Re: AMD Pstate

Huang Rui
2021-11-23T11:33:12Z

On Tue, Nov 23, 2021 at 07:22:24PM +0800, Mike Lothian wrote:
> On Tue, 23 Nov 2021 at 11:18, Huang Rui <ray.huang@amd.com> wrote:
> >
> > On Tue, Nov 23, 2021 at 06:47:34PM +0800, Mike Lothian wrote:
> > > Hi again
> > >
> > > Do I need to enable something else for shedutil to work, I've tried
> > > with and without shared_mem? Compiling a kernel with -j16 has the freq
> > > stuck at 1GHz on all cores - ondemand works fine
> > >
> >
> > If you set the CONFIG_CPU_FREQ_GOV_SCHEDUTIL, then no more configurations.
> >
> > Did you use the V4 version?
> >
> > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.kernel.org%2Fpub%2Fscm%2Flinux%2Fkernel%2Fgit%2Frui%2Flinux.git%2Flog%2F%3Fh%3Damd-pstate-dev-v4&amp;data=04%7C01%7Cray.huang%40amd.com%7C3006dbf33ae54ffaa1aa08d9ae738d2d%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637732633874328299%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=L1H7yy9UCweIH9CaSYTrfo4DZUDok1wgQxjtNCNLC9g%3D&amp;reserved=0
> >
> > > That's on a AMD Ryzen 9 5900HX
> > >
> > > Also compiling with Clang-13 gives the following warnings:
> > >
> > > drivers/cpufreq/amd-pstate.c:257:6: warning: variable 'amd_des_perf'
> > > is used uninitialized whenever 'if' condition is false
> > > [-Wsometimes-uninitialized]
> > >
> > > if (target_perf < capacity)
> > >
> > > ^~~~~~~~~~~~~~~~~~~~~~
> > >
> > > drivers/cpufreq/amd-pstate.c:272:40: note: uninitialized use occurs here
> > >
> > > amd_des_perf = clamp_t(unsigned long, amd_des_perf,
> > >
> > > ^~~~~~~~~~~~
> >
> > Ah, miss one line. Thanks for the info. I will correct it.
> >
> > Thanks,
> > Ray
> >
>
> Hi
>
> Yes I used v4 and CONFIG_CPU_FREQ_GOV_SCHEDUTIL was set as the
> default, is there any other info that would be useful, I can switch
> back to schedutil from ondemand and collect for you
>

> > > That's on a AMD Ryzen 9 5900HX

May I know the CPU family/model id? (you can dump it from lscpu)

But you may need to add "amd_pstate.shared_mem=1" in your grub to enable
the shared memory manually. Because we are debugging the performance issue
on shared memory solution, so it is disabled by default.

> > > amd_des_perf = clamp_t(unsigned long, amd_des_perf,

It's not the V4's codes. I renamed this variate in the V4.

Thanks,
Ray