Re: [Intel-gfx] [PATCH 15/41] drm/i915: Use radixtree to jump start intel_partial_pages()

[Tvrtko Ursulin]

On 14/10/2016 13:18, Chris Wilson wrote:

We can use the radixtree index of the obj->pages to find the start
position of the desired partial range.

Signed-off-by: Chris Wilson 
---
  drivers/gpu/drm/i915/i915_gem_gtt.c | 40 -
  1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c 
b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 2bbbda191e93..b3f341fe77bf 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -3584,35 +3584,47 @@ intel_partial_pages(const struct i915_ggtt_view *view,
struct drm_i915_gem_object *obj)
  {
struct sg_table *st;
-   struct scatterlist *sg;
-   struct sg_page_iter obj_sg_iter;
+   struct scatterlist *sg, *iter;
+   unsigned int count = view->params.partial.size;
+   unsigned int offset;
int ret = -ENOMEM;
  
  	st = kmalloc(sizeof(*st), GFP_KERNEL);

if (!st)
goto err_st_alloc;
  
-	ret = sg_alloc_table(st, view->params.partial.size, GFP_KERNEL);

+   ret = sg_alloc_table(st, count, GFP_KERNEL);
if (ret)
goto err_sg_alloc;
  
+	iter = i915_gem_object_get_sg(obj,

+ view->params.partial.offset,
+ );
+   GEM_BUG_ON(!iter);
+
sg = st->sgl;
st->nents = 0;
-   for_each_sg_page(obj->pages->sgl, _sg_iter, obj->pages->nents,
-   view->params.partial.offset)
-   {
-   if (st->nents >= view->params.partial.size)
-   break;
+   do {
+   unsigned int len;
  
-		sg_set_page(sg, NULL, PAGE_SIZE, 0);

-   sg_dma_address(sg) = sg_page_iter_dma_address(_sg_iter);
-   sg_dma_len(sg) = PAGE_SIZE;
+   len = min(iter->length - (offset << PAGE_SHIFT),
+ count << PAGE_SHIFT);
+   sg_set_page(sg, NULL, len, 0);
+   sg_dma_address(sg) =
+   sg_dma_address(iter) + (offset << PAGE_SHIFT);
+   sg_dma_len(sg) = len;
  
-		sg = sg_next(sg);

st->nents++;
-   }
+   count -= len >> PAGE_SHIFT;
+   if (count == 0) {
+   sg_mark_end(sg);
+   return st;
+   }
  
-	return st;

+   sg = __sg_next(sg);
+   iter = __sg_next(iter);
+   offset = 0;
+   } while (1);
  
  err_sg_alloc:

kfree(st);


Looks OK and I trust you when you say it is faster.

Reviewed-by: Tvrtko Ursulin 

Regards,

Tvrtko

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[Intel-gfx] [PATCH 15/41] drm/i915: Use radixtree to jump start intel_partial_pages()

[Chris Wilson]

We can use the radixtree index of the obj->pages to find the start
position of the desired partial range.

Signed-off-by: Chris Wilson 
---
 drivers/gpu/drm/i915/i915_gem_gtt.c | 40 -
 1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c 
b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 2bbbda191e93..b3f341fe77bf 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -3584,35 +3584,47 @@ intel_partial_pages(const struct i915_ggtt_view *view,
struct drm_i915_gem_object *obj)
 {
struct sg_table *st;
-   struct scatterlist *sg;
-   struct sg_page_iter obj_sg_iter;
+   struct scatterlist *sg, *iter;
+   unsigned int count = view->params.partial.size;
+   unsigned int offset;
int ret = -ENOMEM;
 
st = kmalloc(sizeof(*st), GFP_KERNEL);
if (!st)
goto err_st_alloc;
 
-   ret = sg_alloc_table(st, view->params.partial.size, GFP_KERNEL);
+   ret = sg_alloc_table(st, count, GFP_KERNEL);
if (ret)
goto err_sg_alloc;
 
+   iter = i915_gem_object_get_sg(obj,
+ view->params.partial.offset,
+ );
+   GEM_BUG_ON(!iter);
+
sg = st->sgl;
st->nents = 0;
-   for_each_sg_page(obj->pages->sgl, _sg_iter, obj->pages->nents,
-   view->params.partial.offset)
-   {
-   if (st->nents >= view->params.partial.size)
-   break;
+   do {
+   unsigned int len;
 
-   sg_set_page(sg, NULL, PAGE_SIZE, 0);
-   sg_dma_address(sg) = sg_page_iter_dma_address(_sg_iter);
-   sg_dma_len(sg) = PAGE_SIZE;
+   len = min(iter->length - (offset << PAGE_SHIFT),
+ count << PAGE_SHIFT);
+   sg_set_page(sg, NULL, len, 0);
+   sg_dma_address(sg) =
+   sg_dma_address(iter) + (offset << PAGE_SHIFT);
+   sg_dma_len(sg) = len;
 
-   sg = sg_next(sg);
st->nents++;
-   }
+   count -= len >> PAGE_SHIFT;
+   if (count == 0) {
+   sg_mark_end(sg);
+   return st;
+   }
 
-   return st;
+   sg = __sg_next(sg);
+   iter = __sg_next(iter);
+   offset = 0;
+   } while (1);
 
 err_sg_alloc:
kfree(st);
-- 
2.9.3

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