drm/i915: Use __sg_alloc_table_from_pages for userptr allocations

With the addition of __sg_alloc_table_from_pages we can control
the maximum coalescing 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.

v4:
 * Regroup parameters a bit. (Chris Wilson)

v5:
 * Rebase for swiotlb_max_segment.
 * Add DMA map failure handling as in abb0deacb5a6
   ("drm/i915: Fallback to single PAGE_SIZE segments for DMA remapping").

v6: Handle swiotlb_max_segment() returning 1. (Joonas Lahtinen)

v7: Rebase.
v8: Commit spelling fix.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170803091417.23677-1-tvrtko.ursulin@linux.intel.com

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index c1aef3a..2b08bbf 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2828,6 +2828,21 @@ static inline struct scatterlist *__sg_next(struct scatterlist *sg)
             (((__iter).curr += PAGE_SIZE) < (__iter).max) ||           \
             ((__iter) = __sgt_iter(__sg_next((__iter).sgp), false), 0))
 
+static inline unsigned int i915_sg_segment_size(void)
+{
+       unsigned int size = swiotlb_max_segment();
+
+       if (size == 0)
+               return SCATTERLIST_MAX_SEGMENT;
+
+       size = rounddown(size, PAGE_SIZE);
+       /* swiotlb_max_segment_size can return 1 byte when it means one page. */
+       if (size < PAGE_SIZE)
+               size = PAGE_SIZE;
+
+       return size;
+}
+
 static inline const struct intel_device_info *
 intel_info(const struct drm_i915_private *dev_priv)
 {

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 1545a4e..4dffeba 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2303,7 +2303,7 @@ 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 = i915_sg_segment_size();
        gfp_t noreclaim;
        int ret;
 
@@ -2314,10 +2314,6 @@ 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_segment();
-       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 f152a38..2ce078e 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -399,64 +399,42 @@ 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;
-
-       *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;
-       }
-
-       return 0;
-
-err:
-       kfree(*st);
-       *st = NULL;
-       return ret;
-}
-
 static struct sg_table *
-__i915_gem_userptr_set_pages(struct drm_i915_gem_object *obj,
-                            struct page **pvec, int num_pages)
+__i915_gem_userptr_alloc_pages(struct drm_i915_gem_object *obj,
+                              struct page **pvec, int num_pages)
 {
-       struct sg_table *pages;
+       unsigned int max_segment = i915_sg_segment_size();
+       struct sg_table *st;
        int ret;
 
-       ret = st_set_pages(&pages, pvec, num_pages);
-       if (ret)
+       st = kmalloc(sizeof(*st), GFP_KERNEL);
+       if (!st)
+               return ERR_PTR(-ENOMEM);
+
+alloc_table:
+       ret = __sg_alloc_table_from_pages(st, pvec, num_pages,
+                                         0, num_pages << PAGE_SHIFT,
+                                         max_segment,
+                                         GFP_KERNEL);
+       if (ret) {
+               kfree(st);
                return ERR_PTR(ret);
+       }
 
-       ret = i915_gem_gtt_prepare_pages(obj, pages);
+       ret = i915_gem_gtt_prepare_pages(obj, st);
        if (ret) {
-               sg_free_table(pages);
-               kfree(pages);
+               sg_free_table(st);
+
+               if (max_segment > PAGE_SIZE) {
+                       max_segment = PAGE_SIZE;
+                       goto alloc_table;
+               }
+
+               kfree(st);
                return ERR_PTR(ret);
        }
 
-       return pages;
+       return st;
 }
 
 static int
@@ -540,7 +518,8 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
                struct sg_table *pages = ERR_PTR(ret);
 
                if (pinned == npages) {
-                       pages = __i915_gem_userptr_set_pages(obj, pvec, npages);
+                       pages = __i915_gem_userptr_alloc_pages(obj, pvec,
+                                                              npages);
                        if (!IS_ERR(pages)) {
                                __i915_gem_object_set_pages(obj, pages);
                                pinned = 0;
@@ -661,7 +640,7 @@ i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
                pages = __i915_gem_userptr_get_pages_schedule(obj);
                active = pages == ERR_PTR(-EAGAIN);
        } else {
-               pages = __i915_gem_userptr_set_pages(obj, pvec, num_pages);
+               pages = __i915_gem_userptr_alloc_pages(obj, pvec, num_pages);
                active = !IS_ERR(pages);
        }
        if (active)