https://bugs.freedesktop.org/show_bug.cgi?id=84662
Bug ID: 84662 Summary: Long pauses with Unreal demo Elemental on R9270X since : Always flush the HDP cache before submitting a CS to the GPU Product: Mesa Version: git Hardware: Other OS: All Status: NEW Severity: normal Priority: medium Component: Drivers/Gallium/radeonsi Assignee: dri-devel@lists.freedesktop.org Reporter: adf.lists@gmail.com
R9270X PCIE 2.0 2 gig vram 4 gig ram.
Unreal demo Elemental only recently started working with git llvm/mesa, do no bisection done on these.
The demo even when working is very broken - constant 1/4 sec stutters with a couple of 1/2 - 1 sec.
But after -
commit 4439d469706699b4e69ef410ebc9115339f6e9e6 Author: Michel Dänzer michel.daenzer@amd.com Date: Thu Jul 31 18:43:49 2014 +0900
drm/radeon: Always flush the HDP cache before submitting a CS to the GPU
This ensures the GPU sees all previous CPU writes to VRAM, which makes it safe:
* For userspace to stream data from CPU to GPU via VRAM instead of GTT * For IBs to be stored in VRAM instead of GTT * For ring buffers to be stored in VRAM instead of GTT, if the HPD flush is performed via MMIO
There are far longer pauses of many seconds - run time to unreal logo on "good" is 3:45 on bad best 5:39 can be longer.
Screens to be attached show quite different vram/gtt usage between good and bad.
Related to
https://bugs.freedesktop.org/show_bug.cgi?id=82050
I bisected to the same commit in that bug, but applying the mesa patch
https://bugs.freedesktop.org/show_bug.cgi?id=82050#c19
doesn't help here.
CONFIG_CMA is not set.
Tried kernel org 3.17-rc7 as it was reported in above as working, but not for me.