Re: [RFC PATCH 0/2] Mitigating Excessive Pause-Loop Exiting in VM-Agnostic KVM

From: Wanpeng Li
Date: Sun Apr 25 2021 - 23:58:36 EST

On Mon, 26 Apr 2021 at 11:19, Kenta Ishiguro
<kentaishiguro@xxxxxxxxxxxxxxxxxxxx> wrote:
> Thank you for the reply.
> My question is about following scenario:
> 1. running vCPU receives IPI and the vCPU's ipi_received gets true
> 2. the vCPU responds to the IPI
> 3. the vCPU exits
> 4. the vCPU is preempted by KVM
> 5. the vCPU is boosted, but it has already responded to the IPI
> 6. the vCPU enters and the vCPU's ipi_received is cleaned
> In this case, I think the check of vcpu->preempted does not limit the candidate vCPUs.

Good point, you are right. However, actually I played with that code a
bit before, I have another version adding the vcpu->preempted checking
when marking IPI receiver, the score is not as good as expected.