CIK hangs with kernel 3.15, bisected

[Marek Olšák]

Your latest patches fix the regression.

The performance regression can also be reproduced with piglit "-t
texelFetch.fs".

Kernel 3.14:
   real    0m17.724s
   user    0m41.905s
   sys    0m11.299s

The problematic commit checked out + your fixes (without the PTE patch I think):
   real    0m23.474s
   user    1m1.008s
   sys    0m13.812s

Marek


On Tue, May 13, 2014 at 3:57 PM, Christian König
<deathsimple at vodafone.de> wrote:
> Am 13.05.2014 15:22, schrieb Alex Deucher:
>
>> On Mon, May 12, 2014 at 7:38 PM, Grigori Goronzy <greg at chown.ath.cx>
>> wrote:
>>>
>>> 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.
>>
>> Allocation overhead?
>
>
> Unlikely, Xonotic just allocates a single page table at start, which then
> gets extended to a certain rate until they no longer need more address space
> and are done with it.
>
> Grigori, can you bisect and/or try to figure out what's wrong here?
>
> Christian.
>
>
>>
>>
>>> 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
>>>>>>>>
>>>>>>>>
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>
>