From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Wright Subject: Re: [PATCH] kvm-vmx: add module parameter to avoid trapping HLT instructions (v2) Date: Fri, 3 Dec 2010 09:29:06 -0800 Message-ID: <20101203172906.GD10050@sequoia.sous-sol.org> References: <1291298357-5695-1-git-send-email-aliguori@us.ibm.com> <20101202191416.GQ10050@sequoia.sous-sol.org> <20101203115752.GD27994@linux.vnet.ibm.com> <20101203162731.GA11725@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Chris Wright , Anthony Liguori , kvm@vger.kernel.org, Avi Kivity , Marcelo Tosatti To: Srivatsa Vaddagiri Return-path: Received: from sous-sol.org ([216.99.217.87]:33987 "EHLO sequoia.sous-sol.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751588Ab0LCR3c (ORCPT ); Fri, 3 Dec 2010 12:29:32 -0500 Content-Disposition: inline In-Reply-To: <20101203162731.GA11725@linux.vnet.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: * Srivatsa Vaddagiri (vatsa@linux.vnet.ibm.com) wrote: > On Fri, Dec 03, 2010 at 05:27:52PM +0530, Srivatsa Vaddagiri wrote: > > On Thu, Dec 02, 2010 at 11:14:16AM -0800, Chris Wright wrote: > > > Perhaps it should be a VM level option. And then invert the notion. > > > Create one idle domain w/out hlt trap. Give that VM a vcpu per pcpu > > > (pin in place probably). And have that VM do nothing other than hlt. > > > Then it's always runnable according to scheduler, and can "consume" the > > > extra work that CFS wants to give away. > > > > That's not sufficient. Lets we have 3 guests A, B, C that need to be rate > > limited to 25% on a single cpu system. We create this idle guest D that is 100% > > cpu hog as per above definition. Now when one of the guest is idle, what ensures > > that the idle cycles of A is given only to D and not partly to B/C? > > To tackle this problem, I was thinking of having a fill-thread associated with > each vcpu (i.e both belong to same cgroup). Fill-thread consumes idle cycles > left by vcpu, but otherwise doesn't compete with it for cycles. That's what Marcelo's suggestion does w/out a fill thread.