[RFC PATCH 4/4] mm/compaction: enable compacting >0 order folios.

[Zi Yan]

From: Zi Yan <ziy@xxxxxxxxxx>

Since compaction code can compact >0 order folios, enable it during the
process.

Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
---
 mm/compaction.c | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 4300d877b824..f72af74094de 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1087,11 +1087,17 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 		if (PageCompound(page) && !cc->alloc_contig) {
 			const unsigned int order = compound_order(page);
 
-			if (likely(order <= MAX_ORDER)) {
-				low_pfn += (1UL << order) - 1;
-				nr_scanned += (1UL << order) - 1;
+			/*
+			 * Compacting > pageblock_order pages does not improve
+			 * memory fragmentation. Also skip hugetlbfs pages.
+			 */
+			if (likely(order >= pageblock_order) || PageHuge(page)) {
+				if (order <= MAX_ORDER) {
+					low_pfn += (1UL << order) - 1;
+					nr_scanned += (1UL << order) - 1;
+				}
+				goto isolate_fail;
 			}
-			goto isolate_fail;
 		}
 
 		/*
@@ -1214,17 +1220,6 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
 					goto isolate_abort;
 				}
 			}
-
-			/*
-			 * folio become large since the non-locked check,
-			 * and it's on LRU.
-			 */
-			if (unlikely(folio_test_large(folio) && !cc->alloc_contig)) {
-				low_pfn += folio_nr_pages(folio) - 1;
-				nr_scanned += folio_nr_pages(folio) - 1;
-				folio_set_lru(folio);
-				goto isolate_fail_put;
-			}
 		}
 
 		/* The folio is taken off the LRU */
-- 
2.40.1