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

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Date:   Sat, 23 Nov 2019 01:36:13 +0800
From:   Pengfei Li <fly@...nel.page>
To:     Christopher Lameter <cl@...ux.com>
Cc:     David Hildenbrand <david@...hat.com>, 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, fly@...nel.page
Subject: Re: [RFC v1 00/19] Modify zonelist to nodelist v1

On Fri, 22 Nov 2019 15:53:57 +0000 (UTC)
Christopher Lameter <cl@...ux.com> 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.
> 

Thanks for your comments.

Yes, I will add detailed performance test data in v2.

> > 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.

Sorry, I forgot to mention that the information about the zones that
are available to the node is still there.

The old for_each_zone_zonelist has been replaced with
for_each_zone_nodelist.

I will add some key implementation details in v2. 

> 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.
> 

I'm not sure if I understand what you mean, but since commit
c9bff3eebc09 ("mm, page_alloc: rip out ZONELIST_ORDER_ZONE"), the
zonelist is always in "Node" order, so building the nodelist is fine.

-- 
Pengfei