Re: [dpdk-dev] [PATCH v6 1/2] kni: add bulk function to free mbufs

[Olivier Matz <olivier.matz@6wind.com>]

Hi,

On Thu, 19 Jan 2017 11:46:58 +0700, Sergey Vyazmitinov
<s.vyazmitinov@brain4net.com> wrote:
> Suggested-by: Stephen Hemminger <stephen@networkplumber.org>
> Signed-off-by: Sergey Vyazmitinov <s.vyazmitinov@brain4net.com>
> ---
> v3:
> * Fixed issue with possible different mempools in buffer list.
> * Fixed issue with wrong rte_pktmbuf_alloc_bulk function return value
> processing in the kni_allocate_mbufs.
> ---
>  lib/librte_mbuf/rte_mbuf.h | 49
> ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49
> insertions(+)
> 
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 4476d75..69d314f 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -306,6 +306,9 @@ extern "C" {
>  /** Alignment constraint of mbuf private area. */
>  #define RTE_MBUF_PRIV_ALIGN 8
>  
> +/** Maximum number of mbufs freed in bulk. */
> +#define RTE_MBUF_BULK_FREE 64
> +
>  /**
>   * Get the name of a RX offload flag
>   *
> @@ -1261,6 +1264,52 @@ static inline void rte_pktmbuf_free(struct
> rte_mbuf *m) }
>  
>  /**
> + * Free n packets mbuf back into its original mempool.
> + *
> + * Free each mbuf, and all its segments in case of chained buffers.
> Each
> + * segment is added back into its original mempool.
> + *
> + * @param mp
> + *   The packets mempool.

This parameter was removed, it could be removed from the API comment.


> + * @param mbufs
> + *   The packets mbufs array to be freed.
> + * @param n
> + *   Number of packets.
> + */
> +static inline void rte_pktmbuf_free_bulk(struct rte_mbuf **mbufs,
> +		unsigned int n)

I suggest we could use mbuf instead of pktmbuf in the function name.
It's a bit shorter, and the function would also apply on ctrlmbuf.

Also, the struct rte_mbuf **mbufs could probably be replaced by struct
rte_mbuf * const *mbufs.


> +{
> +	void *tofree[RTE_MBUF_BULK_FREE];
> +	struct rte_mempool *mp = NULL;
> +	unsigned int i, count = 0;
> +
> +	for (i = 0; i < n; i++) {
> +		struct rte_mbuf *m, *m_next;
> +
> +		for (m = mbufs[i]; m; m = m_next) {
> +			m_next = m->next;
> +
> +			if (count > 0 &&
> +			    (unlikely(m->pool != mp ||
> +				    count == RTE_MBUF_BULK_FREE))) {
> +				rte_mempool_put_bulk(mp, tofree,
> count);
> +				count = 0;
> +			}
> +
> +			mp = m->pool;
> +
> +			if (likely(__rte_pktmbuf_prefree_seg(m) !=
> NULL)) {
> +				m->next = NULL;
> +				tofree[count++] = m;
> +			}
> +		}
> +	}
> +
> +	if (likely(count > 0))
> +		rte_mempool_put_bulk(mp, tofree, count);
> +}
> +
> +/**
>   * Creates a "clone" of the given packet mbuf.
>   *

The function looks good to me, thank you. It looks also better than
what I've suggested in [1], since it properly manage mbuf chains. On
the other hand, I think my proposal could also help in drivers, where
segments are already unchained. I'll submit it in a RFC.

[1] http://dpdk.org/ml/archives/dev/2017-January/054538.html


One more thing, maybe it's worth adding a basic test in
app/test/test_mbuf.c.

Thanks,
Olivier