Re: [PATCH 4/4] nvme-tcp: switch to 'cpu' affinity scope for unbound workqueues

[Hannes Reinecke <hare@suse.de>]

On 7/3/24 16:22, Sagi Grimberg wrote:
> 
> 
> On 03/07/2024 16:50, Hannes Reinecke wrote:
>> We should switch to the 'cpu' affinity scope when using the 'wq_unbound'
>> parameter as this allows us to keep I/O locality and improve performance.
> 
> Can you please describe more why this is better? locality between what?
> 
Well; the default unbound scope is 'cache', which groups the cpu 
according to the cache hierarchy. I want the cpu locality of the 
workqueue items to be preserved as much as possible, so I switched
to 'cpu' here.

I'll get some performance numbers.

> While you mention in your cover letter "comments and reviews are welcome"
> The change logs in your patches are not designed to assist your reviewer.

I spent the last few weeks trying to come up with a solution based on my
original submission, but in the end I gave up as I hadn't been able to
fix the original issue.
This here is a different approach by massaging the 'wq_unbound' 
mechanism, which is not only easier but also has the big advantage that
it actually works :-)
So I did not include a changlog to the previous patchset as this is a 
pretty different approach.
Sorry if this is confusing.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@suse.de                                +49 911 74053 688
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