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

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Message-Id: <20230912162815.440749-5-zi.yan@sent.com>
Date:   Tue, 12 Sep 2023 12:28:15 -0400
From:   Zi Yan <zi.yan@...t.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     Zi Yan <ziy@...dia.com>, Ryan Roberts <ryan.roberts@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        "Yin, Fengwei" <fengwei.yin@...el.com>,
        Yu Zhao <yuzhao@...gle.com>, Vlastimil Babka <vbabka@...e.cz>,
        Johannes Weiner <hannes@...xchg.org>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Kemeng Shi <shikemeng@...weicloud.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Rohan Puri <rohan.puri15@...il.com>,
        Mcgrof Chamberlain <mcgrof@...nel.org>,
        Adam Manzanares <a.manzanares@...sung.com>,
        John Hubbard <jhubbard@...dia.com>
Subject: [RFC PATCH 4/4] mm/compaction: enable compacting >0 order folios.

From: Zi Yan <ziy@...dia.com>

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

Signed-off-by: Zi Yan <ziy@...dia.com>
---
 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