From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40777) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XzRYK-000055-P1 for qemu-devel@nongnu.org; Fri, 12 Dec 2014 09:50:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XzRYE-00058O-EX for qemu-devel@nongnu.org; Fri, 12 Dec 2014 09:50:44 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36975) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XzRYD-00057z-Qy for qemu-devel@nongnu.org; Fri, 12 Dec 2014 09:50:37 -0500 Message-ID: <548B00B3.8040201@redhat.com> Date: Fri, 12 Dec 2014 15:50:27 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <1412003903-9061-1-git-send-email-alan.carew@intel.com> <5470C514.3080307@6wind.com> <548732C9.2020201@redhat.com> <10291528.MoKaz8pbFD@xps13> <0E29434AEE0C3A4180987AB476A6F6306D2B6443@IRSMSX109.ger.corp.intel.com> In-Reply-To: <0E29434AEE0C3A4180987AB476A6F6306D2B6443@IRSMSX109.ger.corp.intel.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [dpdk-dev] [PATCH v4 00/10] VM Power Management List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Carew, Alan" , Thomas Monjalon , "De Lara Guarch, Pablo" Cc: "dev@dpdk.org" , qemu-devel On 12/12/2014 14:00, Carew, Alan wrote: > The problem is deterministic control of host CPU frequency and the DPDK usage > model. > A hands-off power governor will scale based on workload, whether this is a host > application or VM, so no problems or bug there. > > Where this solution fits is where an application wants to control its own > power policy, for example l3fwd_power uses librte_power library to change > frequency via apci_cpufreq based on application heuristics rather than > relying on an inbuilt policy for example ondemand or performance. > > This ability has existed in DPDK for host usage for some time and VM power > management allows this use case to be extended to cater for virtual machines > by re-using the librte_power interface to encapsulate the VM->Host > comms and provide an example means of managing such communications. > > I hope this clears it up a bit. Ok, this looks specific enough that an out-of-band solution within DPDK sounds like the best approach. It seems unnecessary to involve the hypervisor (neither KVM nor QEMU). Paolo