On Fri, Apr 24, 2015 at 03:10:20PM +0300, Joonas Lahtinen wrote:
> Use partial view for huge BOs (bigger than half the mappable aperture)
> in fault handler so that they can be accessed withough trying to make
> room for them by evicting other objects.
>
> Signed-off-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 67 ++++++++++++++++++++++++++-------------
> 1 file changed, 45 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index c2c1819..eb30cee 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1635,6 +1635,7 @@ int i915_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> struct drm_i915_gem_object *obj = to_intel_bo(vma->vm_private_data);
> struct drm_device *dev = obj->base.dev;
> struct drm_i915_private *dev_priv = dev->dev_private;
> + struct i915_ggtt_view view = i915_ggtt_view_normal;
> pgoff_t page_offset;
> unsigned long pfn;
> int ret = 0;
> @@ -1667,8 +1668,21 @@ int i915_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
> goto unlock;
> }
>
> - /* Now bind it into the GTT if needed */
> - ret = i915_gem_obj_ggtt_pin(obj, 0, PIN_MAPPABLE);
> + /* Use a partial view if the object is bigger than half the aperture. */
> + if (obj->base.size > dev_priv->gtt.mappable_end/2) {
> + static const size_t chunk_size = 256; // 1 MiB
> + memset(&view, 0, sizeof(view));
> + view.type = I915_GGTT_VIEW_PARTIAL;
> + view.params.partial.offset = rounddown(page_offset, chunk_size);
> + view.params.partial.size =
> + min_t(size_t,
> + chunk_size,
> + (vma->vm_end - vma->vm_start)/PAGE_SIZE -
> + view.params.partial.offset);
This isn't what I was imagining.
I was expecting to see error handling inside the fault path if we could
not pin the object. This way we could handle fragmentation or display
objects pinned outside the aperture.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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