Long radeon stalls on recent kernels

[Michel Dänzer]

On 19.11.2014 09:21, Andy Lutomirski wrote:
> On Mon, Nov 17, 2014 at 1:51 AM, Michel Dänzer <michel at daenzer.net> wrote:
>> On 15.11.2014 07:21, Andy Lutomirski wrote:
>>>
>>> On recent kernels (3.16 through 3.18-rc4, perhaps), doing anything
>>> graphics intensive seems to cause my system to become unusable for
>>> tens of seconds.  Pointing Firefox at Google Maps is a big offender --
>>> it can take several minutes for me to move my mouse far enough to
>>> close the tab and get my computer back.
>>>
>>> On bootup, I get this warning:
>>> [drm:btc_dpm_set_power_state] *ERROR*
>>> rv770_restrict_performance_levels_before_switch failed
>>>
>>> Setting radeon.dpm=0 seems to work around this problem at the cost of
>>> giving my rather slow graphics.
>>>
>>> Are there known issues here?
>>
>>
>> Can you bisect the kernel, or at least isolate which kernel version first
>> introduced the problem?
>
> With whatever userspace I'm running, I'm seeing it 3.13, 3.14, 3.15,
> 3.16, and 3.18-rc4+.  I haven't tried other versions.
>
> With radeon.dpm=0, I can still trigger short stalls (around one
> second), but I seem unable to trigger long stalls easily.  (I say
> easily because, just as I was typing this email, my system stalled for
> about a minute.)

I can only think of two things offhand that could cause such extremely 
long stalls: Swap thrashing or IRQ storms.

With a setup where you can easily trigger long stalls, can you try 
getting a CPU profile for a stall with sysprof or perf?


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