On Fri, Feb 13, 2015 at 10:34:51AM +0000, Chris Wilson wrote:
> On Fri, Feb 13, 2015 at 10:55:46AM +0100, Daniel Vetter wrote:
> > On Thu, Feb 12, 2015 at 09:03:06PM +0000, Chris Wilson wrote:
> > > On Thu, Feb 12, 2015 at 08:05:02PM +0000, rafael.barbalho@xxxxxxxxx wrote:
> > > > From: Rafael Barbalho <rafael.barbalho@xxxxxxxxx>
> > > >
> > > > 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.
> > >
> > > Not quite. You need an active refcount as we do not expect close(fd) to
> > > stall. The trick is to "simply" use requests to retire vma (as well as
> > > the object management it does today, though that just becomes a second
> > > layer for GEM API management, everything else goes through vma).
> >
> > Linking into the ctx unref should give us that for free since requests do
> > hold a reference on the context. So this will only be run when the buffers
> > are idle.
> >
> > Well except that our unbind code is too dense to do that correctly for
> > shared buffers, so we need to move obj->active to vma->active first.
>
> We unbind vma, so what do you mean?
The unbind of the vma will block since we track active per-obj instead of
per-vma. Which is kinda not that cool for a kref_put cleanup function.
But yeah the below is what I had in mind too, with the mentioned nuisance
fixed.
-Daniel
>
> This is how I forsee the code:
>
> static int context_idr_cleanup(int id, void *p, void *data)
> {
> struct intel_context *ctx = p;
>
> if (ctx->ppgtt && !i915_gem_context_is_default(ctx)) {
> struct list_head *list;
> struct i915_vma *vma;
>
> /* Decouple the remaining vma to keep the next lookup fast */
> list = &ctx->ppgtt->base.vma_list;
> while (!list_empty(list)) {
> vma = list_first_entry(list, typeof(*vma), vm_link);
> list_del_init(&vma->vm_link);
> list_del_init(&vma->obj_link);
> i915_vma_put(vma);
> }
>
> /* Drop active references to this vm upon retire */
> ctx->ppgtt->base.closed = true;
>
> /* Drop all inactive references (via vma->vm reference) */
> list = &ctx->ppgtt->base.inactive_list;
> while (!list_empty(list)) {
> struct drm_i915_gem_object *obj;
> int ret;
>
> vma = list_first_entry(list, typeof(*vma), mm_list);
> obj = vma->obj;
>
> drm_gem_object_reference(&obj->base);
> ret = i915_vma_unbind(vma);
> drm_gem_object_unreference(&obj->base);
> if (WARN_ON(ret))
> break;
> }
> }
>
> ctx->file_priv = NULL;
> i915_gem_context_unreference(ctx);
>
> return 0;
> }
> -Chris
>
> --
> Chris Wilson, Intel Open Source Technology Centre
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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