Re: [PATCH] KVM: Disable wake-affine vCPU process to mitigate lock holder preemption

[Dario Faggioli]

On Tue, 2019-07-30 at 17:33 +0800, Wanpeng Li wrote:
> However, in multiple VMs over-subscribe virtualization scenario, it
> increases 
> the probability to incur vCPU stacking which means that the sibling
> vCPUs from 
> the same VM will be stacked on one pCPU. I test three 80 vCPUs VMs
> running on 
> one 80 pCPUs Skylake server(PLE is supported), the ebizzy score can
> increase 17% 
> after disabling wake-affine for vCPU process. 
> 
Can't we achieve this by removing SD_WAKE_AFFINE from the relevant
scheduling domains? By acting on
/proc/sys/kernel/sched_domain/cpuX/domainY/flags, I mean?

Of course this will impact all tasks, not only KVM vcpus. But if the
host does KVM only anyway...

Regards
-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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