Re: Selecting CPUs for queuing work on

[Tejun Heo]

On Fri, Aug 12, 2022 at 04:26:47PM -0400, Felix Kuehling wrote:
> Hi workqueue maintainers,
> 
> In the KFD (amdgpu) driver we found a need to schedule bottom half interrupt
> handlers on CPU cores different from the one where the top-half interrupt
> handler runs to avoid the interrupt handler stalling the bottom half in
> extreme scenarios. See my latest patch that tries to use a different
> hyperthread on the same CPU core, or falls back to a different core in the
> same NUMA node if that fails:
> https://lore.kernel.org/all/20220811190433.1213179-1-Felix.Kuehling@xxxxxxx/
> 
> Dave pointed out that the driver may not be the best place to implement such
> logic and suggested that we should have an abstraction, maybe in the
> workqueue code. Do you feel this is something that could or should be
> provided by the core workqueue code? Or maybe some other place?

I'm not necessarily against it. I guess it can be a flag on an unbound wq.
Do the interrupts move across different CPUs tho? ie. why does this need to
be a dynamic decision?

Thanks.

-- 
tejun