Subject: Re: [PATCH net-next v5 5/5] mvneta: recycle buffers

From: "Russell King (Oracle)" <[email-masked]>
Date: Thu, 13 May 2021 19:25:54 +0100

On Thu, May 13, 2021 at 06:58:46PM +0200, Matteo Croce wrote:
> From: Matteo Croce <[email-masked]>
> 
> Use the new recycling API for page_pool.
> In a drop rate test, the packet rate increased di 10%,

Typo - "by" ?

> from 269 Kpps to 296 Kpps.
> 
> perf top on a stock system shows:
> 
> Overhead  Shared Object     Symbol
>   21.78%  [kernel]          [k] __pi___inval_dcache_area
>   21.66%  [mvneta]          [k] mvneta_rx_swbm
>    7.00%  [kernel]          [k] kmem_cache_alloc
>    6.05%  [kernel]          [k] eth_type_trans
>    4.44%  [kernel]          [k] kmem_cache_free.part.0
>    3.80%  [kernel]          [k] __netif_receive_skb_core
>    3.68%  [kernel]          [k] dev_gro_receive
>    3.65%  [kernel]          [k] get_page_from_freelist
>    3.43%  [kernel]          [k] page_pool_release_page
>    3.35%  [kernel]          [k] free_unref_page
> 
> And this is the same output with recycling enabled:
> 
> Overhead  Shared Object     Symbol
>   24.10%  [kernel]          [k] __pi___inval_dcache_area
>   23.02%  [mvneta]          [k] mvneta_rx_swbm
>    7.19%  [kernel]          [k] kmem_cache_alloc
>    6.50%  [kernel]          [k] eth_type_trans
>    4.93%  [kernel]          [k] __netif_receive_skb_core
>    4.77%  [kernel]          [k] kmem_cache_free.part.0
>    3.93%  [kernel]          [k] dev_gro_receive
>    3.03%  [kernel]          [k] build_skb
>    2.91%  [kernel]          [k] page_pool_put_page
>    2.85%  [kernel]          [k] __xdp_return
> 
> The test was done with mausezahn on the TX side with 64 byte raw
> ethernet frames.
> 
> Signed-off-by: Matteo Croce <[email-masked]>

Other than the typo, I have no objection to the patch.

Acked-by: Russell King (Oracle) <[email-masked]>

> ---
>  drivers/net/ethernet/marvell/mvneta.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index 7d5cd9bc6c99..6d2f8dce4900 100644
> --- a/drivers/net/ethernet/marvell/mvneta.c
> +++ b/drivers/net/ethernet/marvell/mvneta.c
> @@ -2320,7 +2320,7 @@ mvneta_swbm_add_rx_fragment(struct mvneta_port *pp,
>  }
>  
>  static struct sk_buff *
> -mvneta_swbm_build_skb(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
> +mvneta_swbm_build_skb(struct mvneta_port *pp, struct page_pool *pool,
>  		      struct xdp_buff *xdp, u32 desc_status)
>  {
>  	struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp);
> @@ -2331,7 +2331,7 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
>  	if (!skb)
>  		return ERR_PTR(-ENOMEM);
>  
> -	page_pool_release_page(rxq->page_pool, virt_to_page(xdp->data));
> +	skb_mark_for_recycle(skb, virt_to_page(xdp->data), pool);
>  
>  	skb_reserve(skb, xdp->data - xdp->data_hard_start);
>  	skb_put(skb, xdp->data_end - xdp->data);
> @@ -2343,7 +2343,10 @@ mvneta_swbm_build_skb(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
>  		skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
>  				skb_frag_page(frag), skb_frag_off(frag),
>  				skb_frag_size(frag), PAGE_SIZE);
> -		page_pool_release_page(rxq->page_pool, skb_frag_page(frag));
> +		/* We don't need to reset pp_recycle here. It's already set, so
> +		 * just mark fragments for recycling.
> +		 */
> +		page_pool_store_mem_info(skb_frag_page(frag), pool);
>  	}
>  
>  	return skb;
> @@ -2425,7 +2428,7 @@ static int mvneta_rx_swbm(struct napi_struct *napi,
>  		    mvneta_run_xdp(pp, rxq, xdp_prog, &xdp_buf, frame_sz, &ps))
>  			goto next;
>  
> -		skb = mvneta_swbm_build_skb(pp, rxq, &xdp_buf, desc_status);
> +		skb = mvneta_swbm_build_skb(pp, pp, &xdp_buf, desc_status);
>  		if (IS_ERR(skb)) {
>  			struct mvneta_pcpu_stats *stats = this_cpu_ptr(pp->stats);
>  
> -- 
> 2.31.1
> 
> 

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