Re: DRAM power consumption with turbostat

[Zhang Rui <rui.zhang@intel.com>]

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.

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