Greg, -----Original Message----- From: Greg KH [mailto:gregkh@linuxfoundation.org] Sent: 20141020 14:48 To: Neil Zhang Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] drivers: base: update cpu offline info when do hotplug On Sun, Oct 19, 2014 at 11:39:23PM -0700, Neil Zhang wrote: >> How much noise is this going to cause on a big/little system that >> constantly hot unplug/plugs processors all of the time? > > Can you explain more what kind of noise will be introduced on a big/little system? Have you tested this on such a machine? I didn't have such kind of machine on hand. Can anyone has such machine to verify it? Thanks! > As I know IKS on arm will use cpu_suspend way to power down a core. Are you sure that it also doesn't use that same functionality to drop a processor to save power? As I know it use cpu_suspend to switch out a processor in IKS and there is no cpu hotplug notifier in this procedure. Why do you need/want this notification? What are you going to do with this information that you don't already have? The offline won't be updated if an in kernel hotplug governor plug in / out a core which cause the sysfs interface report a wrong status. thanks, greg k-h Best Regards, Neil Zhang {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I