From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH] kvm-vmx: add module parameter to avoid trapping HLT instructions (v2) Date: Thu, 02 Dec 2010 16:37:58 -0600 Message-ID: <4CF81FC6.7090503@codemonkey.ws> References: <1291298357-5695-1-git-send-email-aliguori@us.ibm.com> <20101202191416.GQ10050@sequoia.sous-sol.org> <20101202204016.GB31316@amt.cnet> <20101202210737.GS10050@sequoia.sous-sol.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm@vger.kernel.org, Avi Kivity , Srivatsa Vaddagiri To: Chris Wright Return-path: Received: from mail-qw0-f46.google.com ([209.85.216.46]:62447 "EHLO mail-qw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753566Ab0LBWiD (ORCPT ); Thu, 2 Dec 2010 17:38:03 -0500 Received: by qwb7 with SMTP id 7so8911094qwb.19 for ; Thu, 02 Dec 2010 14:38:02 -0800 (PST) In-Reply-To: <20101202210737.GS10050@sequoia.sous-sol.org> Sender: kvm-owner@vger.kernel.org List-ID: On 12/02/2010 03:07 PM, Chris Wright wrote: >> But you agree this is no KVM business. >> > Like non-trapping hlt, that too will guarantee that the guest is preempted > by timeslice exhaustion (and is simpler than non-trapping hlt). So it > may well be the simplest for the case where we are perfectly committed > (i.e. the vcpu fractional core count totals the pcpu count). But once > we are undercommitted we still need some extra logic to handle the hard > cap and something to kick the running guest off the cpu and suck up the > extra cycles in a power conserving way. > I'm not entirely sure TBH. If you think of a cloud's per-VCPU capacity in terms of Compute Units, having a model where a VCPU maps to 1-3 units depending on total load is potentially interesting particularly if the VCPU's capacity only changes in discrete amounts, that the expected capacity is communicated to the guest, and that the capacity only changes periodically. Regards, Anthony Liguori > thanks, > -chris > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >