Re: [patch -rt 1/2] KVM: use simple waitqueue for vcpu->wq

Rik van Riel
2015-01-14T18:22:43Z

On 01/14/2015 12:12 PM, Marcelo Tosatti wrote:
> The problem:
>
> On -RT, an emulated LAPIC timer instances has the following path:
>
> 1) hard interrupt
> 2) ksoftirqd is scheduled
> 3) ksoftirqd wakes up vcpu thread
> 4) vcpu thread is scheduled
>
> This extra context switch introduces unnecessary latency in the
> LAPIC path for a KVM guest.

> This patch reduces the average latency in my tests from 14us to 11us.
>
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Acked-by: Rik van Riel <riel@redhat.com>