From c702418f8a2fa6cc92e84a39880d458faf7af9cc Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Tue, 4 Dec 2012 11:11:31 -0500 Subject: [PATCH] mm: vmscan: do not keep kswapd looping forever due to individual uncompactable zones When a zone meets its high watermark and is compactable in case of higher order allocations, it contributes to the percentage of the node's memory that is considered balanced. This requirement, that a node be only partially balanced, came about when kswapd was desparately trying to balance tiny zones when all bigger zones in the node had plenty of free memory. Arguably, the same should apply to compaction: if a significant part of the node is balanced enough to run compaction, do not get hung up on that tiny zone that might never get in shape. When the compaction logic in kswapd is reached, we know that at least 25% of the node's memory is balanced properly for compaction (see zone_balanced and pgdat_balanced). Remove the individual zone checks that restart the kswapd cycle. Otherwise, we may observe more endless looping in kswapd where the compaction code loops back to reclaim because of a single zone and reclaim does nothing because the node is considered balanced overall. See for example https://bugzilla.redhat.com/show_bug.cgi?id=866988 Signed-off-by: Johannes Weiner Reported-and-tested-by: Thorsten Leemhuis Reported-by: Jiri Slaby Tested-by: John Ellson Tested-by: Zdenek Kabelac Tested-by: Bruno Wolff III Signed-off-by: Linus Torvalds --- mm/vmscan.c | 16 ---------------- 1 file changed, 16 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 83f4d0e85601..124bbfe5cc52 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2823,22 +2823,6 @@ out: if (!populated_zone(zone)) continue; - if (zone->all_unreclaimable && - sc.priority != DEF_PRIORITY) - continue; - - /* Would compaction fail due to lack of free memory? */ - if (COMPACTION_BUILD && - compaction_suitable(zone, order) == COMPACT_SKIPPED) - goto loop_again; - - /* Confirm the zone is balanced for order-0 */ - if (!zone_watermark_ok(zone, 0, - high_wmark_pages(zone), 0, 0)) { - order = sc.order = 0; - goto loop_again; - } - /* Check if the memory needs to be defragmented. */ if (zone_watermark_ok(zone, order, low_wmark_pages(zone), *classzone_idx, 0)) -- 2.20.1