On Tue, Jan 24, 2017 at 04:19:28PM +0100, Olivier Matz wrote:
> Set the value of m->refcnt to 1, m->nb_segs to 1 and m->next
> to NULL when the mbuf is stored inside the mempool (unused).
> This is done in rte_pktmbuf_prefree_seg(), before freeing or
> recycling a mbuf.
>
> Before this patch, the value of m->refcnt was expected to be 0
> while in pool.
>
> The objectives are:
>
> - to avoid drivers to set m->next to NULL in the early Rx path, since
> this field is in the second 64B of the mbuf and its access could
> trigger a cache miss
>
> - rationalize the behavior of raw_alloc/raw_free: one is now the
> symmetric of the other, and refcnt is never changed in these functions.
>
> Signed-off-by: Olivier Matz <olivier.m...@6wind.com>
> ---
> drivers/net/mlx5/mlx5_rxtx.c | 5 ++---
> drivers/net/mpipe/mpipe_tilegx.c | 1 +
> lib/librte_mbuf/rte_mbuf.c | 2 ++
> lib/librte_mbuf/rte_mbuf.h | 45
> +++++++++++++++++++++++++++++-----------
> 4 files changed, 38 insertions(+), 15 deletions(-)
>
<snip>
> /* compat with older versions */
> __rte_deprecated
> -static inline void __attribute__((always_inline))
> +static inline void
> __rte_mbuf_raw_free(struct rte_mbuf *m)
> {
> rte_mbuf_raw_free(m);
> @@ -1218,8 +1232,12 @@ static inline void rte_pktmbuf_detach(struct rte_mbuf
> *m)
> m->data_len = 0;
> m->ol_flags = 0;
>
> - if (rte_mbuf_refcnt_update(md, -1) == 0)
> + if (rte_mbuf_refcnt_update(md, -1) == 0) {
Minor nit, but in the case that we only have a single reference to the
mbufs, we are always setting that to zero just to re-increment it to 1
again.
> + md->next = NULL;
> + md->nb_segs = 1;
> + rte_mbuf_refcnt_set(md, 1);
> rte_mbuf_raw_free(md);
> + }
> }
>
> /**
