Re: [dpdk-dev] [PATCH] app: fix refcnt in mbuf allocation

[Adrien Mazarguil <adrien.mazarguil@6wind.com>]

On Mon, May 06, 2013 at 06:00:01PM +0200, Thomas Monjalon wrote:
> From: Dongsu Han <dongsuh@cs.cmu.edu>
> 
> test-pmd txonly leaks mbuf from the pool.
> The function tx_mbuf_alloc() does not change the refcnt
> and the refcnt is 0 when it is first allocated.
> However, rte_pktmbuf_free_seg called by the driver's xmit code decrements
> reference count to -1. So mbuf never goes back to the pool.
> As a result, txonly can't send packets after it exhausts the mempool.
> 
> The function tx_mbuf_alloc() was getting mbuf directly from mempool and so
> was bypassing mbuf API.
> The dedicated function is rte_pktmbuf_alloc() but it is much slower because
> it does unnecessary initializations in rte_pktmbuf_reset().
> By using the internal API __rte_mbuf_raw_alloc(), refcnt is correctly handled
> without adding too much overload.
> 
> Signed-off-by: Dongsu Han <dongsuh@cs.cmu.edu>
> Signed-off-by: Thomas Monjalon <thomas.monjalon@6wind.com>
> ---
>  app/test-pmd/txonly.c |    5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/app/test-pmd/txonly.c b/app/test-pmd/txonly.c
> index d7c8c31..e7c9a1a 100644
> --- a/app/test-pmd/txonly.c
> +++ b/app/test-pmd/txonly.c
> @@ -93,11 +93,8 @@ static inline struct rte_mbuf *
>  tx_mbuf_alloc(struct rte_mempool *mp)
>  {
>  	struct rte_mbuf *m;
> -	void *mb;
>  
> -	if (rte_mempool_get(mp, &mb) < 0)
> -		return NULL;
> -	m = (struct rte_mbuf *)mb;
> +	m = __rte_mbuf_raw_alloc(mp);
>  	__rte_mbuf_sanity_check(m, RTE_MBUF_PKT, 1);
>  	return m;
>  }
> -- 
> 1.7.10.4

Looks good.

Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>

-- 
Adrien Mazarguil
6WIND