From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id 53C85900234 for ; Fri, 24 Jun 2011 09:43:24 -0400 (EDT) From: 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 14:43:16 +0100 Message-Id: <1308922998-15529-3-git-send-email-mgorman@suse.de> In-Reply-To: <1308922998-15529-1-git-send-email-mgorman@suse.de> References: <1308922998-15529-1-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: 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 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: PA!draig Brady Signed-off-by: Mel Gorman --- mm/vmscan.c | 21 ++++++++++++--------- 1 files changed, 12 insertions(+), 9 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 841e3bf..38665ec 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2509,16 +2509,16 @@ loop_again: high_wmark_pages(zone) + balance_gap, 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, 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org