Re: [PATCH 3/4] workqueue: introduce helper workqueue_unbound_affinity_scope()

[Tejun Heo <tj@kernel.org>]

Hello, Hannes.

On Wed, Jul 03, 2024 at 03:50:20PM +0200, Hannes Reinecke wrote:
> For drivers creating their own workqueue it might be useful to
> switch to the 'cpu' unbound affinity scope to keep the locality
> and reduce contention. As it's cumbersome to instruct the user
> how to switch to affinity scope from userland introduce a helper
> workqueue_unbound_affinity_scope() to let the driver set the
> affinity scope directly.

So, there's already apply_workqueue_attrs() to change the unbound workqueue
attributes including affinity scope. It's cumbersome to use because the
attribute structure has to be allocated and then freed. The alloc/free is
for the cpumasks, so if the API is too cumbersome, maybe we can just make
the cpumask part optional? ie. Allow using workqueue_attrs without going
through alloc if cpumasks don't need to be modified. There probably should
be a function to read attrs from a workqueue too.

Thanks.

-- 
tejun