CIK hangs with kernel 3.15, bisected

Tue May 13 12:50:27 PDT 2014

Hi Christian,

The performance regression I saw with piglit seems to be fixed with
latest kernel git. It's difficult to bisect the kernel, because there
are only merges between 3.14 and 3.15 and the merged committs are
actually based on 3.14-rc1 and 3.14-rc4.

All seems to be fine with your fixes.

Marek

On Tue, May 13, 2014 at 5:31 PM, Christian König
<deathsimple at vodafone.de> wrote:
> Is the performance regression regression caused by the page table changes or
> something else?
>
> I did made some tests with xonotic while developing it and it didn't showed
> anything obvious, but I didn't made tests on different systems.
>
> Christian.
>
> Am 13.05.2014 17:19, schrieb 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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>>>>> http://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>
>>>
>