From: Muchun Song <songmuchun@bytedance.com>
To: "Michal Koutný" <mkoutny@suse.com>
Cc: Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Shakeel Butt <shakeelb@google.com>, Roman Gushchin <guro@fb.com>,
Yang Shi <shy828301@gmail.com>, Alex Shi <alexs@kernel.org>,
Wei Yang <richard.weiyang@gmail.com>,
Dave Chinner <david@fromorbit.com>,
trond.myklebust@hammerspace.com, anna.schumaker@netapp.com,
jaegeuk@kernel.org, chao@kernel.org,
Kari Argillander <kari.argillander@gmail.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
linux-nfs@vger.kernel.org, Qi Zheng <zhengqi.arch@bytedance.com>,
Xiongchun duan <duanxiongchun@bytedance.com>,
Fam Zheng <fam.zheng@bytedance.com>,
Muchun Song <smuchun@gmail.com>
Subject: Re: [PATCH v5 10/16] mm: list_lru: allocate list_lru_one only when needed
Date: Fri, 21 Jan 2022 13:28:05 +0800 [thread overview]
Message-ID: <CAMZfGtV4mxn0pqna0BsNAP4eLA7UD-gOJ2XCPU2O0C7VcUJa0g@mail.gmail.com> (raw)
In-Reply-To: <20220119093311.GD15686@blackbody.suse.cz>
On Wed, Jan 19, 2022 at 5:33 PM Michal Koutný <mkoutny@suse.com> wrote:
>
> On Tue, Jan 18, 2022 at 08:05:44PM +0800, Muchun Song <songmuchun@bytedance.com> wrote:
> > I have thought about this. It's a little different to rely on objcg
> > reparenting since the user can get memcg from objcg and
> > then does not realize the memcg has reparented.
>
> When you pointed that out, I'm now also wondering how
> memcg_list_lru_alloc() would be synchronized against
> reparenting/renumbering of kmemcg_ids. What I suspect is that newly
> allocated mlru may be stored into the xarray with a stale kmemcg_id.
The synchronization is based on the lock of list_lru->lock.
memcg_list_lru_free() will help us do housekeeping.
>
> > Maybe holding css_set_lock can do that. I do not think this
> > is a good choice.
>
> I agree, it doesn't sound well.
>
> > Do you have any thoughts about this?
>
> Thoughts / questions of what I don't undestand well:
> - Why do you allocate mlrus for all ancestors in memcg_list_lru_alloc()?
It's because we need to be reparenting.
> - It'd be sufficient to allocate just for the current memcg.
> - Possibly allocate ancestors upon reparenting (to simplify the
> allocation from slab_pre_alloc_hook itself).
I agree it is nice to only allocate for current memcg, but
reparenting cannot handle failure of memory allocation.
>
> - What is the per-kmemcg_id lookup good for?
> - I observe most calls of list_lru_from_memcg_idx() come from callers
> that know memcg (or even objcg).
> - The non-specific use case seems list_lru_walk_node() working with
> per-node and not per-memcg projection.
> - Consequently that is only used over all nodes anyway
> (list_lru_walk().
> - The idea behind this question is -- attach the list_lrus to
> obj_cgroup (and decommission the kmemcg_id completely).
> (Not necessarily part of this series but independent approach.)
>
I have some questions about this thought.
We would attach more than one list_lrus to obj_cgroup,
right? How to arrange those list_lrus, array or linked-list?
Thanks.
next prev parent reply other threads:[~2022-01-21 5:28 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-20 8:56 [PATCH v5 00/16] Optimize list lru memory consumption Muchun Song
2021-12-20 8:56 ` [PATCH v5 01/16] mm: list_lru: optimize memory consumption of arrays of per cgroup lists Muchun Song
2022-01-07 0:05 ` Roman Gushchin
2022-01-09 4:49 ` Muchun Song
2022-01-10 18:42 ` Roman Gushchin
2022-01-11 3:19 ` Muchun Song
2021-12-20 8:56 ` [PATCH v5 02/16] mm: introduce kmem_cache_alloc_lru Muchun Song
2022-01-07 3:04 ` Roman Gushchin
2022-01-09 6:21 ` Muchun Song
2022-01-10 18:47 ` Roman Gushchin
2022-01-11 15:41 ` Vlastimil Babka
2022-01-11 17:54 ` Roman Gushchin
2021-12-20 8:56 ` [PATCH v5 03/16] fs: introduce alloc_inode_sb() to allocate filesystems specific inode Muchun Song
2022-01-11 18:55 ` Roman Gushchin
2022-01-12 2:54 ` Muchun Song
2021-12-20 8:56 ` [PATCH v5 04/16] fs: allocate inode by using alloc_inode_sb() Muchun Song
2022-01-11 18:58 ` Roman Gushchin
2022-01-12 2:55 ` Muchun Song
2021-12-20 8:56 ` [PATCH v5 05/16] f2fs: " Muchun Song
2022-01-11 19:03 ` Roman Gushchin
2021-12-20 8:56 ` [PATCH v5 06/16] nfs42: use a specific kmem_cache to allocate nfs4_xattr_entry Muchun Song
2021-12-20 8:56 ` [PATCH v5 07/16] mm: dcache: use kmem_cache_alloc_lru() to allocate dentry Muchun Song
2022-01-11 19:05 ` Roman Gushchin
2021-12-20 8:56 ` [PATCH v5 08/16] xarray: use kmem_cache_alloc_lru to allocate xa_node Muchun Song
2022-01-11 19:14 ` Roman Gushchin
2021-12-20 8:56 ` [PATCH v5 09/16] mm: memcontrol: move memcg_online_kmem() to mem_cgroup_css_online() Muchun Song
2022-01-11 19:17 ` Roman Gushchin
2021-12-20 8:56 ` [PATCH v5 10/16] mm: list_lru: allocate list_lru_one only when needed Muchun Song
2022-01-06 11:00 ` Michal Koutný
2022-01-12 13:22 ` Muchun Song
2022-01-13 13:32 ` Michal Koutný
2022-01-18 12:05 ` Muchun Song
2022-01-19 9:33 ` Michal Koutný
2022-01-21 5:28 ` Muchun Song [this message]
2022-01-11 20:00 ` Roman Gushchin
2022-01-12 4:48 ` Muchun Song
2021-12-20 8:56 ` [PATCH v5 11/16] mm: list_lru: rename memcg_drain_all_list_lrus to memcg_reparent_list_lrus Muchun Song
2021-12-20 8:56 ` [PATCH v5 12/16] mm: list_lru: replace linear array with xarray Muchun Song
2021-12-20 8:56 ` [PATCH v5 13/16] mm: memcontrol: reuse memory cgroup ID for kmem ID Muchun Song
2021-12-20 9:27 ` Mika Penttilä
2022-01-05 17:03 ` Michal Koutný
2022-01-06 3:34 ` Muchun Song
2021-12-20 8:56 ` [PATCH v5 14/16] mm: memcontrol: fix cannot alloc the maximum memcg ID Muchun Song
2021-12-20 8:56 ` [PATCH v5 15/16] mm: list_lru: rename list_lru_per_memcg to list_lru_memcg Muchun Song
2021-12-20 8:56 ` [PATCH v5 16/16] mm: memcontrol: rename memcg_cache_id to memcg_kmem_id Muchun Song
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