Long radeon stalls on recent kernels

[Michel Dänzer]

On 10.12.2014 06:39, Andy Lutomirski wrote:
> On Tue, Dec 9, 2014 at 8:06 AM, Andy Lutomirski <luto at amacapital.net> wrote:
>> On Tue, Dec 9, 2014 at 1:18 AM, Michel Dänzer <michel at daenzer.net> wrote:
>>> On 09.12.2014 09:24, Andy Lutomirski wrote:
>>>>
>>>> The relevant line from latencytop seems to be:
>>>>
>>>> 154 20441402 489139 radeon_fence_default_wait [radeon]
>>>> fence_wait_timeout ttm_bo_wait [ttm] ttm_bo_move_accel_cleanup [ttm]
>>>> radeon_move_blit.isra.12 [radeon] radeon_bo_move [radeon]
>>>> ttm_bo_handle_move_mem [ttm] ttm_bo_evict [ttm] ttm_mem_evict_first
>>>> [ttm] ttm_bo_mem_space [ttm] ttm_bo_validate [ttm]
>>>> radeon_bo_fault_reserve_notify [radeon]
>>>
>>> Which process is this?
>>
>> Xorg
>>
>>>
>>> Looks like CPU access to a BO in VRAM, but the BO is located outside of
>>> the CPU visible area of VRAM, so it has to be moved into the CPU visible
>>> area first.
>>>
>>> Which version of Mesa are you using?
>>>
>>
>> mesa-dri-drivers-10.3.3-1.20141110.fc20.x86_64
>>
>> I'm planning on upgrading to Fedora 21 fairly soon.
> 
> Upgrading to mesa-dri-drivers-10.3.3-1.20141110.fc21.x86_64 seems to
> have helped enough that my usual test (open a couple of Firefox tabs
> with graphics in them) doesn't hang anymore.

Hmm, since that looks like the exact same upstream version, maybe it was
actually upgrading something else that made the difference?


> This card still isn't *fast*.

I'm afraid it wasn't exactly a high-end card even when it was new. What
kind of operations are slow?


> Is there some way I can check that I'm actually using all 16 PCIe lanes?
> In my tinkering w/ power management settings, I got some odd logs
> suggesting that only one lane was in use.

You can try forcing off ASPM with radeon.aspm=0, other than that I'm not
sure.


> But I'm still waiting for the day that buggy userspace *can't* cause
> kernel graphics stalls.

Actually, this looks more like buggy userspace stalling itself. :)


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