On Wed, 2009-09-16 at 21:54 +0530, Dipankar Sarma wrote: > You aren't, I did :) > > No, for this specific case, latency isn't an issue. The issue is - > how do we cede unused vcpus to hypervisor for better energy > management ? > Yes, it can be done by a hypervisor manager telling the kernel to > offline and make a bunch of vcpus "inactive". It does have to choose > offline (release vcpu) vs. inactive (cede but guranteed if needed). > The problem is that long ago we exported a lot of hotplug stuff to > userspace through the sysfs interface and we cannot do something > inside the kernel without keeping the sysfs stuff consistent. > This seems like a sane way to do that without undoing all the > virtual cpu hotplug infrastructure in different supporting archs. > Well, I did bring the latency into the picture. To some extent it -is- a latency issue. Though we aren't talking milliseconds here... if the CPU's been reallocated to another partition we are talking seconds or minutes or more until we can get it back :-)
In any case, this sounds to me like a perfectly valid feature to have, which s390 already does via arch specific hooks, so I fail to see why it wouldn't be legitimate to have a common attribute for it. I don't buy into the layering violation. It's too often a straw man and an excuse for a lack of a proper reason. Cheers, Ben. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
