linux-kernel - Re: [PATCH RFC 0/1] mm: balancing the node zones occupancy

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Message-ID: <d1590275-b70d-5e09-5047-cc0fa268b583@codeaurora.org>
Date:   Tue, 23 Feb 2021 18:00:01 +0530
From:   Charan Teja Kalla <charante@...eaurora.org>
To:     David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org,
        rientjes@...gle.com, vbabka@...e.cz, mhocko@...e.com,
        mgorman@...hsingularity.net, linux-mm@...ck.org
Cc:     vinmenon@...eaurora.org, sudaraja@...eaurora.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 0/1] mm: balancing the node zones occupancy


Thanks David for the review comments!!

On 2/18/2021 11:46 PM, David Hildenbrand wrote:
>> I would like to start discussion about  balancing the occupancy of
>> memory zones in a node in the system whose imabalance may be caused by
>> migration of pages to other zones during hotremove and then hotadding
>> same memory. In this case there is a lot of free memory in newly hotadd
>> memory which can be filled up by the previous migrated pages(as part of
>> offline/hotremove) thus may free up some pressure in other zones of the
>> node.
> 
> Why is this specific to memory hot(un)plug? I think the problem is more
> generic:
> 
> Assume
> 
> 1. Application 1 allocates a lot of memory and gets ZONE_MOVABLE.
> 2. Application 2 allocates a lot of memory and gets ZONE_NORMAL.
> 3. Application 1 quits.
> 
> Same problem, no?

Thanks for simplifying this problem. Yeah, this looks more generic
problem. But for these type of problems, user/system administrator has
clear view about the state of the system and thus may need to take some
decisions to maintain the the node zones balancing e.g. like this change
where migrate the eligible pages to other zones.

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