+ ksm-initialize-the-addr-only-once-in-rmap_walk_ksm.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: ksm: initialize the addr only once in rmap_walk_ksm
has been added to the -mm mm-new branch.  Its filename is
     ksm-initialize-the-addr-only-once-in-rmap_walk_ksm.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ksm-initialize-the-addr-only-once-in-rmap_walk_ksm.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

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------------------------------------------------------
From: xu xin <xu.xin16@zte.com.cn>
Subject: ksm: initialize the addr only once in rmap_walk_ksm
Date: Thu, 12 Feb 2026 19:29:32 +0800 (CST)

Patch series "KSM: Optimizations for rmap_walk_ksm", v3.

There are two performance optimization patches for rmap_walk_ksm.

The patch [1/2] move the initializaion of addr from the position inside
loop to the position before the loop, since the variable will not change
in the loop.

The patch [2/2] optimize rmap_walk_ksm by passing a suitable page offset
range to the anon_vma_interval_tree_foreach loop to reduce ineffective
checks.

The metric performance and reproducer can be found at patch[2/2].


This patch (of 2):

This is a minor performance optimization, especially when there are many
for-loop iterations, because the addr variable doesn't change across
iterations.

Therefore, it only needs to be initialized once before the loop.

Link: https://lkml.kernel.org/r/20260212192820223O_r2NQzSEPG_C56cs-z4l@zte.com.cn
Link: https://lkml.kernel.org/r/20260212192932941MSsJEAyoRW4YdLBN7_myn@zte.com.cn
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Hugh Dickins <hughd@google.com>
Cc: Wang Yaxin <wang.yaxin@zte.com.cn>
Cc: Yang Yang <yang.yang29@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/ksm.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--- a/mm/ksm.c~ksm-initialize-the-addr-only-once-in-rmap_walk_ksm
+++ a/mm/ksm.c
@@ -3168,6 +3168,8 @@ void rmap_walk_ksm(struct folio *folio,
 		return;
 again:
 	hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) {
+		/* Ignore the stable/unstable/sqnr flags */
+		const unsigned long addr = rmap_item->address & PAGE_MASK;
 		struct anon_vma *anon_vma = rmap_item->anon_vma;
 		struct anon_vma_chain *vmac;
 		struct vm_area_struct *vma;
@@ -3180,16 +3182,13 @@ again:
 			}
 			anon_vma_lock_read(anon_vma);
 		}
+
 		anon_vma_interval_tree_foreach(vmac, &anon_vma->rb_root,
 					       0, ULONG_MAX) {
-			unsigned long addr;
 
 			cond_resched();
 			vma = vmac->vma;
 
-			/* Ignore the stable/unstable/sqnr flags */
-			addr = rmap_item->address & PAGE_MASK;
-
 			if (addr < vma->vm_start || addr >= vma->vm_end)
 				continue;
 			/*
_

Patches currently in -mm which might be from xu.xin16@zte.com.cn are

ksm-initialize-the-addr-only-once-in-rmap_walk_ksm.patch
ksm-optimize-rmap_walk_ksm-by-passing-a-suitable-address-range.patch