linux-kernel - [PATCH linux-next] mm/page_alloc: avoid overcounting bulk alloc in watermark check

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Message-ID: <tencent_F36C5B5FB4DED98C79D9BDEE1210CD338C06@qq.com>
Date: Thu, 29 Jan 2026 22:38:14 +0800
From: "shengminghu512" <shengminghu512@...com>
To: "akpm" <akpm@...ux-foundation.org>, "vbabka" <vbabka@...e.cz>, "surenb" <surenb@...gle.com>, "mhocko" <mhocko@...e.com>, "jackmanb" <jackmanb@...gle.com>, "hannes" <hannes@...xchg.org>
Cc: "ziy" <ziy@...dia.com>, "inux-mm" <inux-mm@...ck.org>, "linux-kernel" <linux-kernel@...r.kernel.org>, "hu.shengming" <hu.shengming@....com.cn>, "zhang.run" <zhang.run@....com.cn>
Subject: [PATCH linux-next] mm/page_alloc: avoid overcounting bulk alloc in watermark check

From: Shengming Hu <hu.shengming@....com.cn>

alloc_pages_bulk_noprof() only fills NULL slots and already tracks how many
entries are pre-populated via nr_populated.

The fast watermark check was adding nr_pages unconditionally, which can
overestimate the demand. Use (nr_pages - nr_populated) instead, as an 
upper bound on the remaining pages this call can still allocate without
scanning the whole array.

Signed-off-by: Shengming Hu <hu.shengming@....com.cn>
---
 mm/page_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5fd9e4a03..90b978802 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5130,7 +5130,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid,
 
 		cond_accept_memory(zone, 0, alloc_flags);
 retry_this_zone:
-		mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages;
+		mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages - nr_populated;
 		if (zone_watermark_fast(zone, 0,  mark,
 				zonelist_zone_idx(ac.preferred_zoneref),
 				alloc_flags, gfp)) {
-- 
2.25.1