Re: [PATCH net-next v2] net/mlx5: allocate DMA pool structs on the pool's NUMA node

[Jacob Keller]

On 10/6/2026 7:16 AM, Seongjun Hong wrote:
> The mlx5 DMA pool structs (mlx5_dma_pool, mlx5_dma_pool_page and its
> block bitmap, and mlx5_frag_buf_node_pools) are allocated without a
> node hint, so they land on the node of whichever CPU happens to create
> or fill the pool, while the DMA pages they describe are allocated on
> the pool's node.
> 
> The pool, page and bitmap are dereferenced on every block allocation
> and free. Allocate them on the pool's NUMA node as well, so that all
> of a pool's state lives on one node.
> 
> These allocations happen on the control path, so the performance gain
> is expected to be small; the change is mainly for consistency.
> 
> Signed-off-by: Seongjun Hong <hsj0512@xxxxxxxxx>
> ---
> Changes in v2:
> - fix typo and specify the structs are allocated on the control path
> - add a prefix net-next to the subject
> - Link to v1: https://lore.kernel.org/r/20261005-net-mlx5-numa-allocate-pool-page-v1-1-01f4283932b4@xxxxxxxxx
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/alloc.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/alloc.c b/drivers/net/ethernet/mellanox/mlx5/core/alloc.c
> index a92cf545bdaf..dcd281c4691d 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/alloc.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/alloc.c
> @@ -110,7 +110,7 @@ static struct mlx5_dma_pool *mlx5_dma_pool_create(struct mlx5_core_dev *dev,
>  {
>  	struct mlx5_dma_pool *pool;
>  
> -	pool = kzalloc_obj(*pool);
> +	pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, node);

This removes all the benefits of kzalloc_obj() here...

But I guess the __alloc_objs API doesn'thave the ability to add a node?
It seems like we'd benefit from having support for the node parameter..
but it does seem tricky to add. kzalloc_node_obj() could potentially be
added. Staring at the implementation I have no idea how complicated that
would be.

Still, this only really changes two allocations and they're pretty
obviously correct.

Reviewed-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>

>  	if (!pool)
>  		return NULL;
>  
> @@ -127,19 +127,20 @@ mlx5_dma_pool_page_alloc(struct mlx5_dma_pool *pool)
>  {
>  	int blocks_per_page = BIT(PAGE_SHIFT - pool->block_shift);
>  	struct mlx5_dma_pool_page *page;
> +	int node = pool->node;
>  
> -	page = kzalloc_obj(*page);
> +	page = kzalloc_node(sizeof(*page), GFP_KERNEL, node);
>  	if (!page)
>  		goto err_out;
>  
>  	page->pool = pool;
> -	page->bitmap = bitmap_zalloc(blocks_per_page, GFP_KERNEL);
> +	page->bitmap = bitmap_zalloc_node(blocks_per_page, GFP_KERNEL, node);
>  	if (!page->bitmap)
>  		goto err_free_page;
>  
>  	bitmap_fill(page->bitmap, blocks_per_page);
>  	page->buf = mlx5_dma_zalloc_coherent_node(pool->dev, PAGE_SIZE,
> -						  &page->dma, pool->node);
> +						  &page->dma, node);
>  	if (!page->buf)
>  		goto err_free_bitmap;
>  
> @@ -278,7 +279,7 @@ mlx5_frag_buf_node_pools_create(struct mlx5_core_dev *dev, int node)
>  {
>  	struct mlx5_frag_buf_node_pools *node_pools;
>  
> -	node_pools = kzalloc_obj(*node_pools);
> +	node_pools = kzalloc_node(sizeof(*node_pools), GFP_KERNEL, node);
>  	if (!node_pools)
>  		return NULL;
>  
> 
> ---
> base-commit: 8b4e7209c842d8cb9516f1f5ef0a88aa2d8831a6
> change-id: 20261005-net-mlx5-numa-allocate-pool-page-2ee20a04147e
> 
> Best regards,