linux-kernel - Re: [PATCH v6 00/11] Use obj_cgroup APIs to charge the LRU pages

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Message-Id: <20220703162340.cb90924355dacbb7437ab595@linux-foundation.org>
Date:   Sun, 3 Jul 2022 16:23:40 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Muchun Song <songmuchun@...edance.com>
Cc:     hannes@...xchg.org, longman@...hat.com, mhocko@...nel.org,
        roman.gushchin@...ux.dev, shakeelb@...gle.com,
        cgroups@...r.kernel.org, duanxiongchun@...edance.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Yosry Ahmed <yosryahmed@...gle.com>
Subject: Re: [PATCH v6 00/11] Use obj_cgroup APIs to charge the LRU pages

On Tue, 21 Jun 2022 20:56:47 +0800 Muchun Song <songmuchun@...edance.com> wrote:

> This version is rebased on mm-unstable. Hopefully, Andrew can get this series
> into mm-unstable which will help to determine whether there is a problem or
> degradation. I am also doing some benchmark tests in parallel.
> 
> Since the following patchsets applied. All the kernel memory are charged
> with the new APIs of obj_cgroup.
> 
> 	commit f2fe7b09a52b ("mm: memcg/slab: charge individual slab objects instead of pages")
> 	commit b4e0b68fbd9d ("mm: memcontrol: use obj_cgroup APIs to charge kmem pages")
> 
> But user memory allocations (LRU pages) pinning memcgs for a long time -
> it exists at a larger scale and is causing recurring problems in the real
> world: page cache doesn't get reclaimed for a long time, or is used by the
> second, third, fourth, ... instance of the same job that was restarted into
> a new cgroup every time. Unreclaimable dying cgroups pile up, waste memory,
> and make page reclaim very inefficient.
> 
> We can convert LRU pages and most other raw memcg pins to the objcg direction
> to fix this problem, and then the LRU pages will not pin the memcgs.
> 
> This patchset aims to make the LRU pages to drop the reference to memory
> cgroup by using the APIs of obj_cgroup. Finally, we can see that the number
> of the dying cgroups will not increase if we run the following test script.
> 
> ...
>

I don't have reviewer or acker tags on a couple of these, but there is
still time - I plan to push this series into mm-stable around July 8.