[PATCH] Revert "drm/radeon: Try evicting from CPU accessible to inaccessible VRAM first"

[Michel Dänzer]

On 23/03/17 06:26 PM, Julien Isorce wrote:
> Hi Michel,
> 
> When it happens, the main thread of our gl based app is stuck on a
> ioctl(RADEON_CS). I set RADEON_THREAD=false to ease the debugging but
> same thing happens if true. Other threads are only si_shader:0,1,2,3 and
> are doing nothing, just waiting for jobs. I can also do sudo gdb -p
> $(pidof Xorg) to block the X11 server, to make sure there is no ping
> pong between 2 processes. All other processes are not loading
> dri/radeonsi_dri.so . And adding a few traces shows that the above ioctl
> call is looping for ever on
> https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/ttm/ttm_bo.c#L819
> <https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/ttm/ttm_bo.c#L819> and
> comes from
> mesa https://cgit.freedesktop.org/mesa/mesa/tree/src/gallium/winsys/radeon/drm/radeon_drm_cs.c#n454
> . 
> 
> After adding even more traces I can see that the bo, which is being
> indefinitely evicted, has the flag RADEON_GEM_NO_CPU_ACCESS.
> And it gets 3 potential placements after calling "radeon_evict_flags". 
>  1: VRAM cpu inaccessible, fpfn is 65536
>  2: VRAM cpu accessible, fpfn is 0
>  3: GTT, fpfn is 0
> 
> And it looks like it continuously succeeds to move on the second
> placement. So I might be wrong but it looks it is not even a ping pong
> between VRAM accessible / not accessible, it just keeps being blited in
> the CPU accessible part of the VRAM.

Thanks for the detailed description! AFAICT this can only happen due to
a silly mistake I made in this code. Does this fix it?

diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c
index 5c7cf644ba1d..37d68cd1f272 100644
--- a/drivers/gpu/drm/radeon/radeon_ttm.c
+++ b/drivers/gpu/drm/radeon/radeon_ttm.c
@@ -213,8 +213,8 @@ static void radeon_evict_flags(struct ttm_buffer_object *bo,
                        rbo->placement.num_busy_placement = 0;
                        for (i = 0; i < rbo->placement.num_placement; i++) {
                                if (rbo->placements[i].flags & TTM_PL_FLAG_VRAM) {
-                                       if (rbo->placements[0].fpfn < fpfn)
-                                               rbo->placements[0].fpfn = fpfn;
+                                       if (rbo->placements[i].fpfn < fpfn)
+                                               rbo->placements[i].fpfn = fpfn;
                                } else {
                                        rbo->placement.busy_placement =
                                                &rbo->placements[i];



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