> You've failed to explain why you think hotplug should be a performance > critical path. 1. hotplug bring up of 4K cpus takes 40 minutes. Way too much for any user. 2. plat-eznps is a network processor, where bring up time is sensitive.
> I'm also not seeing how it would be different from boot; you'd be > looking at a similar cost for SMP bringup. bring up time of 4k cpus during kernel boot takes 4.5 minutes. The function in question is performed only when smp init was performed. If I understand correctly, whatever this function is doing is performed after all cpus were brought up during kernel boot. Thanks -Ofer On Monday, August 7, 2017 11:34 AM +0000, Peter Zijlstra wrote: > On Sun, Aug 06, 2017 at 05:53:37AM +0000, Ofer Levi(SW) wrote: > > I'm adding hot-plug support for the above arch and ran into performance > issue with execution of > > partition_sched_domains () - About 0.5 sec per cpu, which is unacceptable > with the arch supported 4k cpus. > > To my limited understanding, on the plat-eznps arch, where each cpu is > always running a single threaded process in > > isolation mode, the above call is not necessary, > > Can you please confirm (or reject) my understanding? If I'm wrong short > explanation will be appreciated. > > If I'm correct, I will be grateful if you can point me to how to skip this > > call in > a way acceptable by community. > > You've failed to explain why you think hotplug should be a performance > critical path. > > I'm also not seeing how it would be different from boot; you'd be > looking at a similar cost for SMP bringup.
