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Sender: Tejun Heo <htejun@gmail.com>
Date:   Fri, 19 Aug 2022 06:29:22 -1000
From:   Tejun Heo <tj@kernel.org>
To:     "zhaoyang.huang" <zhaoyang.huang@unisoc.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>,
        Zhaoyang Huang <huangzhaoyang@gmail.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        ke.wang@unisoc.com, Zefan Li <lizefan.x@bytedance.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Shakeel Butt <shakeelb@google.com>,
        Muchun Song <songmuchun@bytedance.com>
Subject: Re: [RFC PATCH] memcg: use root_mem_cgroup when css is inherited
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On Fri, Aug 19, 2022 at 07:29:22PM +0800, zhaoyang.huang wrote:
> From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> 
> It is observed in android system where per-app cgroup is demanded by freezer
> subsys and part of groups require memory control. The hierarchy could be simplized
> as bellowing where memory charged on group B abserved while we only want have
> group E's memory be controlled and B's descendants compete freely for memory.
> This should be the consequences of unified hierarchy.
> Under this scenario, less efficient memory reclaim is observed when comparing
> with no memory control. It is believed that multi LRU scanning introduces some
> of the overhead. Furthermore, page thrashing is also heavier than global LRU
> which could be the consequences of partial failure of WORKINGSET mechanism as
> LRU is too short to protect the active pages.
> 
> A(subtree_control = memory) - B(subtree_control = NULL) - C()
> 							\ D()
> 			    - E(subtree_control = memory) - F()
> 							  \ G()
> 
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com>

Just in case it wasn't clear.

Nacked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun