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SubjectRe: [PATCH 7/9] drm/vmwgfx: Use an RBtree instead of linked list for MOB resources
Date
Reviewed-by: Deepak Rawat <drawat@vmware.com>

On Fri, 2019-04-12 at 09:04 -0700, Thomas Hellstrom wrote:
> With emulated coherent memory we need to be able to quickly look up
> a resource from the MOB offset. Instead of traversing a linked list
> with
> O(n) worst case, use an RBtree with O(log n) worst case complexity.
>
> Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
> ---
> drivers/gpu/drm/vmwgfx/vmwgfx_bo.c | 5 ++--
> drivers/gpu/drm/vmwgfx/vmwgfx_drv.h | 10 +++----
> drivers/gpu/drm/vmwgfx/vmwgfx_resource.c | 33 +++++++++++++++++-----
> --
> 3 files changed, 32 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_bo.c
> b/drivers/gpu/drm/vmwgfx/vmwgfx_bo.c
> index 90ca866640fe..e8bc7a7ac031 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_bo.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_bo.c
> @@ -464,6 +464,7 @@ void vmw_bo_bo_free(struct ttm_buffer_object *bo)
> struct vmw_buffer_object *vmw_bo = vmw_buffer_object(bo);
>
> WARN_ON(vmw_bo->dirty);
> + WARN_ON(!RB_EMPTY_ROOT(&vmw_bo->res_tree));
> vmw_bo_unmap(vmw_bo);
> kfree(vmw_bo);
> }
> @@ -480,6 +481,7 @@ static void vmw_user_bo_destroy(struct
> ttm_buffer_object *bo)
> struct vmw_buffer_object *vbo = &vmw_user_bo->vbo;
>
> WARN_ON(vbo->dirty);
> + WARN_ON(!RB_EMPTY_ROOT(&vbo->res_tree));
> vmw_bo_unmap(vbo);
> ttm_prime_object_kfree(vmw_user_bo, prime);
> }
> @@ -515,8 +517,7 @@ int vmw_bo_init(struct vmw_private *dev_priv,
> memset(vmw_bo, 0, sizeof(*vmw_bo));
> BUILD_BUG_ON(TTM_MAX_BO_PRIORITY <= 3);
> vmw_bo->base.priority = 3;
> -
> - INIT_LIST_HEAD(&vmw_bo->res_list);
> + vmw_bo->res_tree = RB_ROOT;
>
> ret = ttm_bo_init(bdev, &vmw_bo->base, size,
> ttm_bo_type_device, placement,
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> index f05fce52fbb4..81ebcd668038 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
> @@ -90,7 +90,7 @@ struct vmw_fpriv {
> /**
> * struct vmw_buffer_object - TTM buffer object with vmwgfx
> additions
> * @base: The TTM buffer object
> - * @res_list: List of resources using this buffer object as a
> backing MOB
> + * @res_tree: RB tree of resources using this buffer object as a
> backing MOB
> * @pin_count: pin depth
> * @dx_query_ctx: DX context if this buffer object is used as a DX
> query MOB
> * @map: Kmap object for semi-persistent mappings
> @@ -99,7 +99,7 @@ struct vmw_fpriv {
> */
> struct vmw_buffer_object {
> struct ttm_buffer_object base;
> - struct list_head res_list;
> + struct rb_root res_tree;
> s32 pin_count;
> /* Not ref-counted. Protected by binding_mutex */
> struct vmw_resource *dx_query_ctx;
> @@ -147,8 +147,8 @@ struct vmw_res_func;
> * pin-count greater than zero. It is not on the resource LRU lists
> and its
> * backup buffer is pinned. Hence it can't be evicted.
> * @func: Method vtable for this resource. Immutable.
> + * @mob_node; Node for the MOB backup rbtree. Protected by @backup
> reserved.
> * @lru_head: List head for the LRU list. Protected by
> @dev_priv::resource_lock.
> - * @mob_head: List head for the MOB backup list. Protected by
> @backup reserved.
> * @binding_head: List head for the context binding list. Protected
> by
> * the @dev_priv::binding_mutex
> * @res_free: The resource destructor.
> @@ -169,8 +169,8 @@ struct vmw_resource {
> unsigned long backup_offset;
> unsigned long pin_count;
> const struct vmw_res_func *func;
> + struct rb_node mob_node;
> struct list_head lru_head;
> - struct list_head mob_head;
> struct list_head binding_head;
> struct vmw_resource_dirty *dirty;
> void (*res_free) (struct vmw_resource *res);
> @@ -743,7 +743,7 @@ void vmw_resource_dirty_update(struct
> vmw_resource *res, pgoff_t start,
> */
> static inline bool vmw_resource_mob_attached(const struct
> vmw_resource *res)
> {
> - return !list_empty(&res->mob_head);
> + return !RB_EMPTY_NODE(&res->mob_node);
> }
>
> /**
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
> b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
> index d35f4bd32cd9..ff9fe5650468 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
> @@ -41,11 +41,24 @@
> void vmw_resource_mob_attach(struct vmw_resource *res)
> {
> struct vmw_buffer_object *backup = res->backup;
> + struct rb_node **new = &backup->res_tree.rb_node, *parent =
> NULL;
>
> lockdep_assert_held(&backup->base.resv->lock.base);
> res->used_prio = (res->res_dirty) ? res->func->dirty_prio :
> res->func->prio;
> - list_add_tail(&res->mob_head, &backup->res_list);
> +
> + while (*new) {
> + struct vmw_resource *this =
> + container_of(*new, struct vmw_resource,
> mob_node);
> +
> + parent = *new;
> + new = (res->backup_offset < this->backup_offset) ?
> + &((*new)->rb_left) : &((*new)->rb_right);
> + }
> +
> + rb_link_node(&res->mob_node, parent, new);
> + rb_insert_color(&res->mob_node, &backup->res_tree);
> +
> vmw_bo_prio_add(backup, res->used_prio);
> }
>
> @@ -59,7 +72,8 @@ void vmw_resource_mob_detach(struct vmw_resource
> *res)
>
> lockdep_assert_held(&backup->base.resv->lock.base);
> if (vmw_resource_mob_attached(res)) {
> - list_del_init(&res->mob_head);
> + rb_erase(&res->mob_node, &backup->res_tree);
> + RB_CLEAR_NODE(&res->mob_node);
> vmw_bo_prio_del(backup, res->used_prio);
> }
> }
> @@ -206,8 +220,8 @@ int vmw_resource_init(struct vmw_private
> *dev_priv, struct vmw_resource *res,
> res->res_free = res_free;
> res->dev_priv = dev_priv;
> res->func = func;
> + RB_CLEAR_NODE(&res->mob_node);
> INIT_LIST_HEAD(&res->lru_head);
> - INIT_LIST_HEAD(&res->mob_head);
> INIT_LIST_HEAD(&res->binding_head);
> res->id = -1;
> res->backup = NULL;
> @@ -755,19 +769,20 @@ int vmw_resource_validate(struct vmw_resource
> *res, bool intr)
> */
> void vmw_resource_unbind_list(struct vmw_buffer_object *vbo)
> {
> -
> - struct vmw_resource *res, *next;
> struct ttm_validate_buffer val_buf = {
> .bo = &vbo->base,
> .num_shared = 0
> };
>
> lockdep_assert_held(&vbo->base.resv->lock.base);
> - list_for_each_entry_safe(res, next, &vbo->res_list, mob_head) {
> - if (!res->func->unbind)
> - continue;
> + while (!RB_EMPTY_ROOT(&vbo->res_tree)) {
> + struct rb_node *node = vbo->res_tree.rb_node;
> + struct vmw_resource *res =
> + container_of(node, struct vmw_resource,
> mob_node);
> +
> + if (!WARN_ON_ONCE(!res->func->unbind))
> + (void) res->func->unbind(res, res->res_dirty,
> &val_buf);
>
> - (void) res->func->unbind(res, res->res_dirty,
> &val_buf);
> res->backup_dirty = true;
> res->res_dirty = false;
> vmw_resource_mob_detach(res);
> --
> 2.20.1
>

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