Re: [PATCH 1/4] sched/topology: SD_ASYM_CPUCAPACITY flag detection

[Qais Yousef]

On 24/07/18 09:37, Morten Rasmussen wrote:
> On Mon, Jul 23, 2018 at 05:07:50PM +0100, Qais Yousef wrote:
> > On 23/07/18 16:27, Morten Rasmussen wrote:
> > > It does increase the cost of things like hotplug slightly and
> > > repartitioning of root_domains a slightly but I don't see how we can
> > > avoid it if we want generic code to set this flag. If the costs are not
> > > acceptable I think the only option is to make the detection architecture
> > > specific.
> > I think hotplug is already expensive and this overhead would be small in
> > comparison. But this could be called when frequency changes if I understood
> > correctly - this is the one I wasn't sure how 'hot' it could be. I wouldn't
> > expect frequency changes at a very high rate because it's relatively
> > expensive too..
> A frequency change shouldn't lead to a flag change or a rebuild of the
> sched_domain hierarhcy. The situations where the hierarchy should be
> rebuild to update the flag is during boot as we only know the amount of
> asymmetry once cpufreq has been initialized, when cpus are hotplugged
> in/out, and when root_domains change due to cpuset reconfiguration. So
> it should be a relatively rare event.


Ah OK I misunderstood that part then.

The series LGTM then.

--
Qais Yousef