On 04/04/2018 15:23, Eero Tamminen wrote:

On 04.04.2018 15:42, Tvrtko Ursulin wrote:
On 04/04/2018 13:15, Eero Tamminen wrote:
I've now tested v5 with old Ubuntu kernel on KBL, and with latest
drm-tip kernel on SNB, HSW, BYT, BSW and BDW GT & GT3.

Generic test results

* Tool works on all of them

* The new error messages and headings look good

* Idle IMC read amounts correspond to expected values on SNB & HSW.
   The much smaller values on BDW & SKL are due to FBC (how well
   it compresses, naturally depends on screen content).

Unlike I assumed earlier, it's not actually uncore bandwidth.
It's RAM bandwidth, I guess the IMC abbreviation is for something
like Intel/Integrated Memory Controller.

Note that it includes also any memory bandwidth used by CPU, and if
the data fits into LLC, it doesn't show it.

However, knowing whether CPU uses memory bandwidth is actually useful
thing because RAM bandwidth is a shared resource with GPU.  One can
check other tasks bandwidth usage before launching the GPU task.

Hm OK, you managed to explain it. Because in the meantime I have observed one oddity with write bandwidth on my headless SkullCanyon NUC. It idles around 28MiB/s,

On idle machine, write bandwidth usage should be zero.

What is causing the writes?

It was probably caused by some of the kernel debug options I had set. Or maybe disabled dynticks. With fewer debug options and dynticks I cannot reproduce that any more.


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