On 2019-07-01 6:01 p.m., Timur Kristóf wrote: > On Mon, 2019-07-01 at 16:54 +0200, Michel Dänzer wrote: >> 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. > > Thanks, I will definitely try that. > Is this the only way to do this, or is there a way to benchmark it > after it already booted? The former. At least in theory, it's possible to unload the amdgpu module while nothing is using it, then load it again. >>> 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. > > There are reasons why I think the problem is the bandwidth: > 1. The same issues don't happen when the GPU is not used with a TB3 > enclosure. > 2. In case of radeonsi, the problem was mitigated once Marek's SDMA > patch was merged, which hugely reduces the PCIe bandwidth use. > 3. In less optimized cases (for example D9VK), the problem is still > very noticable. However, since you saw as much as ~20 Gbit/s under different circumstances, the 2.43 Gbit/s used by this game clearly isn't a hard limit; there must be other limiting factors. -- Earthling Michel Dänzer | https://www.amd.com Libre software enthusiast | Mesa and X developer _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
