From: Vlastimil Babka <vbabka@suse.cz>
To: Johannes Weiner <hannes@cmpxchg.org>,
Jingxiang Zeng <jingxiangzeng.cas@gmail.com>
Cc: linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@kernel.org,
roman.gushchin@linux.dev, shakeel.butt@linux.dev,
david@redhat.com, muchun.song@linux.dev,
chengming.zhou@linux.dev, kasong@tencent.com, lkp@intel.com,
Zeng Jingxiang <linuszeng@tencent.com>
Subject: Re: [PATCH] mm/list_lru: allocate on first insert instead of allocation
Date: Fri, 28 Feb 2025 18:18:05 +0100 [thread overview]
Message-ID: <e9adf6e8-d373-4429-8f4b-1e0b41c5df58@suse.cz> (raw)
In-Reply-To: <20250228163437.GA120597@cmpxchg.org>
On 2/28/25 17:34, Johannes Weiner wrote:
> On Fri, Feb 28, 2025 at 07:38:36PM +0800, Jingxiang Zeng wrote:
>> @@ -84,6 +86,9 @@ lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
>> spin_unlock_irq(&l->lock);
>> else
>> spin_unlock(&l->lock);
>> + } else {
>> + if (!memcg_list_lru_alloc(memcg, lru))
>> + goto again;
>> }
>
> Unfortunately, you can't do allocations from this path :(
>
> list_lru_add() is called from many places with spinlocks, rcu locks
> etc. held.
Aww, I was hoping we'd get rid of all the plumbing of lru through the slab
allocator.
But maybe we could, anyway? In __memcg_slab_post_alloc_hook() AFAICS the
only part that lru handling reuses is the objcg pointer. Moving the code to
kmem_cache_alloc_lru() would mean just another current_obj_cgroup() lookup
and that's not that expensive in the likely() cases, or is it?
next prev parent reply other threads:[~2025-02-28 17:18 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-28 11:38 Jingxiang Zeng
2025-02-28 16:34 ` Johannes Weiner
2025-02-28 17:18 ` Vlastimil Babka [this message]
2025-02-28 22:05 ` Vlastimil Babka
2025-03-01 18:32 ` Vlastimil Babka
2025-03-03 4:58 ` Kairui Song
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