Re: DRAM power consumption with turbostat

Julia Lawall
2022-02-06T08:35:36Z

On Sun, 6 Feb 2022, Zhang Rui wrote:

> Hi, Julia,
>
> Thanks for reporting this.
>
> On Sun, 2022-01-30 at 11:27 +0100, Julia Lawall wrote:
> > Hello,
> >
> > I was wondering whether the DRAM power consumption reported by
> > turbostat
> > is reliable on recent Intel machines?
> >
> > In particular, I observed that turbostat reported a high DRAM energy
> > comsumption on a machine (Intel 5128)
>
> are you sure it is 5128? google tells me that 5128 is pretty old, in
> around 2006.

Oops! 5218

Thanks for the pointer to the new version. I will try that.

julia

>
> can you please paste the lscpu output?
>
> > with persistent memory, but where
> > the persistent memory was not being used. A colleague did an
> > experiemnt
> > on another machine with persistent memory, and reported:
> >
> > -----
> >
> > I didn't run the test on troll but on another server equipped with PM
> > where I was able to reproduce the bug and by reading directly the msr
> > registers, I see that:
> > CPU Energy units = 0.00006104J
> > DRAM Energy units = 0.00001526J
> >
> > However turbostat assumes that the DRAM Energy units is 0.00006104J
> > when
> > it runs the computation to obtain Joules (hence the too-high value
> > returned by turbostat)
>
> And can you please try latest version of turbostat?
>
> The problem should be fixed by the below commit
>
> commit abdc75ab53b7fd2ef42c79e88cf0caf2d007c4f2
> Author: Zhang Rui <rui.zhang@intel.com>
> AuthorDate: Thu Mar 11 10:05:13 2021 +0800
> Commit: Len Brown <len.brown@intel.com>
> CommitDate: Tue May 4 18:23:14 2021 -0400
>
> tools/power turbostat: Fix DRAM Energy Unit on SKX
>
> SKX uses fixed DRAM Energy Unit, just like HSX and BDX.
>
> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
> Signed-off-by: Len Brown <len.brown@intel.com>
>
> thanks,
> rui
> >
> > -----
> >
> > I see the code in turbostat that just uses the CPU energy units value
> > (rapl_dram_energy_units_probe), but I don't know what was the MSR
> > used to
> > collect the above information. Overall, I am wondering if the DRAM
> > energy
> > consumption values are reliable in cases with and without persistent
> > memory.
> >
> > thanks,
> > julia
>
>