Xen (and others Hypervisors) how do they handle IPIs?

2013-09-25 Thread Julian Elischer
If CPUs are mapped around, how are IPIs handled? I assume they must be emulated? I've noticed that under Xen (on both Amazon EC2 and a Redhat server) whenever you schedule a thread it always sits on the run queue for 20 uSecs before it starts running. It looks to me like it's the IPI taking

Re: Xen (and others Hypervisors) how do they handle IPIs?

2013-09-25 Thread Roger Pau Monné
On 25/09/13 16:56, Julian Elischer wrote: If CPUs are mapped around, how are IPIs handled? I assume they must be emulated? I've noticed that under Xen (on both Amazon EC2 and a Redhat server) whenever you schedule a thread it always sits on the run queue for 20 uSecs before it starts