diff mbox series

[v3,08/12] drm/i915/ttm: add tt shmem backend

Message ID 20210915185954.3114858-8-matthew.auld@intel.com (mailing list archive)
State New, archived
Headers show
Series [v3,01/12] drm/ttm: stop setting page->index for the ttm_tt | expand

Commit Message

Matthew Auld Sept. 15, 2021, 6:59 p.m. UTC
For cached objects we can allocate our pages directly in shmem. This
should make it possible(in a later patch) to utilise the existing
i915-gem shrinker code for such objects. For now this is still disabled.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_object.h |   8 +
 drivers/gpu/drm/i915/gem/i915_gem_shmem.c  |  14 +-
 drivers/gpu/drm/i915/gem/i915_gem_ttm.c    | 217 ++++++++++++++++++---
 3 files changed, 209 insertions(+), 30 deletions(-)

Comments

Thomas Hellstrom Sept. 16, 2021, 1:45 p.m. UTC | #1
On Wed, 2021-09-15 at 19:59 +0100, Matthew Auld wrote:
> For cached objects we can allocate our pages directly in shmem. This
> should make it possible(in a later patch) to utilise the existing
> i915-gem shrinker code for such objects. For now this is still
> disabled.
> 
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Cc: Christian König <christian.koenig@amd.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_object.h |   8 +
>  drivers/gpu/drm/i915/gem/i915_gem_shmem.c  |  14 +-
>  drivers/gpu/drm/i915/gem/i915_gem_ttm.c    | 217 ++++++++++++++++++-
> --
>  3 files changed, 209 insertions(+), 30 deletions(-)
> 
> 

...

>  }
> @@ -223,6 +349,10 @@ static bool i915_ttm_eviction_valuable(struct
> ttm_buffer_object *bo,
>  {
>         struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
>  
> +       if (place->mem_type == TTM_PL_SYSTEM &&
> +           bo->ttm && bo->ttm->page_flags & I915_TTM_TT_SHMEM)
> +               return false;
> +


Should we use ttm_bo_pin() / ttm_bo_unpin() to remove the bo from the
TTM LRU lists when it's SHMEM populated, and change the above to a
GEM_BUG_ON()?


>         /* Will do for now. Our pinned objects are still on TTM's LRU
> lists */
>         return i915_gem_object_evictable(obj);
>  }
> @@ -316,9 +446,11 @@ static void
> i915_ttm_adjust_gem_after_move(struct drm_i915_gem_object *obj)
>         i915_gem_object_set_cache_coherency(obj, cache_level);
>  }
>  
> -static void i915_ttm_purge(struct drm_i915_gem_object *obj)
> +static void i915_ttm_writeback(struct drm_i915_gem_object *obj)
>  {
>         struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
> +       struct i915_ttm_tt *i915_tt =
> +               container_of(bo->ttm, typeof(*i915_tt), ttm);
>         struct ttm_operation_ctx ctx = {
>                 .interruptible = true,
>                 .no_wait_gpu = false,
> @@ -326,18 +458,52 @@ static void i915_ttm_purge(struct
> drm_i915_gem_object *obj)
>         struct ttm_placement place = {};
>         int ret;
>  
> -       if (obj->mm.madv == __I915_MADV_PURGED)
> +       if (!bo->ttm || !(bo->ttm->page_flags & I915_TTM_TT_SHMEM))
>                 return;
>  
> -       /* TTM's purge interface. Note that we might be reentering.
> */
> +       i915_tt->backup = true;
>         ret = ttm_bo_validate(bo, &place, &ctx);

It looks like writeback() becomes the backend's primary callback for
shrinking, although for the shmem backend, this is put_pages(), and the
writeback() callback is only called if needed to accelerate shmem's
transfer of pages to the swap cache. It appears like this will break
the shrinker reporting of shrunken pages?

Should we try to do the primary shrinking from the put_pages() callback
instead, like the shmem backend? Although we'd have to allow NULL pages
in put_pages() to account for evicted-to-shmem and adjust other
backends if necessary.



> -       if (!ret) {
> -               obj->write_domain = 0;
> -               obj->read_domains = 0;
> -               i915_ttm_adjust_gem_after_move(obj);
> -               i915_ttm_free_cached_io_st(obj);
> -               obj->mm.madv = __I915_MADV_PURGED;
> +       i915_tt->backup = false;
> +       if (ret)
> +               return;
> +
> +       __shmem_writeback(obj->base.size, i915_tt->filp->f_mapping);
> +}
> +
diff mbox series

Patch

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
index 48112b9d76df..561d6bd0a5c9 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
@@ -618,6 +618,14 @@  int i915_gem_object_wait_migration(struct drm_i915_gem_object *obj,
 bool i915_gem_object_placement_possible(struct drm_i915_gem_object *obj,
 					enum intel_memory_type type);
 
+struct sg_table *shmem_alloc_st(struct drm_i915_private *i915,
+				size_t size, struct intel_memory_region *mr,
+				struct address_space *mapping,
+				unsigned int max_segment);
+void shmem_free_st(struct sg_table *st, struct address_space *mapping,
+		   bool dirty, bool backup);
+void __shmem_writeback(size_t size, struct address_space *mapping);
+
 #ifdef CONFIG_MMU_NOTIFIER
 static inline bool
 i915_gem_object_is_userptr(struct drm_i915_gem_object *obj)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
index 36b711ae9e28..19e55cc29a15 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_shmem.c
@@ -25,8 +25,8 @@  static void check_release_pagevec(struct pagevec *pvec)
 	cond_resched();
 }
 
-static void shmem_free_st(struct sg_table *st, struct address_space *mapping,
-			  bool dirty, bool backup)
+void shmem_free_st(struct sg_table *st, struct address_space *mapping,
+		   bool dirty, bool backup)
 {
 	struct sgt_iter sgt_iter;
 	struct pagevec pvec;
@@ -52,10 +52,10 @@  static void shmem_free_st(struct sg_table *st, struct address_space *mapping,
 	kfree(st);
 }
 
-static struct sg_table *shmem_alloc_st(struct drm_i915_private *i915,
-				       size_t size, struct intel_memory_region *mr,
-				       struct address_space *mapping,
-				       unsigned int max_segment)
+struct sg_table *shmem_alloc_st(struct drm_i915_private *i915,
+				size_t size, struct intel_memory_region *mr,
+				struct address_space *mapping,
+				unsigned int max_segment)
 {
 	const unsigned long page_count = size / PAGE_SIZE;
 	unsigned long i;
@@ -300,7 +300,7 @@  shmem_truncate(struct drm_i915_gem_object *obj)
 	obj->mm.pages = ERR_PTR(-EFAULT);
 }
 
-static void __shmem_writeback(size_t size, struct address_space *mapping)
+void __shmem_writeback(size_t size, struct address_space *mapping)
 {
 	struct writeback_control wbc = {
 		.sync_mode = WB_SYNC_NONE,
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
index aefaf9293005..a93e3a9ef698 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
@@ -32,11 +32,17 @@ 
  */
 #define I915_TTM_MAX_PLACEMENTS INTEL_REGION_UNKNOWN
 
+/* In our ttm backend external objects translate to the shmem_tt backend */
+#define I915_TTM_TT_SHMEM TTM_PAGE_FLAG_EXTERNAL_MAPPABLE
+
 /**
  * struct i915_ttm_tt - TTM page vector with additional private information
  * @ttm: The base TTM page vector.
  * @dev: The struct device used for dma mapping and unmapping.
  * @cached_st: The cached scatter-gather table.
+ * @obj: The GEM object. Should be valid while we have a valid bo->ttm.
+ * @filp: The shmem file, if using shmem backend.
+ * @backup: Swap out the pages when unpopulating, if using shmem backend.
  *
  * Note that DMA may be going on right up to the point where the page-
  * vector is unpopulated in delayed destroy. Hence keep the
@@ -48,6 +54,9 @@  struct i915_ttm_tt {
 	struct ttm_tt ttm;
 	struct device *dev;
 	struct sg_table *cached_st;
+	struct drm_i915_gem_object *obj;
+	struct file *filp;
+	bool backup;
 };
 
 static const struct ttm_place sys_placement_flags = {
@@ -167,12 +176,105 @@  i915_ttm_placement_from_obj(const struct drm_i915_gem_object *obj,
 	placement->busy_placement = busy;
 }
 
+static int i915_ttm_tt_shmem_populate(struct ttm_device *bdev,
+				      struct ttm_tt *ttm,
+				      struct ttm_operation_ctx *ctx)
+{
+	struct drm_i915_private *i915 = container_of(bdev, typeof(*i915), bdev);
+	struct intel_memory_region *mr = i915->mm.regions[INTEL_MEMORY_SYSTEM];
+	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
+	const unsigned int max_segment = i915_sg_segment_size();
+	const size_t size = ttm->num_pages << PAGE_SHIFT;
+	struct drm_i915_gem_object *obj = i915_tt->obj;
+	struct file *filp = i915_tt->filp;
+	struct sgt_iter sgt_iter;
+	struct sg_table *st;
+	struct page *page;
+	unsigned long i;
+	int err;
+
+	GEM_BUG_ON(obj->mm.madv != I915_MADV_WILLNEED);
+
+	if (!filp) {
+		struct address_space *mapping;
+		gfp_t mask;
+
+		filp = shmem_file_setup("i915-shmem-tt", size, VM_NORESERVE);
+		if (IS_ERR(filp))
+			return PTR_ERR(filp);
+
+		mask = GFP_HIGHUSER | __GFP_RECLAIMABLE;
+
+		mapping = filp->f_mapping;
+		mapping_set_gfp_mask(mapping, mask);
+		GEM_BUG_ON(!(mapping_gfp_mask(mapping) & __GFP_RECLAIM));
+
+		i915_tt->filp = filp;
+	}
+
+	st = shmem_alloc_st(i915, size, mr, filp->f_mapping, max_segment);
+	if (IS_ERR(st))
+		return PTR_ERR(st);
+
+	err = dma_map_sg_attrs(i915_tt->dev,
+			       st->sgl, st->nents,
+			       PCI_DMA_BIDIRECTIONAL,
+			       DMA_ATTR_SKIP_CPU_SYNC |
+			       DMA_ATTR_NO_KERNEL_MAPPING |
+			       DMA_ATTR_NO_WARN);
+	if (err <= 0) {
+		err = -EINVAL;
+		goto err_free_st;
+	}
+
+	i = 0;
+	for_each_sgt_page(page, sgt_iter, st)
+		ttm->pages[i++] = page;
+
+	if (ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)
+		ttm->page_flags &= ~TTM_PAGE_FLAG_SWAPPED;
+
+	i915_tt->cached_st = st;
+	return 0;
+
+err_free_st:
+	shmem_free_st(st, filp->f_mapping, false, false);
+	return err;
+}
+
+static void i915_ttm_tt_shmem_unpopulate(struct ttm_tt *ttm)
+{
+	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
+	struct drm_i915_gem_object *obj = i915_tt->obj;
+	bool backup = i915_tt->backup;
+
+	if (obj->mm.madv == I915_MADV_DONTNEED) {
+		obj->mm.dirty = false;
+		GEM_BUG_ON(backup);
+	}
+
+	dma_unmap_sg(i915_tt->dev, i915_tt->cached_st->sgl,
+		     i915_tt->cached_st->nents,
+		     PCI_DMA_BIDIRECTIONAL);
+
+	shmem_free_st(i915_tt->cached_st,
+		      file_inode(i915_tt->filp)->i_mapping,
+		      obj->mm.dirty, backup);
+	i915_tt->cached_st = NULL;
+
+	obj->mm.dirty = false;
+
+	if (backup)
+		ttm->page_flags |= TTM_PAGE_FLAG_SWAPPED;
+}
+
 static struct ttm_tt *i915_ttm_tt_create(struct ttm_buffer_object *bo,
 					 uint32_t page_flags)
 {
 	struct ttm_resource_manager *man =
 		ttm_manager_type(bo->bdev, bo->resource->mem_type);
 	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
+	enum ttm_caching caching = i915_ttm_select_tt_caching(obj);
 	struct i915_ttm_tt *i915_tt;
 	int ret;
 
@@ -184,36 +286,60 @@  static struct ttm_tt *i915_ttm_tt_create(struct ttm_buffer_object *bo,
 	    man->use_tt)
 		page_flags |= TTM_PAGE_FLAG_ZERO_ALLOC;
 
-	ret = ttm_tt_init(&i915_tt->ttm, bo, page_flags,
-			  i915_ttm_select_tt_caching(obj));
-	if (ret) {
-		kfree(i915_tt);
-		return NULL;
-	}
+	if (i915_gem_object_is_shrinkable(obj) && caching == ttm_cached)
+		page_flags |= I915_TTM_TT_SHMEM;
+
+	ret = ttm_tt_init(&i915_tt->ttm, bo, page_flags, caching);
+	if (ret)
+		goto err_free;
 
 	i915_tt->dev = obj->base.dev->dev;
+	i915_tt->obj = obj;
 
 	return &i915_tt->ttm;
+
+err_free:
+	kfree(i915_tt);
+	return NULL;
+}
+
+static int i915_ttm_tt_populate(struct ttm_device *bdev,
+				struct ttm_tt *ttm,
+				struct ttm_operation_ctx *ctx)
+{
+	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
+
+	if (ttm->page_flags & I915_TTM_TT_SHMEM)
+		return i915_ttm_tt_shmem_populate(bdev, ttm, ctx);
+
+	return ttm_pool_alloc(&bdev->pool, ttm, ctx);
 }
 
 static void i915_ttm_tt_unpopulate(struct ttm_device *bdev, struct ttm_tt *ttm)
 {
 	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
 
-	if (i915_tt->cached_st) {
-		dma_unmap_sgtable(i915_tt->dev, i915_tt->cached_st,
-				  DMA_BIDIRECTIONAL, 0);
-		sg_free_table(i915_tt->cached_st);
-		kfree(i915_tt->cached_st);
-		i915_tt->cached_st = NULL;
+	if (ttm->page_flags & I915_TTM_TT_SHMEM) {
+		i915_ttm_tt_shmem_unpopulate(ttm);
+	} else {
+		if (i915_tt->cached_st) {
+			dma_unmap_sgtable(i915_tt->dev, i915_tt->cached_st,
+					  DMA_BIDIRECTIONAL, 0);
+			sg_free_table(i915_tt->cached_st);
+			kfree(i915_tt->cached_st);
+			i915_tt->cached_st = NULL;
+		}
+		ttm_pool_free(&bdev->pool, ttm);
 	}
-	ttm_pool_free(&bdev->pool, ttm);
 }
 
 static void i915_ttm_tt_destroy(struct ttm_device *bdev, struct ttm_tt *ttm)
 {
 	struct i915_ttm_tt *i915_tt = container_of(ttm, typeof(*i915_tt), ttm);
 
+	if (i915_tt->filp)
+		fput(i915_tt->filp);
+
 	ttm_tt_fini(ttm);
 	kfree(i915_tt);
 }
@@ -223,6 +349,10 @@  static bool i915_ttm_eviction_valuable(struct ttm_buffer_object *bo,
 {
 	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
 
+	if (place->mem_type == TTM_PL_SYSTEM &&
+	    bo->ttm && bo->ttm->page_flags & I915_TTM_TT_SHMEM)
+		return false;
+
 	/* Will do for now. Our pinned objects are still on TTM's LRU lists */
 	return i915_gem_object_evictable(obj);
 }
@@ -316,9 +446,11 @@  static void i915_ttm_adjust_gem_after_move(struct drm_i915_gem_object *obj)
 	i915_gem_object_set_cache_coherency(obj, cache_level);
 }
 
-static void i915_ttm_purge(struct drm_i915_gem_object *obj)
+static void i915_ttm_writeback(struct drm_i915_gem_object *obj)
 {
 	struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
+	struct i915_ttm_tt *i915_tt =
+		container_of(bo->ttm, typeof(*i915_tt), ttm);
 	struct ttm_operation_ctx ctx = {
 		.interruptible = true,
 		.no_wait_gpu = false,
@@ -326,18 +458,52 @@  static void i915_ttm_purge(struct drm_i915_gem_object *obj)
 	struct ttm_placement place = {};
 	int ret;
 
-	if (obj->mm.madv == __I915_MADV_PURGED)
+	if (!bo->ttm || !(bo->ttm->page_flags & I915_TTM_TT_SHMEM))
 		return;
 
-	/* TTM's purge interface. Note that we might be reentering. */
+	i915_tt->backup = true;
 	ret = ttm_bo_validate(bo, &place, &ctx);
-	if (!ret) {
-		obj->write_domain = 0;
-		obj->read_domains = 0;
-		i915_ttm_adjust_gem_after_move(obj);
-		i915_ttm_free_cached_io_st(obj);
-		obj->mm.madv = __I915_MADV_PURGED;
+	i915_tt->backup = false;
+	if (ret)
+		return;
+
+	__shmem_writeback(obj->base.size, i915_tt->filp->f_mapping);
+}
+
+static void i915_ttm_purge(struct drm_i915_gem_object *obj)
+{
+	struct ttm_buffer_object *bo = i915_gem_to_ttm(obj);
+	struct ttm_operation_ctx ctx = {
+		.interruptible = true,
+		.no_wait_gpu = false,
+	};
+	struct ttm_placement place = {};
+
+	if (obj->mm.madv == __I915_MADV_PURGED)
+		return;
+
+	if (ttm_bo_validate(bo, &place, &ctx))
+		return;
+
+	if (bo->ttm && bo->ttm->page_flags & I915_TTM_TT_SHMEM) {
+		struct i915_ttm_tt *i915_tt =
+			container_of(bo->ttm, typeof(*i915_tt), ttm);
+
+		GEM_BUG_ON(i915_tt->backup);
+
+		if (i915_tt->filp) {
+			shmem_truncate_range(file_inode(i915_tt->filp),
+					     0, (loff_t)-1);
+			fput(i915_tt->filp);
+			i915_tt->filp = NULL;
+		}
 	}
+
+	obj->write_domain = 0;
+	obj->read_domains = 0;
+	i915_ttm_adjust_gem_after_move(obj);
+	i915_ttm_free_cached_io_st(obj);
+	obj->mm.madv = __I915_MADV_PURGED;
 }
 
 static void i915_ttm_swap_notify(struct ttm_buffer_object *bo)
@@ -605,6 +771,7 @@  static unsigned long i915_ttm_io_mem_pfn(struct ttm_buffer_object *bo,
 
 static struct ttm_device_funcs i915_ttm_bo_driver = {
 	.ttm_tt_create = i915_ttm_tt_create,
+	.ttm_tt_populate = i915_ttm_tt_populate,
 	.ttm_tt_unpopulate = i915_ttm_tt_unpopulate,
 	.ttm_tt_destroy = i915_ttm_tt_destroy,
 	.eviction_valuable = i915_ttm_eviction_valuable,
@@ -678,6 +845,8 @@  static int __i915_ttm_get_pages(struct drm_i915_gem_object *obj,
 			return PTR_ERR(st);
 
 		__i915_gem_object_set_pages(obj, st, i915_sg_dma_sizes(st->sgl));
+		if (!bo->ttm || !(bo->ttm->page_flags & I915_TTM_TT_SHMEM))
+			i915_gem_object_make_unshrinkable(obj);
 	}
 
 	return ret;
@@ -874,9 +1043,12 @@  static const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = {
 	.get_pages = i915_ttm_get_pages,
 	.put_pages = i915_ttm_put_pages,
 	.truncate = i915_ttm_purge,
+	.writeback = i915_ttm_writeback,
+
 	.adjust_lru = i915_ttm_adjust_lru,
 	.delayed_free = i915_ttm_delayed_free,
 	.migrate = i915_ttm_migrate,
+
 	.mmap_offset = i915_ttm_mmap_offset,
 	.mmap_ops = &vm_ops_ttm,
 };
@@ -918,7 +1090,6 @@  int __i915_gem_ttm_object_init(struct intel_memory_region *mem,
 	drm_gem_private_object_init(&i915->drm, &obj->base, size);
 	i915_gem_object_init(obj, &i915_gem_ttm_obj_ops, &lock_class, flags);
 	i915_gem_object_init_memory_region(obj, mem);
-	i915_gem_object_make_unshrinkable(obj);
 	INIT_RADIX_TREE(&obj->ttm.get_io_page.radix, GFP_KERNEL | __GFP_NOWARN);
 	mutex_init(&obj->ttm.get_io_page.lock);
 	bo_type = (obj->flags & I915_BO_ALLOC_USER) ? ttm_bo_type_device :