Re: [PATCH V5 2/2] tracing, perf : add cpu hotplug trace events

From: Nicolas Pitre
Date: Thu Feb 24 2011 - 15:40:28 EST

On Thu, 24 Feb 2011, Peter Zijlstra wrote:

> On Thu, 2011-02-24 at 15:24 -0500, Nicolas Pitre wrote:
> > Most SMP ARM processors are going to use it soon. Powering down idle
> > cores provides substantial power saving.
> And why can't regular idle paths be used? CPU hotplug is a massively
> expensive operation.

The idle path assumes that the CPU state is preserved. We're talking
about cores completely going down with power pulled beneath them and
eventually rebooted dynamically here.

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