From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Carew, Alan" Subject: Re: [PATCH v4 00/10] VM Power Management Date: Tue, 14 Oct 2014 12:37:51 +0000 Message-ID: <0E29434AEE0C3A4180987AB476A6F6306D28093B@IRSMSX109.ger.corp.intel.com> References: <1412003903-9061-1-git-send-email-alan.carew@intel.com> <1413142571-23069-1-git-send-email-alan.carew@intel.com> <3264386.kAdiTFhMft@xps13> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable To: "dev-VfR2kkLFssw@public.gmane.org" Return-path: In-Reply-To: <3264386.kAdiTFhMft@xps13> Content-Language: en-US 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" Hi Thomas, > -----Original Message----- > From: Thomas Monjalon [mailto:thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org] > Sent: Monday, October 13, 2014 9:26 PM > To: Carew, Alan > Cc: dev-VfR2kkLFssw@public.gmane.org > Subject: Re: [dpdk-dev] [PATCH v4 00/10] VM Power Management >=20 > Hi Alan, >=20 > 2014-10-12 20:36, Alan Carew: > > The following patches add two DPDK sample applications and an alternate > > implementation of librte_power for use in virtualized environments. > > The idea is to provide librte_power functionality from within a VM to a= ddress > > the lack of MSRs to facilitate frequency changes from within a VM. > > It is ideally suited for Haswell which provides per core frequency scal= ing. > > > > The current librte_power affects frequency changes via the acpi-cpufreq > > 'userspace' power governor, accessed via sysfs. >=20 > Something was preventing me from looking deeper in this big codebase, > but I didn't know what sounds weird. > Now I realize: the real problem is that virtualization transparency is > broken for power management. So the right thing to do is to fix it in > KVM. I think all this patchset is a huge workaround. >=20 > Did you try to fix it with Qemu/KVM? >=20 > -- > Thomas When looking at the libvirt API it would seem to be a natural fit to have p= ower management sitting there, so in essence I would agree. However with a DPDK solution it would be possible to re-use the message bus= to pass information like device stats, application state, D-state requests= etc. to the host and allow for management layer(e.g. OpenStack) to make in= formed decisions. Also, the scope of adding power management to qemu/KVM would be huge; while= the easier path is not always the best and the problem of power management= in VMs is both a DPDK problem (given that librte_power only worked on the = host) and a general virtualization problem that would be better solved by t= hose with direct knowledge of Qemu/KVM architecture and influence on the di= rection of the Qemu project. As it stands, the host backend is simply an example application that can be= replaced by a VMM or Orchestration layer, by using Virtio-Serial it has ob= vious leanings to Qemu, but even this could be easily swapped out for XenBu= s, IVSHMEM, IP etc. If power management is to be eventually supported by Hypervisors directly t= hen we could also enable to option to switch to that environment, currently= the librte_power implementations (VM or Host) can be selected dynamically(= environment auto-detection) or explicitly via rte_power_set_env(), adding a= n arbitrary number of environments is relatively easy. I hope this helps to clarify the approach. Thanks, Alan.