Re: [PATCH 8/8] drm/panfrost: Make sure the shrinker does not reclaim referenced BOs

[Boris Brezillon <boris.brezillon@collabora.com>]

On Fri, 29 Nov 2019 15:48:15 +0000
Steven Price <steven.price@arm.com> wrote:

> On 29/11/2019 13:59, Boris Brezillon wrote:
> > Userspace might tag a BO purgeable while it's still referenced by GPU
> > jobs. We need to make sure the shrinker does not purge such BOs until
> > all jobs referencing it are finished.
> > 
> > Fixes: 013b65101315 ("drm/panfrost: Add madvise and shrinker support")
> > Cc: <stable@vger.kernel.org>
> > Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>  
> 
> I'm happy with this, but I would also argue that it was previously user
> space's job not to mark a BO purgeable while it's in use by the GPU.

I was not aware of this design choice.

> This is in some ways an ABI change so we should be sure this is
> something that we want to support "forever" more.

Well, in that case, the ABI change is bringing extra robustness, with
AFAICT, no downside for those that were taking care of that in
userspace.

> But if Mesa has
> 'always' been assuming this behaviour we might as well match.

I think so, and VC4 seems to have the same expectations.

> 
> Reviewed-by: Steven Price <steven.price@arm.com>

Thanks for the review.