Re: [Intel-gfx] [PATCH 1/3] drm/i915: Map the ringbuffer using WB on LLC machines

[Ville Syrjälä]

On Thu, Oct 08, 2015 at 01:39:54PM +0100, Chris Wilson wrote:
> If we have llc coherency, we can write directly into the ringbuffer
> using ordinary cached writes rather than forcing WC access.
> 
> v2: An important consequence is that we can forgo the mappable request
> for WB ringbuffers, allowing for many more simultaneous contexts.

Fits in with my understanding on llc coherency.

Reviewed-by: Ville Syrjälä 

> 
> Signed-off-by: Chris Wilson 
> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 70 
> ++---
>  1 file changed, 56 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c 
> b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index d608be46ea6e..f81ec7785fac 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -1966,11 +1966,35 @@ static int init_phys_status_page(struct 
> intel_engine_cs *ring)
>  
>  void intel_unpin_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
>  {
> - iounmap(ringbuf->virtual_start);
> + if (HAS_LLC(ringbuf->obj->base.dev) && !ringbuf->obj->stolen)
> + vunmap(ringbuf->virtual_start);
> + else
> + iounmap(ringbuf->virtual_start);
>   ringbuf->virtual_start = NULL;
>   i915_gem_object_ggtt_unpin(ringbuf->obj);
>  }
>  
> +static u32 *vmap_obj(struct drm_i915_gem_object *obj)
> +{
> + struct sg_page_iter sg_iter;
> + struct page **pages;
> + void *addr;
> + int i;
> +
> + pages = drm_malloc_ab(obj->base.size >> PAGE_SHIFT, sizeof(*pages));
> + if (pages == NULL)
> + return NULL;
> +
> + i = 0;
> + for_each_sg_page(obj->pages->sgl, _iter, obj->pages->nents, 0)
> + pages[i++] = sg_page_iter_page(_iter);
> +
> + addr = vmap(pages, i, 0, PAGE_KERNEL);
> + drm_free_large(pages);
> +
> + return addr;
> +}
> +
>  int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
>struct intel_ringbuffer *ringbuf)
>  {
> @@ -1978,21 +2002,39 @@ int intel_pin_and_map_ringbuffer_obj(struct 
> drm_device *dev,
>   struct drm_i915_gem_object *obj = ringbuf->obj;
>   int ret;
>  
> - ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, PIN_MAPPABLE);
> - if (ret)
> - return ret;
> + if (HAS_LLC(dev_priv) && !obj->stolen) {
> + ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, 0);
> + if (ret)
> + return ret;
>  
> - ret = i915_gem_object_set_to_gtt_domain(obj, true);
> - if (ret) {
> - i915_gem_object_ggtt_unpin(obj);
> - return ret;
> - }
> + ret = i915_gem_object_set_to_cpu_domain(obj, true);
> + if (ret) {
> + i915_gem_object_ggtt_unpin(obj);
> + return ret;
> + }
> +
> + ringbuf->virtual_start = vmap_obj(obj);
> + if (ringbuf->virtual_start == NULL) {
> + i915_gem_object_ggtt_unpin(obj);
> + return -ENOMEM;
> + }
> + } else {
> + ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, PIN_MAPPABLE);
> + if (ret)
> + return ret;
>  
> - ringbuf->virtual_start = ioremap_wc(dev_priv->gtt.mappable_base +
> - i915_gem_obj_ggtt_offset(obj), ringbuf->size);
> - if (ringbuf->virtual_start == NULL) {
> - i915_gem_object_ggtt_unpin(obj);
> - return -EINVAL;
> + ret = i915_gem_object_set_to_gtt_domain(obj, true);
> + if (ret) {
> + i915_gem_object_ggtt_unpin(obj);
> + return ret;
> + }
> +
> + ringbuf->virtual_start = ioremap_wc(dev_priv->gtt.mappable_base 
> +
> + 
> i915_gem_obj_ggtt_offset(obj), ringbuf->size);
> + if (ringbuf->virtual_start == NULL) {
> + i915_gem_object_ggtt_unpin(obj);
> + return -EINVAL;
> + }
>   }
>  
>   return 0;
> -- 
> 2.6.1
> 
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-- 
Ville Syrjälä
Intel OTC
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[Intel-gfx] [PATCH 1/3] drm/i915: Map the ringbuffer using WB on LLC machines

[Chris Wilson]

If we have llc coherency, we can write directly into the ringbuffer
using ordinary cached writes rather than forcing WC access.

v2: An important consequence is that we can forgo the mappable request
for WB ringbuffers, allowing for many more simultaneous contexts.

Signed-off-by: Chris Wilson 
---
 drivers/gpu/drm/i915/intel_ringbuffer.c | 70 ++---
 1 file changed, 56 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c 
b/drivers/gpu/drm/i915/intel_ringbuffer.c
index d608be46ea6e..f81ec7785fac 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1966,11 +1966,35 @@ static int init_phys_status_page(struct intel_engine_cs 
*ring)
 
 void intel_unpin_ringbuffer_obj(struct intel_ringbuffer *ringbuf)
 {
-   iounmap(ringbuf->virtual_start);
+   if (HAS_LLC(ringbuf->obj->base.dev) && !ringbuf->obj->stolen)
+   vunmap(ringbuf->virtual_start);
+   else
+   iounmap(ringbuf->virtual_start);
ringbuf->virtual_start = NULL;
i915_gem_object_ggtt_unpin(ringbuf->obj);
 }
 
+static u32 *vmap_obj(struct drm_i915_gem_object *obj)
+{
+   struct sg_page_iter sg_iter;
+   struct page **pages;
+   void *addr;
+   int i;
+
+   pages = drm_malloc_ab(obj->base.size >> PAGE_SHIFT, sizeof(*pages));
+   if (pages == NULL)
+   return NULL;
+
+   i = 0;
+   for_each_sg_page(obj->pages->sgl, _iter, obj->pages->nents, 0)
+   pages[i++] = sg_page_iter_page(_iter);
+
+   addr = vmap(pages, i, 0, PAGE_KERNEL);
+   drm_free_large(pages);
+
+   return addr;
+}
+
 int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
 struct intel_ringbuffer *ringbuf)
 {
@@ -1978,21 +2002,39 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device 
*dev,
struct drm_i915_gem_object *obj = ringbuf->obj;
int ret;
 
-   ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, PIN_MAPPABLE);
-   if (ret)
-   return ret;
+   if (HAS_LLC(dev_priv) && !obj->stolen) {
+   ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, 0);
+   if (ret)
+   return ret;
 
-   ret = i915_gem_object_set_to_gtt_domain(obj, true);
-   if (ret) {
-   i915_gem_object_ggtt_unpin(obj);
-   return ret;
-   }
+   ret = i915_gem_object_set_to_cpu_domain(obj, true);
+   if (ret) {
+   i915_gem_object_ggtt_unpin(obj);
+   return ret;
+   }
+
+   ringbuf->virtual_start = vmap_obj(obj);
+   if (ringbuf->virtual_start == NULL) {
+   i915_gem_object_ggtt_unpin(obj);
+   return -ENOMEM;
+   }
+   } else {
+   ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, PIN_MAPPABLE);
+   if (ret)
+   return ret;
 
-   ringbuf->virtual_start = ioremap_wc(dev_priv->gtt.mappable_base +
-   i915_gem_obj_ggtt_offset(obj), ringbuf->size);
-   if (ringbuf->virtual_start == NULL) {
-   i915_gem_object_ggtt_unpin(obj);
-   return -EINVAL;
+   ret = i915_gem_object_set_to_gtt_domain(obj, true);
+   if (ret) {
+   i915_gem_object_ggtt_unpin(obj);
+   return ret;
+   }
+
+   ringbuf->virtual_start = ioremap_wc(dev_priv->gtt.mappable_base 
+
+   
i915_gem_obj_ggtt_offset(obj), ringbuf->size);
+   if (ringbuf->virtual_start == NULL) {
+   i915_gem_object_ggtt_unpin(obj);
+   return -EINVAL;
+   }
}
 
return 0;
-- 
2.6.1

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