[PATCH v3 4/4] drm/i915: Use __sg_alloc_table_from_pages for userptr allocations

From: Tvrtko Ursulin
Date: Fri Nov 11 2016 - 03:59:31 EST


From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

With the addition of __sg_alloc_table_from_pages we can control
the maximum coallescing size and eliminate a separate path for
allocating backing store here.

Similar to 871dfbd67d4e ("drm/i915: Allow compaction upto
SWIOTLB max segment size") this enables more compact sg lists to
be created and so has a beneficial effect on workloads with many
and/or large objects of this class.

v2:
* Rename helper to i915_sg_segment_size and fix swiotlb override.
* Commit message update.

v3:
* Actually include the swiotlb override fix.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_drv.h | 11 +++++++++++
drivers/gpu/drm/i915/i915_gem.c | 15 +--------------
drivers/gpu/drm/i915/i915_gem_userptr.c | 28 ++++++----------------------
3 files changed, 18 insertions(+), 36 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 30777dee3f9c..38a555c9c44b 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -4175,4 +4175,15 @@ int remap_io_mapping(struct vm_area_struct *vma,
__T; \
})

+static inline unsigned int i915_sg_segment_size(void)
+{
+#if IS_ENABLED(CONFIG_SWIOTLB)
+ unsigned int nr_tbl = swiotlb_nr_tbl();
+
+ return nr_tbl > 0 ? nr_tbl << IO_TLB_SHIFT : UINT_MAX;
+#else
+ return UINT_MAX;
+#endif
+}
+
#endif
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 1c20edba7f2a..cb4c188a395c 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2223,15 +2223,6 @@ void __i915_gem_object_put_pages(struct drm_i915_gem_object *obj,
mutex_unlock(&obj->mm.lock);
}

-static unsigned int swiotlb_max_size(void)
-{
-#if IS_ENABLED(CONFIG_SWIOTLB)
- return rounddown(swiotlb_nr_tbl() << IO_TLB_SHIFT, PAGE_SIZE);
-#else
- return 0;
-#endif
-}
-
static void i915_sg_trim(struct sg_table *orig_st)
{
struct sg_table new_st;
@@ -2267,7 +2258,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
struct sgt_iter sgt_iter;
struct page *page;
unsigned long last_pfn = 0; /* suppress gcc warning */
- unsigned int max_segment;
+ unsigned int max_segment = rounddown(i915_sg_segment_size(), PAGE_SIZE);
int ret;
gfp_t gfp;

@@ -2278,10 +2269,6 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
GEM_BUG_ON(obj->base.read_domains & I915_GEM_GPU_DOMAINS);
GEM_BUG_ON(obj->base.write_domain & I915_GEM_GPU_DOMAINS);

- max_segment = swiotlb_max_size();
- if (!max_segment)
- max_segment = rounddown(UINT_MAX, PAGE_SIZE);
-
st = kmalloc(sizeof(*st), GFP_KERNEL);
if (st == NULL)
return ERR_PTR(-ENOMEM);
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index 64261639f547..b4461f1832a6 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -390,36 +390,20 @@ struct get_pages_work {
struct task_struct *task;
};

-#if IS_ENABLED(CONFIG_SWIOTLB)
-#define swiotlb_active() swiotlb_nr_tbl()
-#else
-#define swiotlb_active() 0
-#endif
-
static int
st_set_pages(struct sg_table **st, struct page **pvec, int num_pages)
{
- struct scatterlist *sg;
- int ret, n;
+ int ret;

*st = kmalloc(sizeof(**st), GFP_KERNEL);
if (*st == NULL)
return -ENOMEM;

- if (swiotlb_active()) {
- ret = sg_alloc_table(*st, num_pages, GFP_KERNEL);
- if (ret)
- goto err;
-
- for_each_sg((*st)->sgl, sg, num_pages, n)
- sg_set_page(sg, pvec[n], PAGE_SIZE, 0);
- } else {
- ret = sg_alloc_table_from_pages(*st, pvec, num_pages,
- 0, num_pages << PAGE_SHIFT,
- GFP_KERNEL);
- if (ret)
- goto err;
- }
+ ret = __sg_alloc_table_from_pages(*st, pvec, num_pages, 0,
+ num_pages << PAGE_SHIFT,
+ GFP_KERNEL, i915_sg_segment_size());
+ if (ret)
+ goto err;

return 0;

--
2.7.4