[Intel-gfx] [PATCH] drm/i915: Optimize the i915_gem_gtt_finish_object function

[Daniel Vetter]

On Fri, Jul 18, 2014 at 1:16 AM, Ben Widawsky <ben at bwidawsk.net> wrote:
> On Fri, Jul 11, 2014 at 10:20:08AM -0700, armin.c.reese at intel.com wrote:
>> From: Armin Reese <armin.c.reese at intel.com>
>>
>> Signed-off-by: Armin Reese <armin.c.reese at intel.com>
>> ---
>>  drivers/gpu/drm/i915/i915_gem_gtt.c | 13 ++++++-------
>>  1 file changed, 6 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
>> index afd4eef..7e2190e 100644
>> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
>> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
>> @@ -1624,18 +1624,17 @@ static void ggtt_unbind_vma(struct i915_vma *vma)
>>
>>  void i915_gem_gtt_finish_object(struct drm_i915_gem_object *obj)
>>  {
>> -     struct drm_device *dev = obj->base.dev;
>> -     struct drm_i915_private *dev_priv = dev->dev_private;
>> -     bool interruptible;
>> -
>> -     interruptible = do_idling(dev_priv);
>> +     if (!obj->has_dma_mapping) {
>> +             struct drm_device *dev = obj->base.dev;
>> +             struct drm_i915_private *dev_priv = dev->dev_private;
>> +             bool interruptible = do_idling(dev_priv);
>>
>> -     if (!obj->has_dma_mapping)
>>               dma_unmap_sg(&dev->pdev->dev,
>>                            obj->pages->sgl, obj->pages->nents,
>>                            PCI_DMA_BIDIRECTIONAL);
>>
>> -     undo_idling(dev_priv, interruptible);
>> +             undo_idling(dev_priv, interruptible);
>> +     }
>>  }
>>
>>  static void i915_gtt_color_adjust(struct drm_mm_node *node,
>
> Note that this doesn't do much on platforms you care about.

To elaborate: This w/a is _only_ used on ironlake when the iommu is
enabled. Also the performance impact of it is so disastrous that any
kind of optimization is pointless.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch