From: Vlastimil Babka <vbabka@suse.cz>
To: Shakeel Butt <shakeel.butt@linux.dev>,
Jingxiang Zeng <linuszeng@tencent.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org,
hannes@cmpxchg.org, mhocko@kernel.org, roman.gushchin@linux.dev,
muchun.song@linux.dev, chengming.zhou@linux.dev,
kasong@tencent.com, kernel test robot <lkp@intel.com>
Subject: Re: [PATCH] mm/list_lru: make the case where mlru is NULL as unlikely
Date: Fri, 28 Feb 2025 17:30:48 +0100 [thread overview]
Message-ID: <a362bf41-afb0-491b-a185-9860b304fb91@suse.cz> (raw)
In-Reply-To: <ngowzrpvvfklkyswlcg7x6gfiqjhxaankkx3jgo3pmvrbzbzdv@jqwfqbjxxvv3>
On 2/25/25 17:23, Shakeel Butt wrote:
> On Tue, Feb 25, 2025 at 11:30:20PM +0800, Jingxiang Zeng wrote:
>> mm/list_lru.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/list_lru.c b/mm/list_lru.c
>> index 064d2018e265..e7e13513ff8e 100644
>> --- a/mm/list_lru.c
>> +++ b/mm/list_lru.c
>> @@ -552,7 +552,7 @@ static int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru)
>> }
>> xas_unlock_irqrestore(&xas, flags);
>> } while (xas_nomem(&xas, GFP_KERNEL));
>> - if (mlru)
>> + if (unlikely(mlru))
>> kfree(mlru);
>
> The report is saying not to check at all. So, just remove the check and
> simply call kfree(mlru) as it handles the NULL check efficiently.
BTW, if it's unlikely to be !NULL then it's not really efficient to call
kfree() unconditionally as it's a function call and those are more expensive
than inline check (especially with spectre mitigations).
next prev parent reply other threads:[~2025-02-28 16:30 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-25 15:30 Jingxiang Zeng
2025-02-25 16:23 ` Shakeel Butt
2025-02-26 1:11 ` Johannes Weiner
2025-02-26 2:09 ` jingxiang zeng
2025-02-26 21:08 ` Shakeel Butt
2025-02-27 8:03 ` jingxiang zeng
2025-02-28 16:30 ` Vlastimil Babka [this message]
2025-02-28 16:33 ` Vlastimil Babka
2025-02-28 18:48 ` Shakeel Butt
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