[dpdk-dev] [PATCH] fix ceph async messenger runtime bug based on spdk/dpdk

[Liu, Chunmei]

But if not initialize allocated mbuf->next = NULL, when do ip package assemble, the last mbuf->next maybe not be null, all the logical has error, the application use null pointer determine a packaged end. DPDK NIC doesn't work now.

-----Original Message-----
From: Stephen Hemminger [mailto:stephen at networkplumber.org] 
Sent: Wednesday, December 13, 2017 1:31 PM
To: Liu, Chunmei <chunmei.liu at intel.com>
Cc: dev at dpdk.org
Subject: Re: [dpdk-dev] [PATCH] fix ceph async messenger runtime bug based on spdk/dpdk

On Wed, 13 Dec 2017 11:32:32 -0800
chunmei Liu <chunmei.liu at intel.com> wrote:

> diff --git a/drivers/net/ixgbe/ixgbe_rxtx.c 
> b/drivers/net/ixgbe/ixgbe_rxtx.c index 1e07895..30fdbc1 100644
> --- a/drivers/net/ixgbe/ixgbe_rxtx.c
> +++ b/drivers/net/ixgbe/ixgbe_rxtx.c
> @@ -1589,6 +1589,7 @@ ixgbe_rx_alloc_bufs(struct ixgbe_rx_queue *rxq, bool reset_mbuf)
>  		}
>  
>  		rte_mbuf_refcnt_set(mb, 1);
> +		mb->next = NULL;
>  		mb->data_off = RTE_PKTMBUF_HEADROOM;
>  

This will have measurable performance impact because the next pointer is on the second cache line.