From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Galbraith <efault@gmx.de>
Subject: Re: [RFC -v3 PATCH 0/3] directed yield for Pause Loop Exiting
Date: Tue, 04 Jan 2011 07:42:15 +0100
Message-ID: <1294123335.11283.26.camel@marge.simson.net>
References: <20110103162637.29f23c40@annuminas.surriel.com>
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Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Avi Kiviti <avi@redhat.com>,
	Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Chris Wright <chrisw@sous-sol.org>
To: Rik van Riel <riel@redhat.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
In-Reply-To: <20110103162637.29f23c40@annuminas.surriel.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

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).

	-Mike