On Tue, Sep 15, 2009 at 08:28:34PM +0530, Balbir Singh wrote: > * Peter Zijlstra <a.p.zijls...@chello.nl> [2009-09-15 14:11:41]: > > > On Tue, 2009-09-15 at 17:36 +0530, Gautham R Shenoy wrote: > > > This patchset contains the offline state driver implemented for > > > pSeries. For pSeries, we define three available_hotplug_states. They are: > > > > > > online: The processor is online. > > > > > > offline: This is the the default behaviour when the cpu is > > > offlined > > > even in the absense of this driver. The CPU would call make an > > > rtas_stop_self() call and hand over the CPU back to the resource > > > pool, > > > thereby effectively deallocating that vCPU from the LPAR. > > > NOTE: This would result in a configuration change to the LPAR > > > which is visible to the outside world. > > > > > > inactive: This cedes the vCPU to the hypervisor with a cede > > > latency > > > specifier value 2. > > > NOTE: This option does not result in a configuration change > > > and the vCPU would be still entitled to the LPAR to which it > > > earlier > > > belong to. > > > > > > Any feedback on the patchset will be immensely valuable. > > > > I still think its a layering violation... its the hypervisor manager > > that should be bothered in what state an off-lined cpu is in. > > > > From a design standpoint where we stand today is > > 1. A cede indicates that the CPU is no longer needed and can be > reassigned (remember we do dedicated CPU partitions in power) > 2. What this patch is trying to do is to say "We don't need the > CPU, but please don't reassign, put it to sleep"
FWIW, this sounds exactly like the same we have already on s390. But back then I didn't consider adding a common code infrastructure would make sense :) Besides the "online" attribute we have an additional "configure" attribute to which can only be written if the cpu is offline. Writing a "0" to it would mean that you currently won't need the cpu anymore and the hypervisor is free to reassign the cpu to a different LPAR. Writing a "1" to it means you want to use it. If there are enough resources you will get it. If not.. bad luck. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
