Re: [PATCH v7 0/2] Improve VM CPUfreq and task placement behavior

[Rafael J. Wysocki]

On Sat, Oct 26, 2024 at 12:26 AM Saravana Kannan <saravanak@xxxxxxxxxx> wrote:
>
> On Tue, Oct 1, 2024 at 2:25 AM Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote:
> >
> > On 18-09-24, 17:08, David Dai wrote:
> > > Hi,
> > >
> > > This patch series is a continuation of the talk Saravana gave at LPC 2022
> > > titled "CPUfreq/sched and VM guest workload problems" [1][2][3]. The gist
> > > of the talk is that workloads running in a guest VM get terrible task
> > > placement and CPUfreq behavior when compared to running the same workload
> > > in the host. Effectively, no EAS(Energy Aware Scheduling) for threads
> > > inside VMs. This would make power and performance terrible just by running
> > > the workload in a VM even if we assume there is zero virtualization
> > > overhead.
> >
> > > David Dai (2):
> > >   dt-bindings: cpufreq: add virtual cpufreq device
> > >   cpufreq: add virtual-cpufreq driver
> > >
> > >  .../cpufreq/qemu,virtual-cpufreq.yaml         |  48 +++
> > >  drivers/cpufreq/Kconfig                       |  14 +
> > >  drivers/cpufreq/Makefile                      |   1 +
> > >  drivers/cpufreq/virtual-cpufreq.c             | 333 ++++++++++++++++++
> > >  include/linux/arch_topology.h                 |   1 +
> > >  5 files changed, 397 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/cpufreq/qemu,virtual-cpufreq.yaml
> > >  create mode 100644 drivers/cpufreq/virtual-cpufreq.c
> >
> > LGTM.
> >
> > Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
>
> Rafael/Viresh,
>
> Nudge... Any chance this will get pulled into 6.12?

This is not a fix AFAICS, so 6.12 is out of the question.

As for 6.13, Viresh thinks that this change is a good idea (or he
wouldn't have ACKed it), so it's up to him.  I'm still not convinced
that it will work on x86 or anything that doesn't use DT.

Viresh, I think that this falls into your bucket.