Re: [dpdk-dev] [PATCH v4] mbuf: fix mbuf free performance with non atomic refcnt

[Ilya Matveychikov <matvejchikov@gmail.com>]

Olivier,

> On Dec 8, 2017, at 7:46 PM, Olivier Matz <olivier.matz@6wind.com> wrote:
> 

> 
> lib/librte_mbuf/rte_mbuf.h | 23 ++++++++++++++++++-----
> 1 file changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index ce8a05ddf..dd08cb72b 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -764,6 +764,13 @@ rte_mbuf_refcnt_set(struct rte_mbuf *m, uint16_t new_value)
> 	rte_atomic16_set(&m->refcnt_atomic, new_value);
> }
> 
> +/* internal */
> +static inline uint16_t
> +__rte_mbuf_refcnt_update(struct rte_mbuf *m, int16_t value)
> +{
> +	return (uint16_t)(rte_atomic16_add_return(&m->refcnt_atomic, value));

What’s the purpose of using direct cast to uint16_t here and in other places?

> +}
> +
> /**
>  * Adds given value to an mbuf's refcnt and returns its new value.
>  * @param m
> @@ -788,19 +795,26 @@ rte_mbuf_refcnt_update(struct rte_mbuf *m, int16_t value)
> 		return 1 + value;
> 	}
> 
> -	return (uint16_t)(rte_atomic16_add_return(&m->refcnt_atomic, value));
> +	return __rte_mbuf_refcnt_update(m, value);
> }
> 
> #else /* ! RTE_MBUF_REFCNT_ATOMIC */
> 
> +/* internal */
> +static inline uint16_t
> +__rte_mbuf_refcnt_update(struct rte_mbuf *m, int16_t value)
> +{
> +	m->refcnt = (uint16_t)(m->refcnt + value);
> +	return m->refcnt;
> +}
> +
> /**
>  * Adds given value to an mbuf's refcnt and returns its new value.
>  */
> static inline uint16_t
> rte_mbuf_refcnt_update(struct rte_mbuf *m, int16_t value)
> {
> -	m->refcnt = (uint16_t)(m->refcnt + value);
> -	return m->refcnt;
> +	return __rte_mbuf_refcnt_update(m, value);
> }
> 
> /**
> @@ -1364,8 +1378,7 @@ rte_pktmbuf_prefree_seg(struct rte_mbuf *m)
> 
> 		return m;
> 
> -       } else if (rte_atomic16_add_return(&m->refcnt_atomic, -1) == 0) {
> -
> +	} else if (__rte_mbuf_refcnt_update(m, -1) == 0) {
> 
> 		if (RTE_MBUF_INDIRECT(m))
> 			rte_pktmbuf_detach(m);
> -- 
> 2.11.0
>