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

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Message-ID: <1bb37491-72a7-feaa-722d-a5825813a409@redhat.com>
Date:   Fri, 22 Nov 2019 11:03:30 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Pengfei Li <fly@...nel.page>, akpm@...ux-foundation.org
Cc:     mgorman@...hsingularity.net, mhocko@...nel.org, vbabka@...e.cz,
        cl@...ux.com, 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 21.11.19 16:17, Pengfei Li wrote:
> Motivation
> ----------
> Currently if we want to iterate through all the nodes we have to
> traverse all the zones from the zonelist.
> 
> So in order to reduce the number of loops required to traverse node,
> this series of patches modified the zonelist to nodelist.
> 
> Two new macros have been introduced:
> 1) for_each_node_nlist
> 2) for_each_node_nlist_nodemask
> 
> 
> Benefit
> -------
> 1. For a NUMA system with N nodes, each node has M zones, the number
>     of loops is reduced from N*M times to N times when traversing node.
> 
> 2. The size of pg_data_t is much reduced.
> 
> 
> Test Result
> -----------
> Currently I have only performed a simple page allocation benchmark
> test on my laptop, and the results show that the performance of a
> system with only one node is almost unaffected.
> 

So you are seeing no performance changes. I am wondering why do we need 
this, then - because your motivation sounds like a performance 
improvement? (not completely against this, just trying to understand the 
value of this :) )


-- 

Thanks,

David / dhildenb