Re: [RFC][PATCH 0/4] arm64:kvm: teach guest sched that VCPUs can be preempted

[Sergey Senozhatsky]

On (20/07/21 13:17), Sergey Senozhatsky wrote:
> Hello,
> 
> 	RFC
> 
> 	We noticed that in a number of cases when we wake_up_process()
> on arm64 guest we end up enqueuing that task on a preempted VCPU. The culprit
> appears to be the fact that arm64 guests are not aware of VCPU preemption
> as such, so when sched picks up an idle VCPU it always assumes that VCPU
> is available:
> 
>       wake_up_process()
>        try_to_wake_up()
>         select_task_rq_fair()
>          available_idle_cpu()
>           vcpu_is_preempted()    // return false;
> 
> Which is, obviously, not the case.
> 
> This RFC patch set adds a simple vcpu_is_preempted() implementation so
> that scheduler can make better decisions when it search for the idle
> (v)CPU.

Hi,

A gentle ping.

	-ss