[Linaro-mm-sig] Re: [PATCH net-next v8 3/3] net: ethernet: ti: am65-cpsw: Add minimal XDP support

On Mon, 08 Apr 2024 11:38:04 +0200 Julien Panis wrote:

+static struct sk_buff *am65_cpsw_alloc_skb(struct am65_cpsw_rx_chn *rx_chn,

• 			   struct net_device *ndev,
  

• 			   unsigned int len,
  

• 			   int desc_idx,
  

• 			   bool allow_direct)
  

+{

• struct sk_buff *skb;
• struct page *page;
• page = page_pool_dev_alloc_pages(rx_chn->page_pool);
• if (unlikely(!page))

• return NULL;
  

• len += AM65_CPSW_HEADROOM;
• skb = build_skb(page_address(page), len);

You shouldn't build the skb upfront any more. Give the page to the HW, once HW sends you a completion - build the skbs. If build fails (allocation failure) just give the page back to HW. If it succeeds, however, you'll get a skb which is far more likely to be cache hot.

• if (unlikely(!skb)) {

• page_pool_put_full_page(rx_chn->page_pool, page, allow_direct);
  

• rx_chn->pages[desc_idx] = NULL;
  

• return NULL;
  

• }