On Mon, Aug 07, 2017 at 01:41:38PM +0000, Ofer Levi(SW) wrote: > > 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.
But who is doing actual hotplug? Why would you ever unplug or plug a CPU in a time critical situation? > > 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. Doesn't make sense. If you look at smp_init() boot brings up the CPUs one at a time. So how can boot be different than hot-pugging them?