CIK hangs with kernel 3.15, bisected

[Grigori Goronzy]

I can confirm this fixes it for me, too.

3.15 with these fixes and the large PTE patches actually ends up being 
noticeably slower than earlier kernels with Xonotic, though. I wonder 
what's going on.

Grigori

On 12.05.2014 14:50, Christian König wrote:
> I could reproduce the problem with xonotic and I think I've found the
> issue.
>
> Please test the attached patch.
>
> Thanks,
> Christian.
>
> Am 11.05.2014 11:06, schrieb Christian König:
>>> I have tested it and it doesn't fix the hangs.
>> Yeah, thought so. Well it was just a guess.
>>
>>> (Also, I don't like the patch, because it reverts the behavior I added
>>> for userspace buffers.)
>> Actually it shouldn't affect that. The alternative domain always
>> contains GART even when userspace only specified VRAM as placement (as
>> long as it is technical possible to do so).
>>
>> So what should happen is that TTM sees the current placement, matches
>> that with the desired placement and should find that it doesn't need
>> to move the buffer (we should just test if this behavior really works
>> as expected).
>>
>> Christian.
>>
>> Am 10.05.2014 23:38, schrieb Marek Olšák:
>>> Hi Christian,
>>>
>>> I have tested it and it doesn't fix the hangs.
>>>
>>> (Also, I don't like the patch, because it reverts the behavior I added
>>> for userspace buffers.)
>>>
>>> Marek
>>>
>>>
>>>
>>> On Sat, May 10, 2014 at 6:34 PM, Christian König
>>> <deathsimple at vodafone.de> wrote:
>>>> Couldn't reproduce the issue so far. So the attached patch is just a
>>>> complete shoot into the dark found by rereading the code, but it might
>>>> actually be the problem.
>>>>
>>>> Please give it a try.
>>>>
>>>> Going to keep testing in the meantime,
>>>> Christian.
>>>>
>>>> Am 10.05.2014 10:23, schrieb Christian König:
>>>>
>>>>>> I see hangs with kernel 3.15 and SI under memory pressure, e.g. if
>>>>>> I boot
>>>>>> with radeon.vramlimit=256 and then run Xonotic timedemo with high
>>>>>> settings.
>>>>>> I haven't had a chance to bisect it yet, but it might be a similar
>>>>>> problem.
>>>>> Sounds like the same issue to me. Thx for the good test case.
>>>>>
>>>>>> Any idea what is wrong with it?
>>>>> Actually I already wondered that it went so smooth without any
>>>>> regression
>>>>> so far, didn't noticed the bug in bugzilla.kernel.org yet.
>>>>>
>>>>>> Some of the tests allocate a lot of MSAA textures and the tests also
>>>>>> run in parallel, which creates a lot of memory pressure and probably
>>>>>> causes buffer evictions.
>>>>> Sounds like the underlying problem to me. We probably evict some
>>>>> part of a
>>>>> page table without updating the page directory. Going to dig into
>>>>> it today,
>>>>> it's probably just a one liner missing somewhere in the VM code.
>>>>>
>>>>> Christian.
>>>>>
>>>>> Am 09.05.2014 23:39, schrieb Grigori Goronzy:
>>>>>> On 09.05.2014 20:03, Marek Olšák wrote:
>>>>>>>
>>>>>>> This commit which first appeared in 3.15-rc1 causes hangs on
>>>>>>> Bonaire:
>>>>>>> [...]
>>>>>>>
>>>>>>> The simplest way to reproduce the hangs is to run piglit with these
>>>>>>> parameters:
>>>>>>> -t texelFetch.fs
>>>>>>>
>>>>>>> Some of the tests allocate a lot of MSAA textures and the tests also
>>>>>>> run in parallel, which creates a lot of memory pressure and probably
>>>>>>> causes buffer evictions.
>>>>>>>
>>>>>> I see hangs with kernel 3.15 and SI under memory pressure, e.g. if
>>>>>> I boot
>>>>>> with radeon.vramlimit=256 and then run Xonotic timedemo with high
>>>>>> settings.
>>>>>> I haven't had a chance to bisect it yet, but it might be a similar
>>>>>> problem.
>>>>>>
>>>>>> Grigori
>>>>>
>>
>