linux-kernel - [PATCH] mm: page_alloc: use the correct THP order for THP PCP

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Date: Wed,  3 Apr 2024 21:47:21 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: akpm@...ux-foundation.org
Cc: mgorman@...hsingularity.net,
	vbabka@...e.cz,
	baolin.wang@...ux.alibaba.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] mm: page_alloc: use the correct THP order for THP PCP

Commit 44042b449872 ("mm/page_alloc: allow high-order pages to be stored
on the per-cpu lists") extends the PCP allocator to store THP pages, and
it determines whether to cache THP pags in PCP by comparing with pageblock_order.
But the pageblock_order is not always equal to THP order, it might also
be MAX_PAGE_ORDER, which could prevent PCP from caching THP pages.

Therefore, using HPAGE_PMD_ORDER instead to determine the need for caching
THP for PCP can fix this issue

Fixes: 44042b449872 ("mm/page_alloc: allow high-order pages to be stored on the per-cpu lists")
Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
 mm/page_alloc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 1beb56f75319..915f4ef070da 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -506,7 +506,7 @@ static inline unsigned int order_to_pindex(int migratetype, int order)
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	if (order > PAGE_ALLOC_COSTLY_ORDER) {
-		VM_BUG_ON(order != pageblock_order);
+		VM_BUG_ON(order != HPAGE_PMD_ORDER);
 		return NR_LOWORDER_PCP_LISTS;
 	}
 #else
@@ -522,7 +522,7 @@ static inline int pindex_to_order(unsigned int pindex)
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	if (pindex == NR_LOWORDER_PCP_LISTS)
-		order = pageblock_order;
+		order = HPAGE_PMD_ORDER;
 #else
 	VM_BUG_ON(order > PAGE_ALLOC_COSTLY_ORDER);
 #endif
@@ -535,7 +535,7 @@ static inline bool pcp_allowed_order(unsigned int order)
 	if (order <= PAGE_ALLOC_COSTLY_ORDER)
 		return true;
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-	if (order == pageblock_order)
+	if (order == HPAGE_PMD_ORDER)
 		return true;
 #endif
 	return false;
-- 
2.39.3