Re: [PATCH 06/10] drm/i915: Choose not to evict faultable objects from the GGTT

Chris Wilson
2016-08-12T11:13:17Z

On Fri, Aug 12, 2016 at 01:50:56PM +0300, Joonas Lahtinen wrote:
> On pe, 2016-08-12 at 11:28 +0100, Chris Wilson wrote:
> > @@ -1715,10 +1716,10 @@ int i915_gem_fault(struct vm_area_struct *area, struct vm_fault *vmf)
> >   goto err_unlock;
> >   }
> >
> > - /* Use a partial view if the object is bigger than the aperture. */
> > - /* Now pin it into the GTT if needed */
> > - vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,
> > -        PIN_MAPPABLE | PIN_NONBLOCK);
> > + flags = PIN_MAPPABLE;
> > + if (obj->base.size > 2 << 20)
>
> Magic number.

One day there may be a MiB() macro. It is a magic number, just a rule of
thumb based on minimum chunksize for a partial.

> > @@ -55,6 +55,9 @@ mark_free(struct i915_vma *vma, struct list_head *unwind)
> >   if (WARN_ON(!list_empty(&vma->exec_list)))
> >   return false;
> >
> > + if (flags & PIN_NOFAULT && vma->obj->fault_mappable)
> > + return false;
>
> The flag name is rather counter-intuitive for it describes other VMAs
> rather than our new VMA...

As does NONBLOCKING. We could loose this flag in favour of NOEVICT, but
I haven't run anything to confirm if that's a good tradeoff.
-Chris

--
Chris Wilson, Intel Open Source Technology Centre