Re: [PATCH 2/2] workqueue:Fix affinity of an unbound worker of a node with 1 online CPU

On Wed, 2016-06-15 at 12:01 -0400, Tejun Heo wrote:

On Wed, Jun 15, 2016 at 03:14:15PM +0200, Peter Zijlstra wrote:

quoted

On Wed, Jun 15, 2016 at 06:20:33PM +0530, Gautham R Shenoy wrote:

quoted

We will no longer have the optimization in
restore_unbound_workers_cpumask() but I suppose we don't lose much by
resetting the affinity every time a CPU in the pool->attr->cpumask
comes online.

Right; optimizing hotplug really isn't worth it. The code needs to be
simple and robust (ha! funny).

The only case it might matter is CPU hotplug being used aggressively
for power saving.  No idea how popular that is now tho.
set_cpus_allowed isn't that expensive and phones don't tend to have
massive number of kworkers, so hopefully it won't show up.

quoted

In any case, Tejun, does this work for you?

I'm not sure about the reordering part but for setting affinity on
each onlining, no objection.  If it ever shows up as performance /
power regression, we can revisit it later.

Peterz do you want to send a SOB'ed patch, or can we take what you posted and
add your SOB?

And Tejun are you happy to merge this for rc4?

cheers