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From:   Zi Yan <zi.yan@sent.com>
To:     linux-mm@kvack.org, linux-kernel@vger.kernel.org
Cc:     Zi Yan <ziy@nvidia.com>, Ryan Roberts <ryan.roberts@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        David Hildenbrand <david@redhat.com>,
        "Yin, Fengwei" <fengwei.yin@intel.com>,
        Yu Zhao <yuzhao@google.com>, Vlastimil Babka <vbabka@suse.cz>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Baolin Wang <baolin.wang@linux.alibaba.com>,
        Kemeng Shi <shikemeng@huaweicloud.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Rohan Puri <rohan.puri15@gmail.com>,
        Mcgrof Chamberlain <mcgrof@kernel.org>,
        Adam Manzanares <a.manzanares@samsung.com>,
        John Hubbard <jhubbard@nvidia.com>
Subject: [RFC PATCH 3/4] mm/compaction: optimize >0 order folio compaction by sorting source pages.
Date:   Tue, 12 Sep 2023 12:28:14 -0400
Message-Id: <20230912162815.440749-4-zi.yan@sent.com>
In-Reply-To: <20230912162815.440749-1-zi.yan@sent.com>
References: <20230912162815.440749-1-zi.yan@sent.com>
Reply-To: Zi Yan <ziy@nvidia.com>
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From: Zi Yan <ziy@nvidia.com>

It should maximize high order free page use and minimize free page splits.
It might be useful before free page merging is implemented.

Signed-off-by: Zi Yan <ziy@nvidia.com>
---
 mm/compaction.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/mm/compaction.c b/mm/compaction.c
index 45747ab5f380..4300d877b824 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -145,6 +145,38 @@ static void sort_free_pages(struct list_head *src, str=
uct free_list *dst)
 	}
 }
=20
+static void sort_folios_by_order(struct list_head *pages)
+{
+	struct free_list page_list[MAX_ORDER + 1];
+	int order;
+	struct folio *folio, *next;
+
+	for (order =3D 0; order <=3D MAX_ORDER; order++) {
+		INIT_LIST_HEAD(&page_list[order].pages);
+		page_list[order].nr_free =3D 0;
+	}
+
+	list_for_each_entry_safe(folio, next, pages, lru) {
+		order =3D folio_order(folio);
+
+		if (order > MAX_ORDER)
+			continue;
+
+		list_move(&folio->lru, &page_list[order].pages);
+		page_list[order].nr_free++;
+	}
+
+	for (order =3D MAX_ORDER; order >=3D 0; order--) {
+		if (page_list[order].nr_free) {
+
+			list_for_each_entry_safe(folio, next,
+						 &page_list[order].pages, lru) {
+				list_move_tail(&folio->lru, pages);
+			}
+		}
+	}
+}
+
 #ifdef CONFIG_COMPACTION
 bool PageMovable(struct page *page)
 {
@@ -2636,6 +2668,8 @@ compact_zone(struct compact_control *cc, struct captu=
re_control *capc)
 				pageblock_start_pfn(cc->migrate_pfn - 1));
 		}
=20
+		sort_folios_by_order(&cc->migratepages);
+
 		err =3D migrate_pages(&cc->migratepages, compaction_alloc,
 				compaction_free, (unsigned long)cc, cc->mode,
 				MR_COMPACTION, &nr_succeeded);
--=20
2.40.1