[RFC PATCH 4/8] mm, compaction: skip on isolation failure also in sync compaction

[Vlastimil Babka <vbabka@suse.cz>]

When scanning for async direct compaction for movable allocation, migration
scanner skips all pages of an order-aligned block once a page fails isolation,
because a single page is enough to prevent forming a free page of given order.
The same is true for sync compaction, so extend the heuristic to there as well.

But make sure we don't skip inside !MOVABLE pageblocks, where we generally want
to migrate all movable pages away from them to prevent non-movable allocations
falling back to more movable blocks before using up all non-movable blocks for
non-movable allocations. Until now this goal relied on async direct compaction
for movable allocation scanning only movable pageblocks, and sync direct
compaction to not skip at all.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/compaction.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 00dc46343093..4f93a7307fb5 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -703,6 +703,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 	unsigned long start_pfn = low_pfn;
 	bool skip_on_failure = false, skipped_pages = false;
 	unsigned long next_skip_pfn = 0;
+	int pageblock_mt;
 
 	/*
 	 * Ensure that there are not too many pages isolated from the LRU
@@ -723,10 +724,13 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 	if (compact_should_abort(cc))
 		return 0;
 
-	if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC) &&
-			cc->migratetype == MIGRATE_MOVABLE) {
-		skip_on_failure = true;
-		next_skip_pfn = block_end_pfn(low_pfn, cc->order);
+	if (cc->direct_compaction && !cc->finishing_block) {
+		pageblock_mt = get_pageblock_migratetype(valid_page);
+		if (pageblock_mt == MIGRATE_MOVABLE
+		    && cc->migratetype == MIGRATE_MOVABLE) {
+			skip_on_failure = true;
+			next_skip_pfn = block_end_pfn(low_pfn, cc->order);
+		}
 	}
 
 	/* Time to isolate some pages for migration */
-- 
2.15.1

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