linux-kernel - Re: [RFC PATCH v2 3/5] padata: dispatch works on different nodes

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Date: Wed, 27 Dec 2023 18:33:50 +0800
From: Gang Li <gang.li@...ux.dev>
To: Tim Chen <tim.c.chen@...ux.intel.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 Muchun Song <muchun.song@...ux.dev>, Mike Kravetz <mike.kravetz@...cle.com>,
 David Rientjes <rientjes@...gle.com>, David Hildenbrand <david@...hat.com>,
 Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH v2 3/5] padata: dispatch works on different nodes

Hi Tim,

According to queue_work_node, if there are no CPUs available on the
given node, it will schedule to any available CPU.

On 2023/12/18 14:46, Gang Li wrote:
> On 2023/12/13 07:40, Tim Chen wrote:
>>
>>>       list_for_each_entry(pw, &works, pw_list)
>>> -        queue_work(system_unbound_wq, &pw->pw_work);
>>> +        if (job->numa_aware)
>>> +            queue_work_node((++nid % num_node_state(N_MEMORY)),
>>
>> The nid may fall on a NUMA node with only memory but no CPU.  In that 
>> case you
>> may still put the work on the unbound queue. You could end up on one 
>> CPU node for work
>> from all memory nodes without CPU. Is this what you want?  Or you would
>> like to spread them between CPU nodes?
>>
>> Tim
> 
> Hi, thank you for your reminder. My intention was to fully utilize all
> memory bandwidth.
> 
> For memory nodes without CPUs, I also hope to be able to spread them on
> different CPUs.