On Sun, Jun 30, 2019 at 2:27 PM Timur Kristóf <timur.kristof@xxxxxxxxx> wrote: > > > > > Sure, though in this case 3 of those downstream ports are not > > > exposed > > > by the hardware, so it's a bit surprising to see them there. > > > > They lead to other peripherals on the TBT host router such as the TBT > > controller and xHCI. Also there are two downstream ports for > > extension > > from which you eGPU is using one. > > If you look at the device tree from my first email, you can see that > both the GPU and the XHCI uses the same port: 04:04.0 - in fact I can > even remove the other 3 ports from the system without any consequences. > > > > Like I said the device really is limited to 2.5 GT/s even though it > > > should be able to do 8 GT/s. > > > > There is Thunderbolt link between the host router (your host system) > > and > > the eGPU box. That link is not limited to 2.5 GT/s so even if the > > slot > > claims it is PCI gen1 the actual bandwidth can be much higher because > > of > > the virtual link. > > Not sure I understand correctly, are you saying that TB3 can do 40 > Gbit/sec even though the kernel thinks it can only do 8 Gbit / sec? > > I haven't found a good way to measure the maximum PCIe throughput > between the CPU and GPU, 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. > > One more thought. I've also looked at > /sys/class/drm/card1/device/pp_dpm_pcie - which tells me that amdgpu > thinks it is running on a 2.5GT/s x8 link (as opposed to the expected 8 > GT/s x4). Can this be a problem? We limit the speed of the link the the driver to the max speed of any upstream links. So if there are any links upstream limited to 2.5 GT/s, it doesn't make sense to clock the local link up to faster speeds. Alex > > > > > > > > 3. Is it possible to manually set them to 8 GT/s? > > > > > > > > No idea. > > > > > > > > Are you actually seeing some performance issue because of this or > > > > are > > > > you just curious? > > > > > > Yes, I see a noticable performance hit: some games have very low > > > frame > > > rate while neither the CPU nor the GPU are fully utilized. > > > > Is that problem in Linux only or do you see the same issue in Windows > > as > > well? > > > I admit I don't have Windows on this computer now and it has been some > time since I last tried it, but when I did, I didn't see this problem. > > Best regards, > Tim > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
