Re: [RFC -v3 PATCH 0/3] directed yield for Pause Loop Exiting

From: Mike Galbraith
Date: Tue Jan 04 2011 - 01:42:32 EST

A couple questions.

On Mon, 2011-01-03 at 16:26 -0500, Rik van Riel wrote:
> When running SMP virtual machines, it is possible for one VCPU to be
> spinning on a spinlock, while the VCPU that holds the spinlock is not
> currently running, because the host scheduler preempted it to run
> something else.

Do you have any numbers?

If I were to, say, run a 256 CPU VM on my quad, would this help me get
more hackbench or whatever oomph from my (256X80386/20:) box?

> Both Intel and AMD CPUs have a feature that detects when a virtual
> CPU is spinning on a lock and will trap to the host.

Does an Intel Q6600 have this trap gizmo (iow will this do anything at
all for my little box if I were to try it out).


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