From 1883e8ac96ddd73a87db7f2f8c06111148a3db6f Mon Sep 17 00:00:00 2001
From: Baolin Wang <baolin.wang@linux.alibaba.com>
Date: Mon, 22 Jan 2024 21:01:53 +0800
Subject: [PATCH] mm: compaction: limit the suitable target page order to be
less than cc->order
It can not improve the fragmentation if we isolate the target free pages
exceeding cc->order, especially when the cc->order is less than
pageblock_order. For example, suppose the pageblock_order is MAX_ORDER
(size is 4M) and cc->order is 2M THP size, we should not isolate other 2M
free pages to be the migration target, which can not improve the
fragmentation.
Moreover this is also applicable for large folio compaction.
Link: https://lkml.kernel.org/r/afcd9377351c259df7a25a388a4a0d5862b986f4.1705928395.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/compaction.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 12709d0bcf402..f146478b01bc7 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1365,12 +1365,14 @@ static bool suitable_migration_target(struct compact_control *cc,
{
/* If the page is a large free page, then disallow migration */
if (PageBuddy(page)) {
+ int order = cc->order > 0 ? cc->order : pageblock_order;
+
/*
* We are checking page_order without zone->lock taken. But
* the only small danger is that we skip a potentially suitable
* pageblock, so it's not worth to check order for valid range.
*/
- if (buddy_order_unsafe(page) >= pageblock_order)
+ if (buddy_order_unsafe(page) >= order)
return false;
}
--
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