Why is Thunderbolt 3 limited to 2.5 GT/s on Linux?

[Marek Olšák]

On Fri, Jul 5, 2019 at 5:27 AM Timur Kristóf <timur.kristof at gmail.com>
wrote:

> On Wed, 2019-07-03 at 14:44 -0400, Marek Olšák wrote:
> > You can run:
> > AMD_DEBUG=testdmaperf glxgears
> >
> > It tests transfer sizes of up to 128 MB, and it tests ~60 slightly
> > different methods of transfering data.
> >
> > Marek
>
>
> Thanks Marek, I didn't know about that option.
> Tried it, here is the output: https://pastebin.com/raw/9SAAbbAA
>
> I'm not quite sure how to interpret the numbers, they are inconsistent
> with the results from both pcie_bw and amdgpu.benchmark, for example
> GTT->VRAM at a 128 KB is around 1400 MB/s (I assume that is megabytes /
> sec, right?).
>

Based on the SDMA results, you have 2.4 GB/s. For 128KB, it's 2.2 GB/s for
GTT->VRAM copies.

Marek
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