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

[Michel Dänzer]

On 2019-06-28 2:21 p.m., Timur Kristóf wrote:
> 
> I haven't found a good way to measure the maximum PCIe throughput
> between the CPU and GPU,

amdgpu.benchmark=3

on the kernel command line will measure throughput for various transfer
sizes during driver initialization.


> but I did take a look at AMD's sysfs interface at
> /sys/class/drm/card1/device/pcie_bw which while running the bottlenecked
> game. The highest throughput I saw there was only 2.43 Gbit /sec.

PCIe bandwidth generally isn't a bottleneck for games, since they don't
constantly transfer large data volumes across PCIe, but store them in
the GPU's local VRAM, which is connected at much higher bandwidth.


-- 
Earthling Michel Dänzer               |              https://www.amd.com
Libre software enthusiast             |             Mesa and X developer