[PATCH 2/2] drm: Revert syncobj timeline changes.

[zhoucm1]

On 2018年11月12日 18:16, Christian König wrote:
> Am 09.11.18 um 23:26 schrieb Eric Anholt:
>> Eric Anholt<eric at anholt.net>  writes:
>>
>>> [ Unknown signature status ]
>>> zhoucm1<zhoucm1 at amd.com>  writes:
>>>
>>>> On 2018年11月09日 00:52, Christian König wrote:
>>>>> Am 08.11.18 um 17:07 schrieb Koenig, Christian:
>>>>>> Am 08.11.18 um 17:04 schrieb Eric Anholt:
>>>>>>> Daniel suggested I submit this, since we're still seeing regressions
>>>>>>> from it.  This is a revert to before 48197bc564c7 ("drm: add syncobj
>>>>>>> timeline support v9") and its followon fixes.
>>>>>> This is a harmless false positive from lockdep, Chouming and I are
>>>>>> already working on a fix.
>>>>> On the other hand we had enough trouble with that patch, so if it
>>>>> really bothers you feel free to add my Acked-by: Christian König
>>>>> <christian.koenig at amd.com>  and push it.
>>>> NAK, please no, I don't think this needed, the Warning totally isn't
>>>> related to syncobj timeline, but fence-array implementation flaw, just
>>>> exposed by syncobj.
>>>> In addition, Christian already has a fix for this Warning, I've tested.
>>>> Please Christian send to public review.
>>> I backed out my revert of #2 (#1 still necessary) after adding the
>>> lockdep regression fix, and now my CTS run got oomkilled after just a
>>> few hours, with these notable lines in the unreclaimable slab info list:
>>>
>>> [ 6314.373099] drm_sched_fence        69095KB      69095KB
>>> [ 6314.373653] kmemleak_object       428249KB     428384KB
>>> [ 6314.373736] kmalloc-262144           256KB        256KB
>>> [ 6314.373743] kmalloc-131072           128KB        128KB
>>> [ 6314.373750] kmalloc-65536             64KB         64KB
>>> [ 6314.373756] kmalloc-32768           1472KB       1728KB
>>> [ 6314.373763] kmalloc-16384             64KB         64KB
>>> [ 6314.373770] kmalloc-8192             208KB        208KB
>>> [ 6314.373778] kmalloc-4096            2408KB       2408KB
>>> [ 6314.373784] kmalloc-2048             288KB        336KB
>>> [ 6314.373792] kmalloc-1024            1457KB       1512KB
>>> [ 6314.373800] kmalloc-512              854KB       1048KB
>>> [ 6314.373808] kmalloc-256              188KB        268KB
>>> [ 6314.373817] kmalloc-192            69141KB      69142KB
>>> [ 6314.373824] kmalloc-64             47703KB      47704KB
>>> [ 6314.373886] kmalloc-128            46396KB      46396KB
>>> [ 6314.373894] kmem_cache                31KB         35KB
>>>
>>> No results from kmemleak, though.
>> OK, it looks like the #2 revert probably isn't related to the OOM issue.
Before you judge if it is memleak, to be honest, you can scan it first.

>> Running a single job on otherwise unused DRM, watching /proc/slabinfo
>> every second for drm_sched_fence, I get:
>>
>> drm_sched_fence        0      0    192   21    1 : tunables   32   16    8 : slabdata      0      0      0 : globalstat       0      0     0    0    0    0    0    0    0 : cpustat      0      0      0      0
>> drm_sched_fence       16     21    192   21    1 : tunables   32   16    8 : slabdata      1      1      0 : globalstat      16     16     1    0    0    0    0    0    0 : cpustat      5      1      6      0
>> drm_sched_fence       13     21    192   21    1 : tunables   32   16    8 : slabdata      1      1      0 : globalstat      16     16     1    0    0    0    0    0    0 : cpustat      5      1      6      0
>> drm_sched_fence        6     21    192   21    1 : tunables   32   16    8 : slabdata      1      1      0 : globalstat      16     16     1    0    0    0    0    0    0 : cpustat      5      1      6      0
>> drm_sched_fence        4     21    192   21    1 : tunables   32   16    8 : slabdata      1      1      0 : globalstat      16     16     1    0    0    0    0    0    0 : cpustat      5      1      6      0
>> drm_sched_fence        2     21    192   21    1 : tunables   32   16    8 : slabdata      1      1      0 : globalstat      16     16     1    0    0    0    0    0    0 : cpustat      5      1      6      0
>> drm_sched_fence        0     21    192   21    1 : tunables   32   16    8 : slabdata      0      1      0 : globalstat      16     16     1    0    0    0    0    0    0 : cpustat      5      1      6      0
>>
>> So we generate a ton of fences, and I guess free them slowly because of
>> RCU?  And presumably kmemleak was sucking up lots of memory because of
>> how many of these objects were laying around.
>
> That is certainly possible. Another possibility is that we don't drop 
> the reference in dma-fence-array early enough.
>
> E.g. the dma-fence-array will keep the reference to its fences until 
> it is destroyed, which is a bit late when you chain multiple 
> dma-fence-array objects together.
Good point, but need to confirm.

>
> David can you take a look at this and propose a fix? That would 
> probably be good to have fixed in dma-fence-array separately to the 
> timeline work.
Yeah,  I would find a free time for it.

Thanks,
David Zhou
>
> Thanks,
> Christian.
>
>>
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>

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