[Intel-gfx] [RFC 2/2] drm/i915: Clean-up PPGTT on context destruction

[Daniel Vetter]

On Fri, Feb 13, 2015 at 10:05:16AM +0000, Chris Wilson wrote:
> On Fri, Feb 13, 2015 at 10:51:36AM +0100, Daniel Vetter wrote:
> > On Thu, Feb 12, 2015 at 08:05:02PM +0000, rafael.barbalho at intel.com wrote:
> > > From: Rafael Barbalho <rafael.barbalho at intel.com>
> > > 
> > > With full PPGTT enabled an object's VMA entry into a PPGTT VM needs to be
> > > cleaned up so that the PPGTT PDE & PTE allocations can be freed.
> > > 
> > > This problem only shows up with full PPGTT because an object's VMA is
> > > only cleaned-up when the object is destroyed. However, if the object has
> > > been shared between multiple processes this may not happen, which leads to
> > > references to the PPGTT still being kept the object was shared.
> > > 
> > > Under android the sharing of GEM objects is a fairly common operation, thus
> > > the clean-up has to be more agressive.
> > > 
> > > Signed-off-by: Rafael Barbalho <rafael.barbalho at intel.com>
> > > Cc: Daniel Vetter <daniel at ffwll.ch>
> > > Cc: Jon Bloomfield <jon.bloomfield at intel.com>
> > 
> > So when we've merged this we iirc talked about this issue and decided that
> > the shrinker should be good enough in cleaning up the crap from shared
> > objects. Not a pretty solution, but it should have worked.
> > 
> > Is this again the lowmemory killer wreaking havoc with our i915 shrinker,
> > or is there something else going on? And do you have some igt testcase for
> > this? If sharing is all that's required the following should do the trick:
> > 1. allocate obj
> > 2. create new context
> > 3. do dummy execbuf with that obj to map it into the ppgtt
> > 4. free context
> > 5. goto 2 often enough to OOM
> 
> You know I have patches to fix all of this... It just happens to fall
> out of tracking vma in requests, and by extension vm.

Since you replied to my description of the igt testcase ... What kind of
bugs do you mean? I kinda can't find the context here ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch