linux-kernel - Re: [RFC v1 00/19] Modify zonelist to nodelist v1

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Message-ID: <5eea4eca-d359-fcee-9bf0-9ee3501bdb2e@redhat.com>
Date:   Fri, 22 Nov 2019 17:06:24 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Christopher Lameter <cl@...ux.com>, Pengfei Li <fly@...nel.page>
Cc:     akpm@...ux-foundation.org, mgorman@...hsingularity.net,
        mhocko@...nel.org, vbabka@...e.cz, iamjoonsoo.kim@....com,
        guro@...com, linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [RFC v1 00/19] Modify zonelist to nodelist v1

On 22.11.19 16:53, Christopher Lameter wrote:
> On Fri, 22 Nov 2019, Pengfei Li wrote:
> 
>> I am sorry that I did not make it clear. I want to express this series
>> of patches will benefit NUMA systems with multiple nodes.
> 
> Ok but that benefit needs to be quantified somehow.
> 
>> The main benefit is that it will be more efficient when traversing all
>> nodes (for example when performing page reclamation).
> 
> And you loose the prioritization of allocations through these different
> zones. We create zonelists with a certain sequence of the zones in
> order to prefer allocations from certain zones. This is in particular
> important for the smaller DMA zones which may be easily exhausted.
> 

That's an important point also when MOVABLE is in place. You really
don't want to go to random other zones before considering all MOVABLE
zones. Same with DMA and NORMAL.

-- 

Thanks,

David / dhildenb