Re: [PATCH v3] powercap/rapl: reduce ipi calls

[Thomas Gleixner]

On Wed, 17 Feb 2016, Jacob Pan wrote:
> On Wed, 17 Feb 2016 17:04:41 +0100 (CET)
> Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> 
> > > >  
> > > >  	for_each_online_cpu(i) {
> > > >  		if (topology_physical_package_id(i) ==
> > > > package_id)  
> > 
> > This is still crap. We really want a proper handling for that which
> > does not require these silly for_each_cpu() loops.
> > 
> > That code already has a hotplug notifier, so you can track one online
> > cpu in the package like we do in cqm and other facilities.
> > 
> > The first online cpu of a package sets itself as 'owner'. On unplug
> > it looks up:
> > 
> > 	rpl->cpu = cpumask_any_but(topology_core_cpumask(cpu), cpu);
> > 
> > So if this is the last cpu then rpl->cpu becomes nr_cpu_ids.
> > 
> > So that whole nonsense can be avoided completely.
> ok, that would work nicely, similar to cqm_pick_event_reader().
> thanks for the tip. just fyi, unlike perf cqm, rapl runtime change is
> expected to be low frequency.

That still does not justify crap like this. And please use the version of pick
reader which I posted a couple of hours ago.

       http://marc.info/?l=linux-kernel&m=145572542221627&w=2

Thanks,

	tglx