From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: "Huang, Ying" <ying.huang@intel.com>,
Jagdish Gediya <jvgediya@linux.ibm.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
akpm@linux-foundation.org, baolin.wang@linux.alibaba.com,
dave.hansen@linux.intel.com
Subject: Re: [PATCH] mm: migrate: set demotion targets differently
Date: Wed, 30 Mar 2022 22:47:22 +0530 [thread overview]
Message-ID: <87lewrxsv1.fsf@linux.ibm.com> (raw)
In-Reply-To: <87pmm4c4ys.fsf@yhuang6-desk2.ccr.corp.intel.com>
"Huang, Ying" <ying.huang@intel.com> writes:
> Hi, Jagdish,
>
> Jagdish Gediya <jvgediya@linux.ibm.com> writes:
>
...
>> 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 3
>> 3 4
>> 4 X
>
> For such machine, I think the perfect demotion order is,
>
> node demotion_target
> 0 2, 3
> 1 2, 3
> 2 4
> 3 4
> 4 X
I guess the "equally slow nodes" is a confusing definition here. Now if the
system consists of 2 1GB equally slow memory and the firmware doesn't want to
differentiate between them, firmware can present a single NUMA node
with 2GB capacity? The fact that we are finding two NUMA nodes is a hint
that there is some difference between these two memory devices. This is
also captured by the fact that the distance between 2 and 3 is 40 and not 10.
For that specific topology where the distance between 2 and 3 is 40 and 2
and 4 is 80, the demotion target derived by the new code is better
right?
...
-aneesh
next prev parent reply other threads:[~2022-03-30 17:17 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-29 11:52 [PATCH] mm: migrate: set demotion targets differently Jagdish Gediya
2022-03-29 12:26 ` Baolin Wang
2022-03-29 14:04 ` Jagdish Gediya
2022-03-30 6:37 ` Baolin Wang
2022-03-30 6:54 ` Huang, Ying
2022-03-29 14:31 ` Dave Hansen
2022-03-29 16:46 ` Jagdish Gediya
2022-03-29 22:40 ` Dave Hansen
2022-03-30 6:46 ` Huang, Ying
2022-03-30 16:36 ` Jagdish Gediya
2022-03-31 0:27 ` Huang, Ying
2022-03-31 11:17 ` Jonathan Cameron
2022-03-30 17:17 ` Aneesh Kumar K.V [this message]
2022-03-31 0:32 ` Huang, Ying
2022-03-31 6:45 ` Aneesh Kumar K.V
2022-03-31 7:23 ` Huang, Ying
2022-03-31 8:27 ` Aneesh Kumar K.V
2022-03-31 8:58 ` Huang, Ying
2022-03-31 9:33 ` Baolin Wang
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