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Date: Thu, 14 Apr 2022 15:09:42 +0800
From: "ying.huang@...el.com" <ying.huang@...el.com>
To: Jagdish Gediya <jvgediya@...ux.ibm.com>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Cc: akpm@...ux-foundation.org, aneesh.kumar@...ux.ibm.com,
baolin.wang@...ux.alibaba.com, dave.hansen@...ux.intel.com
Subject: Re: [PATCH v2 1/5] mm: demotion: Set demotion list differently
On Wed, 2022-04-13 at 14:52 +0530, Jagdish Gediya wrote:
> Sharing used_targets between multiple nodes in a single
> pass limits some of the opportunities for demotion target
> sharing.
>
> Don't share the used targets between multiple nodes in a
> single pass, instead accumulate all the used targets in
> source nodes shared by all pass, and reset 'used_targets'
> to source nodes while finding demotion targets for any new
> node.
>
> This results into some more opportunities to share demotion
> targets between multiple source nodes, e.g. with below NUMA
> topology, where node 0 & 1 are cpu + dram nodes, node 2 & 3
> are equally slower memory only nodes, and node 4 is slowest
> memory only node,
>
> available: 5 nodes (0-4)
> node 0 cpus: 0 1
> node 0 size: n MB
> node 0 free: n MB
> node 1 cpus: 2 3
> node 1 size: n MB
> node 1 free: n MB
> node 2 cpus:
> node 2 size: n MB
> node 2 free: n MB
> node 3 cpus:
> node 3 size: n MB
> node 3 free: n MB
> node 4 cpus:
> node 4 size: n MB
> node 4 free: n MB
> node distances:
> node 0 1 2 3 4
> 0: 10 20 40 40 80
> 1: 20 10 40 40 80
> 2: 40 40 10 40 80
> 3: 40 40 40 10 80
> 4: 80 80 80 80 10
>
> The existing implementation gives below demotion targets,
>
> node demotion_target
> 0 3, 2
> 1 4
> 2 X
> 3 X
> 4 X
>
> With this patch applied, below are the demotion targets,
>
> node demotion_target
> 0 3, 2
> 1 3, 2
> 2 4
> 3 4
> 4 X
>
> e.g. with below NUMA topology, where node 0, 1 & 2 are
> cpu + dram nodes and node 3 is slow memory node,
>
> available: 4 nodes (0-3)
> node 0 cpus: 0 1
> node 0 size: n MB
> node 0 free: n MB
> node 1 cpus: 2 3
> node 1 size: n MB
> node 1 free: n MB
> node 2 cpus: 4 5
> node 2 size: n MB
> node 2 free: n MB
> node 3 cpus:
> node 3 size: n MB
> node 3 free: n MB
> node distances:
> node 0 1 2 3
> 0: 10 20 20 40
> 1: 20 10 20 40
> 2: 20 20 10 40
> 3: 40 40 40 10
>
> The existing implementation gives below demotion targets,
>
> node demotion_target
> 0 3
> 1 X
> 2 X
> 3 X
>
> With this patch applied, below are the demotion targets,
>
> node demotion_target
> 0 3
> 1 3
> 2 3
> 3 X
>
With the [PATCH v1], you have describe the demotion order changes for
the following system, I guess there's no change with [PATCH v2]?
With below NUMA topology, where node 0 & 2 are cpu + dram
nodes and node 1 & 3 are slow memory nodes,
available: 4 nodes (0-3)
node 0 cpus: 0 1
node 0 size: n MB
node 0 free: n MB
node 1 cpus:
node 1 size: n MB
node 1 free: n MB
node 2 cpus: 2 3
node 2 size: n MB
node 2 free: n MB
node 3 cpus:
node 3 size: n MB
node 3 free: n MB
node distances:
node 0 1 2 3
0: 10 40 20 80
1: 40 10 80 80
2: 20 80 10 40
3: 80 80 40 10
And, what is the demotion order for the following system with [PATCH
v2]?
Node 0 & 2 are cpu + dram nodes and node 1 are slow
memory node near node 0,
available: 3 nodes (0-2)
node 0 cpus: 0 1
node 0 size: n MB
node 0 free: n MB
node 1 cpus:
node 1 size: n MB
node 1 free: n MB
node 2 cpus: 2 3
node 2 size: n MB
node 2 free: n MB
node distances:
node 0 1 2
0: 10 40 20
1: 40 10 80
2: 20 80 10
Best Regards,
Huang, Ying
[snip]
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