Re: [PATCH 0/3] cpu: idle state framework for offline CPUs.

[Shaohua Li]

Hi,

On Wed, Aug 05, 2009 at 10:25:53PM +0800, Gautham R Shenoy wrote:
> In this patch-series, we propose to extend the CPU-Hotplug infrastructure
> and allow the system administrator to choose the desired state the CPU should
> go to when it is offlined. We think this approach addresses the concerns about
> determinism as well as transparency, since CPU-Hotplug already provides
> notification mechanism which the userspace can listen to for any change
> in the configuration and correspondingly readjust any previously set
> cpu-affinities.
Peter dislikes any approach (including cpuhotplug) which breaks userspace policy,
even userspace can get a notification.

> Also, approaches such as [1] can make use of this
> extended infrastructure instead of putting the CPU to an arbitrary C-state
> when it is offlined, thereby providing the system administrator a rope to hang
> himself with should he feel the need to do so.
I didn't see the reason why administrator needs to know which state offline cpu
should stay. Don't know about powerpc side, but in x86 side, it appears deepest
C-state is already preferred.

Thanks,
Shaohua
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