From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Monjalon Subject: Re: [PATCH v4 00/10] VM Power Management Date: Fri, 12 Dec 2014 17:10:08 +0100 Message-ID: <6597811.ARdDfzU0XI@xps13> References: <1412003903-9061-1-git-send-email-alan.carew@intel.com> <0E29434AEE0C3A4180987AB476A6F6306D2B6443@IRSMSX109.ger.corp.intel.com> <548B00B3.8040201@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: dev-VfR2kkLFssw@public.gmane.org, qemu-devel-qX2TKyscuCcdnm+yROfE0A@public.gmane.org To: Paolo Bonzini Return-path: In-Reply-To: <548B00B3.8040201-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" 2014-12-12 15:50, Paolo Bonzini: > 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, I don't understand why you don't imagine controlling frequency scaling of a pinned vCPU transparently? In my understanding, we currently cannot control frequency scaling without knowing wether we are in a VM or not. -- Thomas From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33231) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XzSnj-0007MG-GA for qemu-devel@nongnu.org; Fri, 12 Dec 2014 11:10:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XzSnb-0007RP-VR for qemu-devel@nongnu.org; Fri, 12 Dec 2014 11:10:43 -0500 Received: from mail-wi0-f180.google.com ([209.85.212.180]:37483) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XzSnb-0007RG-9L for qemu-devel@nongnu.org; Fri, 12 Dec 2014 11:10:35 -0500 Received: by mail-wi0-f180.google.com with SMTP id n3so3059692wiv.7 for ; Fri, 12 Dec 2014 08:10:34 -0800 (PST) From: Thomas Monjalon Date: Fri, 12 Dec 2014 17:10:08 +0100 Message-ID: <6597811.ARdDfzU0XI@xps13> In-Reply-To: <548B00B3.8040201@redhat.com> References: <1412003903-9061-1-git-send-email-alan.carew@intel.com> <0E29434AEE0C3A4180987AB476A6F6306D2B6443@IRSMSX109.ger.corp.intel.com> <548B00B3.8040201@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" 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: Paolo Bonzini Cc: "De Lara Guarch, Pablo" , dev@dpdk.org, "Carew, Alan" , qemu-devel@nongnu.org 2014-12-12 15:50, Paolo Bonzini: > 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, I don't understand why you don't imagine controlling frequency scaling of a pinned vCPU transparently? In my understanding, we currently cannot control frequency scaling without knowing wether we are in a VM or not. -- Thomas