Re: [RFC PATCH v1 0/2] Avoid rcu_core() if CPU just left guest vcpu
From: Leonardo Bras
Date: Fri May 10 2024 - 22:09:05 EST
On Wed, May 08, 2024 at 07:01:29AM -0700, Sean Christopherson wrote:
> On Wed, May 08, 2024, Leonardo Bras wrote:
> > Something just hit me, and maybe I need to propose something more generic.
>
> Yes. This is what I was trying to get across with my complaints about keying off
> of the last VM-Exit time. It's effectively a broad stroke "this task will likely
> be quiescent soon" and so the core concept/functionality belongs in common code,
> not KVM.
>
Hello Sean,
Paul implemented the RCU patience cmdline option, that will help avoiding
rcuc waking up if the grace period is younger than X miliseconds, which
means the last quiescent state needs to be at least X miliseconds old.
With that I just have to add a quiescent state in guest_exit(), and we will
be able to get the same effect of last_guest_exit patch.
I sent this RFC patch doing that:
https://lore.kernel.org/all/20240511020557.1198200-1-leobras@xxxxxxxxxx/
Please take a look.
Thanks!
Leo