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 00:18:08 +0100 Message-ID: <10291528.MoKaz8pbFD@xps13> References: <1412003903-9061-1-git-send-email-alan.carew@intel.com> <5470C514.3080307@6wind.com> <548732C9.2020201@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: dev-VfR2kkLFssw@public.gmane.org, Paolo Bonzini , qemu-devel To: Alan Carew , Pablo de Lara Return-path: In-Reply-To: <548732C9.2020201-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" 2014-12-09 18:35, Paolo Bonzini: > >>>> Did you make any progress in Qemu/KVM community? > >>>> We need to be sync'ed up with them to be sure we share the same goal. > >>>> I want also to avoid using a solution which doesn't fit with their > >>>> plan. > >>>> Remember that we already had this problem with ivshmem which was > >>>> planned to be dropped. > >>> > >>> Unfortunately, I have not yet received any feedback: > >>> http://lists.nongnu.org/archive/html/qemu-devel/2014-11/msg01103.html > >> > >> Just to add to what Alan said above, this capability does not exist in > >> qemu at the moment, and based on there having been no feedback on th > >> qemu mailing list so far, I think it's reasonable to assume that it > >> will not be implemented in the immediate future. The VM Power > >> Management feature has also been designed to allow easy migration to a > >> qemu-based solution when this is supported in future. Therefore, I'd > >> be in favour of accepting this feature into DPDK now. > >> > >> It's true that the implementation is a work-around, but there have > >> been similar cases in DPDK in the past. One recent example that comes > >> to mind is userspace vhost. The original implementation could also be > >> considered a work-around, but it met the needs of many in the > >> community. Now, with support for vhost-user in qemu 2.1, that > >> implementation is being improved. I'd see VM Power Management > >> following a similar path when this capability is supported in qemu. > > I wonder if this might be papering over a bug in the host cpufreq > driver. If the guest is not doing much and leaving a lot of idle CPU > time, the host should scale down the frequency of that CPU. In the case > of pinned VCPUs this should really "just work". What is the problem > that is being solved? > > Paolo Alan, Pablo, please could you explain your logic with VM power management? -- Thomas