On Mon, Aug 22, 2011 at 5:21 PM, Christian Robottom Reis kiko@linaro.org wrote:
On Mon, Aug 22, 2011 at 11:18:52AM -0300, Christian Robottom Reis wrote:
On Fri, Aug 19, 2011 at 12:38:13PM -0700, Mike Turquette wrote:
This series is posted for posterity. It has been NAK'd by the community since CPU hotplug has been deemed an inappropriate mechanism for power capping.
I spoke with Amit about this last week. What's the plan going forward on really saving power when a CPU isn't being used -- just ensuring the lowest possible idle state is really off?
And are there situations where the hardware requires something like hotplug to actually maximize savings?
Oh, and finally, it seems that patches 1-3 might be useful, regardless of the NAKing of the actual patchset, right?
No, those were NACK'ed as well. The interface is not be 'enhanced' in any way that might promote it's use for power savings.
Peter's actual message below:
"Nacked-by: Peter Zijlstra a.p.zijlstra@chello.nl
the kernel really shouldn't be using hotplug for this (nor should userspace really). hot-unplugging random cpus wrecks things like cpusets. Furthermore hotplug does way too much work to use as a simple means to idle a cpu.
Even the availability of this mask is wrong, since that implies the information is useful, which per the above it is not, the kernel shouldn't care about this full-stop.
The only reason for the OS to unplug a CPU is imminent and unavoidable hardware failure. Thermal capping is not that (and yes ACPI-4.0 is a broken piece of shit)."