Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759640Ab1FXOqC (ORCPT ); Fri, 24 Jun 2011 10:46:02 -0400 Received: from cantor2.suse.de ([195.135.220.15]:39008 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759395Ab1FXOpC (ORCPT ); Fri, 24 Jun 2011 10:45:02 -0400 From: Mel Gorman To: Andrew Morton Cc: =?UTF-8?q?P=C3=A1draig=20Brady?= , James Bottomley , Colin King , Minchan Kim , Andrew Lutomirski , Rik van Riel , Johannes Weiner , linux-mm , linux-kernel , Mel Gorman Subject: [PATCH 2/4] mm: vmscan: Do not apply pressure to slab if we are not applying pressure to zone Date: Fri, 24 Jun 2011 15:44:55 +0100 Message-Id: <1308926697-22475-3-git-send-email-mgorman@suse.de> X-Mailer: git-send-email 1.7.3.4 In-Reply-To: <1308926697-22475-1-git-send-email-mgorman@suse.de> References: <1308926697-22475-1-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2677 Lines: 74 During allocator-intensive workloads, kswapd will be woken frequently causing free memory to oscillate between the high and min watermark. This is expected behaviour. When kswapd applies pressure to zones during node balancing, it checks if the zone is above a high+balance_gap threshold. If it is, it does not apply pressure but it unconditionally shrinks slab on a global basis which is excessive. In the event kswapd is being kept awake due to a high small unreclaimable zone, it skips zone shrinking but still calls shrink_slab(). Once pressure has been applied, the check for zone being unreclaimable is being made before the check is made if all_unreclaimable should be set. This miss of unreclaimable can cause has_under_min_watermark_zone to be set due to an unreclaimable zone preventing kswapd backing off on congestion_wait(). Reported-and-tested-by: Pádraig Brady Signed-off-by: Mel Gorman --- mm/vmscan.c | 23 +++++++++++++---------- 1 files changed, 13 insertions(+), 10 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 841e3bf..9cebed1 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2507,18 +2507,18 @@ loop_again: KSWAPD_ZONE_BALANCE_GAP_RATIO); if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) + balance_gap, - end_zone, 0)) + end_zone, 0)) { shrink_zone(priority, zone, &sc); - reclaim_state->reclaimed_slab = 0; - nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages); - sc.nr_reclaimed += reclaim_state->reclaimed_slab; - total_scanned += sc.nr_scanned; - if (zone->all_unreclaimable) - continue; - if (nr_slab == 0 && - !zone_reclaimable(zone)) - zone->all_unreclaimable = 1; + reclaim_state->reclaimed_slab = 0; + nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages); + sc.nr_reclaimed += reclaim_state->reclaimed_slab; + total_scanned += sc.nr_scanned; + + if (nr_slab == 0 && !zone_reclaimable(zone)) + zone->all_unreclaimable = 1; + } + /* * If we've done a decent amount of scanning and * the reclaim ratio is low, start doing writepage @@ -2528,6 +2528,9 @@ loop_again: total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) sc.may_writepage = 1; + if (zone->all_unreclaimable) + continue; + if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), end_zone, 0)) { all_zones_ok = 0; -- 1.7.3.4 -- 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/