Re: [PATCH] ACPI: Add ACPI CPU hot-remove support

From: Khalid Aziz
Date: Fri Jul 06 2012 - 16:09:19 EST

On 07/06/2012 01:13 PM, Toshi Kani wrote:

For step 2) and 4), I am wondering if they are relevant to CPU hotplug
these days. In ACPI namespace, a processor object represents a logical
processor (or a core when hyper-threading is disabled). A physical
processor (i.e. a socket) usually has multiple cores, and memory
controller and bus interface are part of the socket functionality.
Hence, I think step 2) and 4) belong to socket-level hot-removal
operation, which can be implemented as container hot-remove when a
socket is represented with a container object.

What does it mean to eject just a core in that case? If there are seven
other cores in the physical processor and you get a request to eject
one core, what would you expect kernel to do - simply move all processes
and interrupts off of that core, take it out of scheduling consideration
and simply idle the core? If yes, how is that any different from simply
offlining a core? If you are ejecting individual cores at a time, do you
keep track of how many you have ejected and then eject the entire physical
CPU along with memory and IOH associated with the socket when the last
core is ejected?

Khalid Aziz Unix Systems Lab
(970)898-9214 Hewlett-Packard
khalid.aziz@xxxxxx Fort Collins, CO

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