linux-kernel - Re: [PATCH 4/4] mm: shrinker: make shrinker not depend on memcg kmem

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Date:   Wed, 12 Jun 2019 10:20:15 -0700
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     ktkhai@...tuozzo.com, kirill.shutemov@...ux.intel.com,
        hannes@...xchg.org, mhocko@...e.com, hughd@...gle.com,
        shakeelb@...gle.com, rientjes@...gle.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] mm: shrinker: make shrinker not depend on memcg kmem



On 6/12/19 3:11 AM, Kirill A. Shutemov wrote:
> On Tue, Jun 11, 2019 at 10:07:54PM -0700, Yang Shi wrote:
>>
>> On 6/11/19 7:52 PM, Kirill A. Shutemov wrote:
>>> On Fri, Jun 07, 2019 at 02:07:39PM +0800, Yang Shi wrote:
>>>> Currently shrinker is just allocated and can work when memcg kmem is
>>>> enabled.  But, THP deferred split shrinker is not slab shrinker, it
>>>> doesn't make too much sense to have such shrinker depend on memcg kmem.
>>>> It should be able to reclaim THP even though memcg kmem is disabled.
>>>>
>>>> Introduce a new shrinker flag, SHRINKER_NONSLAB, for non-slab shrinker,
>>>> i.e. THP deferred split shrinker.  When memcg kmem is disabled, just
>>>> such shrinkers can be called in shrinking memcg slab.
>>> Looks like it breaks bisectability. It has to be done before makeing
>>> shrinker memcg-aware, hasn't it?
>> No, it doesn't break bisectability. But, THP shrinker just can be called
>> with kmem charge enabled without this patch.
> So, if kmem is disabled, it will not be called, right? Then it is
> regression in my opinion. This patch has to go in before 2/4.

I don't think this is a regression. "regression" should mean something 
used to work, but it is broken now. Actually, deferred split shrinker 
never works with memcg.

Anyway, either before 2/4 or after 2/4 looks ok.

>