[RFC PATCH 2/4] mm: compaction: skip isolating large folios that satisfy the mTHP order

[Bo Zhang <zhangbo0325@gmail.com>]

When proactive compaction is triggered via compact_memory and mTHP
always-enabled orders are configured, skip isolating folios whose order
is >= the minimum always-enabled mTHP order. These folios already satisfy
mTHP allocation requirements and migrating them is unnecessary overhead.

Signed-off-by: Bo Zhang <zhangbo56@xiaomi.com>
---
 mm/compaction.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/mm/compaction.c b/mm/compaction.c
index a4f87232ad80..a15ed2576562 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -837,6 +837,12 @@ static bool skip_isolation_on_order(int order, int target_order)
 	 */
 	if (!is_via_compact_memory(target_order) && order >= target_order)
 		return true;
+
+	/* We are compacting for multi-size THP allocation */
+	if (is_via_compact_memory(target_order) && order >= compact_hpage_order() &&
+	    READ_ONCE(huge_anon_orders_always))
+		return true;
+
 	/*
 	 * We limit memory compaction to pageblocks and won't try
 	 * creating free blocks of memory that are larger than that.
-- 
2.34.1