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

[Saravana Kannan]

On Mon, Oct 28, 2024 at 4:39 AM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
>
> 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.

IIUC, we sent this patch before the 6.12 merge window closed. That's
why I was checking if we can get this into 6.12 :) And this is a new
driver, so the chances of this breaking anything in 6.12 is close to
zero.

> Viresh, I think that this falls into your bucket.

Anyway, 6.13 is fine, but would appreciate 6.12 (so we get it into LTS).

Thanks,
Saravana