[PATCH v1 4/4] mm/compaction: optimize >0 order folio compaction by sorting source pages.

Zi Yan
2023-11-13T17:02:29Z

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 | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)

diff --git a/mm/compaction.c b/mm/compaction.c
index 9c083e6b399a..91809bee5422 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -127,6 +127,37 @@ static unsigned long release_free_list(struct page_list *freepages)
}

#ifdef CONFIG_COMPACTION
+
+static void sort_folios_by_order(struct list_head *pages)
+{
+ struct page_list page_list[MAX_ORDER + 1];
+ int order;
+ struct folio *folio, *next;
+
+ for (order = 0; order <= MAX_ORDER; order++)
+ init_page_list(&page_list[order]);
+
+ list_for_each_entry_safe(folio, next, pages, lru) {
+ order = folio_order(folio);
+
+ if (order > MAX_ORDER)
+ continue;
+
+ list_move(&folio->lru, &page_list[order].pages);
+ page_list[order].nr_pages++;
+ }
+
+ for (order = MAX_ORDER; order >= 0; order--) {
+ if (page_list[order].nr_pages) {
+
+ list_for_each_entry_safe(folio, next,
+ &page_list[order].pages, lru) {
+ list_move_tail(&folio->lru, pages);
+ }
+ }
+ }
+}
+
bool PageMovable(struct page *page)
{
const struct movable_operations *mops;
@@ -2639,6 +2670,8 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
pageblock_start_pfn(cc->migrate_pfn - 1));
}

+ sort_folios_by_order(&cc->migratepages);
+
err = migrate_pages(&cc->migratepages, compaction_alloc,
compaction_free, (unsigned long)cc, cc->mode,
MR_COMPACTION, &nr_succeeded);
--
2.42.0