lol youre quick! "Windows has supported peer to peer DMA for years so it already has a numbers of optimizations that are only now becoming possible on Linux"
whoa, i figured linux would be ahead of windows when it comes to things like that. but peer-to-peer dma is something that is only recently possible on linux, but has been possible on windows? what changed recently that allows for peer to peer dma in linux? also, in the context of a game running opengl on some gpu, is the "peer-to-peer" dma transfer something like: the game draw's to some memory it has allocated, then a DMA transfer gets that and moves it into the graphics card output? also, i know it can be super annoying trying to debug an issue like this, with someone like me who has all types of differences from a normal setup (e.g. using it via egpu, using a kernel with custom configs and stuff) so as a token of my appreciation i donated 50$ to the red cross' corona virus outbreak charity thing, on behalf of amd-gfx. On Tue, May 19, 2020 at 4:13 PM Alex Deucher <alexdeuc...@gmail.com> wrote: > > On Tue, May 19, 2020 at 3:44 PM Javad Karabi <karabija...@gmail.com> wrote: > > > > just a couple more questions: > > > > - based on what you are aware of, the technical details such as > > "shared buffers go through system memory", and all that, do you see > > any issues that might exist that i might be missing in my setup? i > > cant imagine this being the case because the card works great in > > windows, unless the windows driver does something different? > > > > Windows has supported peer to peer DMA for years so it already has a > numbers of optimizations that are only now becoming possible on Linux. > > > - as far as kernel config, is there anything in particular which > > _should_ or _should not_ be enabled/disabled? > > You'll need the GPU drivers for your devices and dma-buf support. > > > > > - does the vendor matter? for instance, this is an xfx card. when it > > comes to different vendors, are there interface changes that might > > make one vendor work better for linux than another? i dont really > > understand the differences in vendors, but i imagine that the vbios > > differs between vendors, and as such, the linux compatibility would > > maybe change? > > board vendor shouldn't matter. > > > > > - is the pcie bandwidth possible an issue? the pcie_bw file changes > > between values like this: > > 18446683600662707640 18446744071581623085 128 > > and sometimes i see this: > > 4096 0 128 > > as you can see, the second value seems significantly lower. is that > > possibly an issue? possibly due to aspm? > > pcie_bw is not implemented for navi yet so you are just seeing > uninitialized data. This patch set should clear that up. > https://patchwork.freedesktop.org/patch/366262/ > > Alex > > > > > On Tue, May 19, 2020 at 2:20 PM Javad Karabi <karabija...@gmail.com> wrote: > > > > > > im using Driver "amdgpu" in my xorg conf > > > > > > how does one verify which gpu is the primary? im assuming my intel > > > card is the primary, since i have not done anything to change that. > > > > > > also, if all shared buffers have to go through system memory, then > > > that means an eGPU amdgpu wont work very well in general right? > > > because going through system memory for the egpu means going over the > > > thunderbolt connection > > > > > > and what are the shared buffers youre referring to? for example, if an > > > application is drawing to a buffer, is that an example of a shared > > > buffer that has to go through system memory? if so, thats fine, right? > > > because the application's memory is in system memory, so that copy > > > wouldnt be an issue. > > > > > > in general, do you think the "copy buffer across system memory might > > > be a hindrance for thunderbolt? im trying to figure out which > > > directions to go to debug and im totally lost, so maybe i can do some > > > testing that direction? > > > > > > and for what its worth, when i turn the display "off" via the gnome > > > display settings, its the same issue as when the laptop lid is closed, > > > so unless the motherboard reads the "closed lid" the same as "display > > > off", then im not sure if its thermal issues. > > > > > > On Tue, May 19, 2020 at 2:14 PM Alex Deucher <alexdeuc...@gmail.com> > > > wrote: > > > > > > > > On Tue, May 19, 2020 at 2:59 PM Javad Karabi <karabija...@gmail.com> > > > > wrote: > > > > > > > > > > given this setup: > > > > > laptop -thunderbolt-> razer core x -> xfx rx 5600 xt raw 2 -hdmi-> > > > > > monitor > > > > > DRI_PRIME=1 glxgears gears gives me ~300fps > > > > > > > > > > given this setup: > > > > > laptop -thunderbolt-> razer core x -> xfx rx 5600 xt raw 2 > > > > > laptop -hdmi-> monitor > > > > > > > > > > glx gears gives me ~1800fps > > > > > > > > > > this doesnt make sense to me because i thought that having the monitor > > > > > plugged directly into the card should give best performance. > > > > > > > > > > > > > Do you have displays connected to both GPUs? If you are using X which > > > > ddx are you using? xf86-video-modesetting or xf86-video-amdgpu? > > > > IIRC, xf86-video-amdgpu has some optimizations for prime which are not > > > > yet in xf86-video-modesetting. Which GPU is set up as the primary? > > > > Note that the GPU which does the rendering is not necessarily the one > > > > that the displays are attached to. The render GPU renders to it's > > > > render buffer and then that data may end up being copied other GPUs > > > > for display. Also, at this point, all shared buffers have to go > > > > through system memory (this will be changing eventually now that we > > > > support device memory via dma-buf), so there is often an extra copy > > > > involved. > > > > > > > > > theres another really weird issue... > > > > > > > > > > given setup 1, where the monitor is plugged in to the card: > > > > > when i close the laptop lid, my monitor is "active" and whatnot, and i > > > > > can "use it" in a sense > > > > > > > > > > however, heres the weirdness: > > > > > the mouse cursor will move along the monitor perfectly smooth and > > > > > fine, but all the other updates to the screen are delayed by about 2 > > > > > or 3 seconds. > > > > > that is to say, its as if the laptop is doing everything (e.g. if i > > > > > open a terminal, the terminal will open, but it will take 2 seconds > > > > > for me to see it) > > > > > > > > > > its almost as if all the frames and everything are being drawn, and > > > > > the laptop is running fine and everything, but i simply just dont get > > > > > to see it on the monitor, except for one time every 2 seconds. > > > > > > > > > > its hard to articulate, because its so bizarre. its not like, a "low > > > > > fps" per se, because the cursor is totally smooth. but its that > > > > > _everything else_ is only updated once every couple seconds. > > > > > > > > This might also be related to which GPU is the primary. It still may > > > > be the integrated GPU since that is what is attached to the laptop > > > > panel. Also the platform and some drivers may do certain things when > > > > the lid is closed. E.g., for thermal reasons, the integrated GPU or > > > > CPU may have a more limited TDP because the laptop cannot cool as > > > > efficiently. > > > > > > > > Alex _______________________________________________ amd-gfx mailing list amd-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/amd-gfx
