The patch titled
Subject: mm/list_lru: make the case where mlru is NULL as unlikely
has been added to the -mm mm-unstable branch. Its filename is
mm-list_lru-make-the-case-where-mlru-is-null-as-unlikely.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-list_lru-make-the-case-where-mlru-is-null-as-unlikely.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Zeng Jingxiang <linuszeng@xxxxxxxxxxx>
Subject: mm/list_lru: make the case where mlru is NULL as unlikely
Date: Thu, 27 Feb 2025 16:22:23 +0800
In the following memcg_list_lru_alloc() function, mlru here is almost
always NULL, so in most cases this should save a function call, mark mlru
as unlikely to optimize the code, and reusing the mlru for the next
attempt when the tree insertion fails.
do {
xas_lock_irqsave(&xas, flags);
if (!xas_load(&xas) && !css_is_dying(&pos->css)) {
xas_store(&xas, mlru);
if (!xas_error(&xas))
mlru = NULL;
}
xas_unlock_irqrestore(&xas, flags);
} while (xas_nomem(&xas, GFP_KERNEL));
> if (mlru)
kfree(mlru);
Link: https://lkml.kernel.org/r/20250227082223.1173847-1-jingxiangzeng.cas@xxxxxxxxx
Signed-off-by: Zeng Jingxiang <linuszeng@xxxxxxxxxxx>
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-kbuild-all/202412290924.UTP7GH2Z-lkp@xxxxxxxxx/
Suggested-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Muchun Song <muchun.song@xxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Cc: Chengming Zhou <chengming.zhou@xxxxxxxxx>
Cc: Jingxiang Zeng <linuszeng@xxxxxxxxxxx>
Cc: Kairui Song <kasong@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/list_lru.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
--- a/mm/list_lru.c~mm-list_lru-make-the-case-where-mlru-is-null-as-unlikely
+++ a/mm/list_lru.c
@@ -510,7 +510,7 @@ int memcg_list_lru_alloc(struct mem_cgro
gfp_t gfp)
{
unsigned long flags;
- struct list_lru_memcg *mlru;
+ struct list_lru_memcg *mlru = NULL;
struct mem_cgroup *pos, *parent;
XA_STATE(xas, &lru->xa, 0);
@@ -535,9 +535,11 @@ int memcg_list_lru_alloc(struct mem_cgro
parent = parent_mem_cgroup(pos);
}
- mlru = memcg_init_list_lru_one(lru, gfp);
- if (!mlru)
- return -ENOMEM;
+ if (!mlru) {
+ mlru = memcg_init_list_lru_one(lru, gfp);
+ if (!mlru)
+ return -ENOMEM;
+ }
xas_set(&xas, pos->kmemcg_id);
do {
xas_lock_irqsave(&xas, flags);
@@ -548,10 +550,11 @@ int memcg_list_lru_alloc(struct mem_cgro
}
xas_unlock_irqrestore(&xas, flags);
} while (xas_nomem(&xas, gfp));
- if (mlru)
- kfree(mlru);
} while (pos != memcg && !css_is_dying(&pos->css));
+ if (unlikely(mlru))
+ kfree(mlru);
+
return xas_error(&xas);
}
#else
_
Patches currently in -mm which might be from linuszeng@xxxxxxxxxxx are
mm-list_lru-make-the-case-where-mlru-is-null-as-unlikely.patch
