netdev - Re: [PATCH net-next 3/8] ionic: add private workqueue per-device

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Date: Thu, 13 Jun 2024 15:19:28 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: "Nelson, Shannon" <shannon.nelson@....com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
 pabeni@...hat.com, brett.creeley@....com, drivers@...sando.io
Subject: Re: [PATCH net-next 3/8] ionic: add private workqueue per-device

On Thu, 13 Jun 2024 13:38:18 -0700 Nelson, Shannon wrote:
> > little jobs little point of having your own wq, no?
> > At this point of reading the series its a bit unclear why
> > the wq separation is needed.  
> 
> Yes, when using only a single PF or two this doesn't look so bad to be 
> left on the system workqueue.  But we have a couple customers that want 
> to scale out to lots of VFs with multiple queues per VF, which 
> multiplies out 100's of queues getting workitems.  We thought that 
> instead of firebombing the system workqueue with a lot of little jobs, 
> we would give the scheduler a chance to work with our stuff separately, 
> and setting it up by device seemed like an easy enough way to partition 
> the work.  Other options might be one ionic wq used by all devices, or 
> maybe a wq per PF family?  Do you have a preference, or do you still 
> think that the system wq is enough?

No, no, code is fine. I was just complaining about the commit message :)
The math for how many work items you can see in reasonable scenarios
would be helpful to see when judging the need.