Re: [PATCH 3/4] workqueue: add schedule_on_each_cpumask helper

[Michal Hocko]

On Fri 02-06-23 14:04:28, Marcelo Tosatti wrote:
> On Fri, Jun 02, 2023 at 12:48:23PM +0200, Michal Hocko wrote:
[...]
> > > +	if (!alloc_cpumask_var(&effmask, GFP_KERNEL)) {
> > > +		free_percpu(works);
> > > +		return -ENOMEM;
> > > +	}
> > > +
> > > +	cpumask_and(effmask, cpumask, cpu_online_mask);
> > > +
> > > +	cpus_read_lock();
> > > +
> > > +	for_each_cpu(cpu, effmask) {
> > 
> > Is the cpu_online_mask dance really necessary? 
> 
> > Why cannot you simply do for_each_online_cpu here? 
> 
> Are you suggesting to do: 
> 
> 	for_each_online_cpu(cpu) {
> 		if cpu is not in cpumask
> 			continue;
> 		...
> 	}
> 
> This does not seem efficient.

Are you sure this is less sufficient than a memory allocation?
-- 
Michal Hocko
SUSE Labs