Re: [PATCH v6 00/22] Add generic memory shrinker to VirtIO-GPU and Panfrost DRM drivers

[Dmitry Osipenko]

Hello Robin,

On 6/28/22 15:31, Robin Murphy wrote:
>> Hello,
>>
>> This patchset introduces memory shrinker for the VirtIO-GPU DRM driver
>> and adds memory purging and eviction support to VirtIO-GPU driver.
>>
>> The new dma-buf locking convention is introduced here as well.
>>
>> During OOM, the shrinker will release BOs that are marked as "not needed"
>> by userspace using the new madvise IOCTL, it will also evict idling BOs
>> to SWAP. The userspace in this case is the Mesa VirGL driver, it will
>> mark
>> the cached BOs as "not needed", allowing kernel driver to release memory
>> of the cached shmem BOs on lowmem situations, preventing OOM kills.
>>
>> The Panfrost driver is switched to use generic memory shrinker.
> 
> I think we still have some outstanding issues here - Alyssa reported
> some weirdness yesterday, so I just tried provoking a low-memory
> condition locally with this series applied and a few debug options
> enabled, and the results as below were... interesting.

The warning and crash that you got actually are the minor issues.

Alyssa caught an interesting PREEMPT_DEBUG issue in the shrinker that I
haven't seen before.

She is also experiencing another problem in the Panfrost driver with a
bad shmem pages (I think). It is unrelated to this patchset and
apparently require an extra setup for the reproduction.

-- 
Best regards,
Dmitry