linux-kernel - Re: [v7 PATCH 09/12] mm: vmscan: use per memcg nr

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Message-ID: <1d751688-12a9-a5c3-2d9a-c4b9e65c7492@virtuozzo.com>
Date:   Wed, 10 Feb 2021 17:36:56 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     Yang Shi <shy828301@...il.com>, Roman Gushchin <guro@...com>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        Shakeel Butt <shakeelb@...gle.com>,
        Dave Chinner <david@...morbit.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [v7 PATCH 09/12] mm: vmscan: use per memcg nr_deferred of
 shrinker

On 10.02.2021 04:52, Yang Shi wrote:
> On Tue, Feb 9, 2021 at 5:27 PM Roman Gushchin <guro@...com> wrote:
>>
>> On Tue, Feb 09, 2021 at 09:46:43AM -0800, Yang Shi wrote:
>>> Use per memcg's nr_deferred for memcg aware shrinkers.  The shrinker's nr_deferred
>>> will be used in the following cases:
>>>     1. Non memcg aware shrinkers
>>>     2. !CONFIG_MEMCG
>>>     3. memcg is disabled by boot parameter
>>>
>>> Signed-off-by: Yang Shi <shy828301@...il.com>
>>> ---
>>>  mm/vmscan.c | 78 ++++++++++++++++++++++++++++++++++++++++++++---------
>>>  1 file changed, 66 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> index d4b030a0b2a9..748aa6e90f83 100644
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -368,6 +368,24 @@ static void unregister_memcg_shrinker(struct shrinker *shrinker)
>>>       up_write(&shrinker_rwsem);
>>>  }
>>>
>>> +static long count_nr_deferred_memcg(int nid, struct shrinker *shrinker,
>>> +                                 struct mem_cgroup *memcg)
>>
>> "Count" is not associated with xchg() semantics in my head, but I don't know
>> what's the better version. Maybe steal or pop?
> 
> It is used to retrieve the nr_deferred value. I don't think "steal" or
> "pop" helps understand. Actually "count" is borrowed from
> count_objects() method of shrinker.

I'd also voted for another name.

xchg_nr_deferred() or steal/pop sound better for me.