimed == 0) > - raise_priority = true; > + /* Compact if necessary and kswapd is reclaiming efficiently */ > + this_reclaimed = sc.nr_reclaimed - nr_reclaimed; > + if (order && pgdat_needs_compaction && > + this_reclaimed > nr_to_reclaim) > + compact_pgdat(pgdat, order); > > /* > * Raise priority if scanning rate is too low or there was no > * progress in reclaiming pages > */ > - if (raise_priority || sc.nr_reclaimed - nr_reclaimed == 0) > + if (raise_priority || !this_reclaimed) > sc.priority--; > } while (sc.priority >= 0 && > !pgdat_balanced(pgdat, order, *classzone_idx)); > > - /* > - * If kswapd was reclaiming at a higher order, it has the option of > - * sleeping without all zones being balanced. Before it does, it must > - * ensure that the watermarks for order-0 on *all* zones are met and > - * that the congestion flags are cleared. The congestion flag must > - * be cleared as kswapd is the only mechanism that clears the flag > - * and it is potentially going to sleep here. > - */ > - if (order) { > - int zones_need_compaction = 1; > - > - for (i = 0; i <= end_zone; i++) { > - struct zone *zone = pgdat->node_zones + i; > - > - if (!populated_zone(zone)) > - continue; > - > - /* Check if the memory needs to be defragmented. */ > - if (zone_watermark_ok(zone, order, > - low_wmark_pages(zone), *classzone_idx, 0)) > - zones_need_compaction = 0; > - } > - > - if (zones_need_compaction) > - compact_pgdat(pgdat, order); > - } > - > out: > /* > * Return the order we were reclaiming at so prepare_kswapd_sleep() > -- > 1.8.1.4 -- 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/