Commit b9585a3f authored by Zeng Jingxiang's avatar Zeng Jingxiang Committed by Andrew Morton
Browse files

mm/list_lru: make the case where mlru is NULL as unlikely 

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@gmail.com


Signed-off-by: default avatarZeng Jingxiang <linuszeng@tencent.com>
Reported-by: default avatarkernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202412290924.UTP7GH2Z-lkp@intel.com/


Suggested-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarMuchun Song <muchun.song@linux.dev>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarShakeel Butt <shakeel.butt@linux.dev>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Jingxiang Zeng <linuszeng@tencent.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f9aad622

mm/list_lru.c

+9 −6
Original line number Diff line number Diff line
@@ -510,7 +510,7 @@ int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru, 
			 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_cgroup *memcg, struct list_lru *lru, 
			parent = parent_mem_cgroup(pos);

		}



		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_cgroup *memcg, struct list_lru *lru, 
			}

			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