linux-kernel - Re: [PATCH 2/2] mm: move the high field from struct mem_cgroup to page

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Message-ID: <20180420205450.GB24563@cmpxchg.org>
Date:   Fri, 20 Apr 2018 16:54:50 -0400
From:   Johannes Weiner <hannes@...xchg.org>
To:     Roman Gushchin <guro@...com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        cgroups@...r.kernel.org, kernel-team@...com,
        Michal Hocko <mhocko@...e.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 2/2] mm: move the high field from struct mem_cgroup to
 page_counter

On Fri, Apr 20, 2018 at 05:36:32PM +0100, Roman Gushchin wrote:
> We do store memory.min, memory.low and memory.max actual values
> in struct page_counter fields, while memory.high value is located
> in the struct mem_cgroup directly, which is not very consistent.
> 
> This patch moves the high field from struct mem_cgroup to
> struct page_counter to simplify the code and make handling
> of all limits/boundaries clearer.

I would prefer not doing this.

Yes, it looks a bit neater if all these things are next to each other
in the struct, but on the other hand it separates the high variable
from high_work, and it adds an unnecessary setter function as well.

Plus, nothing in the page_counter code actually uses the value, it
really isn't part of that abstraction layer.