[Mesa-dev] [PATCH 12.5/18] anv/allocator: Tweak the block pool growing algorithm

[Juan A. Suarez Romero]

Reviewed-by: Juan A. Suarez Romero <jasuarez at igalia.com>


On Wed, 2017-04-26 at 10:01 -0700, Jason Ekstrand wrote:
> The old algorithm worked fine assuming a constant block size.  We're
> about to break that assumption so we need an algorithm that's a bit more
> robust against suddenly growing by a huge amount compared to the
> currently allocated quantity of memory.
> ---
>  src/intel/vulkan/anv_allocator.c | 28 ++++++++++++++++++----------
>  1 file changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/src/intel/vulkan/anv_allocator.c b/src/intel/vulkan/anv_allocator.c
> index 05666ec..8728d42 100644
> --- a/src/intel/vulkan/anv_allocator.c
> +++ b/src/intel/vulkan/anv_allocator.c
> @@ -433,7 +433,6 @@ static uint32_t
>  anv_block_pool_grow(struct anv_block_pool *pool, struct anv_block_state *state,
>                      uint32_t block_size)
>  {
> -   uint32_t size;
>     VkResult result = VK_SUCCESS;
>  
>     pthread_mutex_lock(&pool->device->mutex);
> @@ -458,9 +457,19 @@ anv_block_pool_grow(struct anv_block_pool *pool, struct anv_block_state *state,
>  
>     uint32_t old_size = pool->bo.size;
>  
> -   if (old_size != 0 &&
> -       back_used * 2 <= pool->center_bo_offset &&
> -       front_used * 2 <= (old_size - pool->center_bo_offset)) {
> +   /* The block pool is always initialized to a nonzero size and this function
> +    * is always called after initialization.
> +    */
> +   assert(old_size > 0);
> +
> +   /* The back_used and front_used may actually be smaller than the actual
> +    * requirement because they are based on the next pointers which are
> +    * updated prior to calling this function.
> +    */
> +   uint32_t back_required = MAX2(back_used, pool->center_bo_offset);
> +   uint32_t front_required = MAX2(front_used, old_size - pool->center_bo_offset);
> +
> +   if (back_used * 2 <= back_required && front_used * 2 <= front_required) {
>        /* If we're in this case then this isn't the firsta allocation and we
>         * already have enough space on both sides to hold double what we
>         * have allocated.  There's nothing for us to do.
> @@ -468,12 +477,11 @@ anv_block_pool_grow(struct anv_block_pool *pool, struct anv_block_state *state,
>        goto done;
>     }
>  
> -   if (old_size == 0) {
> -      /* This is the first allocation */
> -      size = MAX2(32 * block_size, PAGE_SIZE);
> -   } else {
> -      size = old_size * 2;
> -   }
> +   uint32_t size = old_size * 2;
> +   while (size < back_required + front_required)
> +      size *= 2;
> +
> +   assert(size > pool->bo.size);
>  
>     /* We can't have a block pool bigger than 1GB because we use signed
>      * 32-bit offsets in the free list and we don't want overflow.  We