linux-kernel - [RFC PATCH 2/3] mm, compaction: use MIN_COMPACT_COSTLY

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Date:   Wed, 24 Jul 2019 10:50:13 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Hillf Danton <hdanton@...a.com>, Michal Hocko <mhocko@...nel.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: [RFC PATCH 2/3] mm, compaction: use MIN_COMPACT_COSTLY_PRIORITY everywhere for costly orders

For PAGE_ALLOC_COSTLY_ORDER allocations, MIN_COMPACT_COSTLY_PRIORITY is
minimum (highest priority).  Other places in the compaction code key off
of MIN_COMPACT_PRIORITY.  Costly order allocations will never get to
MIN_COMPACT_PRIORITY.  Therefore, some conditions will never be met for
costly order allocations.

This was observed when hugetlb allocations could stall for minutes or
hours when should_compact_retry() would return true more often then it
should.  Specifically, this was in the case where compact_result was
COMPACT_DEFERRED and COMPACT_PARTIAL_SKIPPED and no progress was being
made.

Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
---
 mm/compaction.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 952dc2fb24e5..325b746068d1 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2294,9 +2294,15 @@ static enum compact_result compact_zone_order(struct zone *zone, int order,
 		.alloc_flags = alloc_flags,
 		.classzone_idx = classzone_idx,
 		.direct_compaction = true,
-		.whole_zone = (prio == MIN_COMPACT_PRIORITY),
-		.ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY),
-		.ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY)
+		.whole_zone = ((order > PAGE_ALLOC_COSTLY_ORDER) ?
+				(prio == MIN_COMPACT_COSTLY_PRIORITY) :
+				(prio == MIN_COMPACT_PRIORITY)),
+		.ignore_skip_hint = ((order > PAGE_ALLOC_COSTLY_ORDER) ?
+				(prio == MIN_COMPACT_COSTLY_PRIORITY) :
+				(prio == MIN_COMPACT_PRIORITY)),
+		.ignore_block_suitable = ((order > PAGE_ALLOC_COSTLY_ORDER) ?
+				(prio == MIN_COMPACT_COSTLY_PRIORITY) :
+				(prio == MIN_COMPACT_PRIORITY))
 	};
 	struct capture_control capc = {
 		.cc = &cc,
@@ -2338,6 +2344,7 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
 	int may_perform_io = gfp_mask & __GFP_IO;
 	struct zoneref *z;
 	struct zone *zone;
+	int min_priority;
 	enum compact_result rc = COMPACT_SKIPPED;
 
 	/*
@@ -2350,12 +2357,13 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
 	trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio);
 
 	/* Compact each zone in the list */
+	min_priority = (order > PAGE_ALLOC_COSTLY_ORDER) ?
+			MIN_COMPACT_COSTLY_PRIORITY : MIN_COMPACT_PRIORITY;
 	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
 								ac->nodemask) {
 		enum compact_result status;
 
-		if (prio > MIN_COMPACT_PRIORITY
-					&& compaction_deferred(zone, order)) {
+		if (prio > min_priority && compaction_deferred(zone, order)) {
 			rc = max_t(enum compact_result, COMPACT_DEFERRED, rc);
 			continue;
 		}
-- 
2.20.1