On Fri, 2012-07-06 at 14:09 -0600, Khalid Aziz wrote: > 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? Yes, offlining and eject are similar operations to a core as it alone cannot be removed physically. Ejecting a core is a logical eject operation, which updates the status (_STA) of the object in ACPI after offlining. The difference from the offlining is that the ejected core is no longer assigned to the partition. Here is one example. Say, a core is assigned to a guest partition as a dedicated resource (ex. 100% of its CPU time is bound to the partition). Offlining this core saves the power-consumption, but this core is still bound to the partition. Ejecting the core removes it from the partition (logically), and allows it to be assigned to other partition as a dedicated resource with hot-add. > 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? It depends on the firmware implementation, but typically the answer is no. _EJ0 of a core object only removes the associated core object. It will require a separate socket hot-remove request to eject the socket-level resources. That is, the OS may not call _EJ0 of a socket object from the core hot-remove operation just because all children cores are removed. Thanks, -Toshi -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
