linux-kernel - Re: [RFC PATCH 2/2] mm/vmscan.c: Prevent allocating shrinker

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Message-ID: <d4f281e6-1999-a3de-b879-c6ca6a25ae67@redhat.com>
Date:   Mon, 6 Dec 2021 15:08:10 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Nico Pache <npache@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, akpm@...ux-foundation.org, shakeelb@...gle.com,
        ktkhai@...tuozzo.com, shy828301@...il.com, guro@...com,
        vbabka@...e.cz, vdavydov.dev@...il.com, raquini@...hat.com
Subject: Re: [RFC PATCH 2/2] mm/vmscan.c: Prevent allocating shrinker_info on
 offlined nodes


>> But there might be more missing. Onlining a new zone will get more
>> expensive in setups with a lot of possible nodes (x86-64 shouldn't
>> really be an issue in that regard).
> 
> Honestly, I am not really concerned by platforms with too many nodes
> without any memory. If they want to shoot their feet then that's their
> choice. We can optimize for those if they ever prove to be standar.
>  
>> If we want stable backports, we'll want something simple upfront.
> 
> For stable backports I would be fine by doing your NODE_DATA check in
> the allocator. In upstream I think we should be aiming for a more robust
> solution that is also easier to maintain further down the line. Even if
> that is an investment at this momemnt because the initialization code is
> a mess.
> 

Agreed. I would be curious *why* we decided to dynamically allocate the
pgdat. is this just a historical coincidence or was there real reason to
not allocate it for all possible nodes during boot?

-- 
Thanks,

David / dhildenb