linux-kernel - [PATCH] mm: Inline vma_needs

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Message-ID: <20250618014209.1195734-1-jiangyunshui@kylinos.cn>
Date: Wed, 18 Jun 2025 09:42:09 +0800
From: Yunshui Jiang <jiangyunshui@...inos.cn>
To: linux-kernel@...r.kernel.org,
	linux-mm@...k.org
Cc: akpm@...ux-foundation.org,
	david@...hat.com,
	lorenzo.stoakes@...cle.com,
	Liam.Howlett@...cle.com,
	vbabka@...e.cz,
	jiangyunshui <jiangyunshui@...inos.cn>
Subject: [PATCH] mm: Inline vma_needs_copy

From: jiangyunshui <jiangyunshui@...inos.cn>

Since commit bcd51a3c679d ("hugetlb: lazy page table copies
in fork()"), the logic about judging whether to copy
page table inside func copy_page_range has been extracted
into a separate func vma_needs_copy. While this change
improves code readability, it also incurs more function call
overhead, especially where fork() were frequently called.

Inline func vma_needs_copy to optimize the copy_page_range
performance. Given that func vma_needs_copy is only called
by copy_page_range, inlining it would not cause unacceptable
code bloat.

Testing was done with the byte-unixbench spawn benchmark
(which frequently calls fork). I measured 1.7% improvement
on x86 and 1.8% improvement on arm64.

Signed-off-by: jiangyunshui <jiangyunshui@...inos.cn>
---
 mm/memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index 8eba595056fe..d15b07f96ab1 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1337,7 +1337,7 @@ copy_p4d_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
  * false when we can speed up fork() by allowing lazy page faults later until
  * when the child accesses the memory range.
  */
-static bool
+static __always_inline bool
 vma_needs_copy(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
 {
 	/*
-- 
2.47.1