RE: [PATCH v3] mbuf: add fast free bulk and raw alloc bulk functions

[Slava Ovsiienko <viacheslavo@nvidia.com>]

Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>

PS. It seems we should consider replacing the rte_mempool_put_bulk()
with the new wrapper rte_mbuf_fast_free_bulk() in the drivers.

> -----Original Message-----
> From: Morten Brørup <mb@smartsharesystems.com>
> Sent: Tuesday, January 21, 2025 3:40 PM
> To: NBU-Contact-Thomas Monjalon (EXTERNAL) <thomas@monjalon.net>;
> Ferruh Yigit <ferruh.yigit@amd.com>; Andrew Rybchenko
> <andrew.rybchenko@oktetlabs.ru>; Slava Ovsiienko
> <viacheslavo@nvidia.com>; Shahaf Shuler <shahafs@nvidia.com>; Olivier
> Matz <olivier.matz@6wind.com>
> Cc: dev@dpdk.org; Morten Brørup <mb@smartsharesystems.com>; Dengdui
> Huang <huangdengdui@huawei.com>
> Subject: [PATCH v3] mbuf: add fast free bulk and raw alloc bulk functions
> 
> When putting an mbuf back into its mempool, there are certain requirements
> to the mbuf. Specifically, some of its fields must be initialized.
> 
> These requirements are in fact invariants about free mbufs, held in
> mempools, and thus also apply when allocating an mbuf from a mempool.
> With this in mind, the additional assertions in rte_mbuf_raw_free() were
> moved to __rte_mbuf_raw_sanity_check().
> Furthermore, the assertion regarding pinned external buffer was enhanced; it
> now also asserts that the referenced pinned external buffer has refcnt == 1.
> 
> The description of RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE was updated to
> include the remaining requirements, which were missing here.
> 
> And finally:
> A new rte_mbuf_fast_free_bulk() inline function was added for the benefit of
> ethdev drivers supporting fast release of mbufs.
> It asserts these requirements and that the mbufs belong to the specified
> mempool, and then calls rte_mempool_put_bulk().
> 
> For symmetry, a new rte_mbuf_raw_alloc_bulk() inline function was also
> added.
> 
> Signed-off-by: Morten Brørup <mb@smartsharesystems.com>
> Acked-by: Dengdui Huang <huangdengdui@huawei.com>
> ---
> v2:
> * Fixed missing inline.
> v3:
> * Fixed missing experimental warning. (Stephen)
> * Added raw alloc bulk function.
> ---
>  lib/ethdev/rte_ethdev.h |  6 ++--
>  lib/mbuf/rte_mbuf.h     | 80 +++++++++++++++++++++++++++++++++++++++--
>  2 files changed, 82 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h index
> 1f71cad244..e9267fca79 100644
> --- a/lib/ethdev/rte_ethdev.h
> +++ b/lib/ethdev/rte_ethdev.h
> @@ -1612,8 +1612,10 @@ struct rte_eth_conf {
>  #define RTE_ETH_TX_OFFLOAD_MULTI_SEGS       RTE_BIT64(15)
>  /**
>   * Device supports optimization for fast release of mbufs.
> - * When set application must guarantee that per-queue all mbufs comes
> from
> - * the same mempool and has refcnt = 1.
> + * When set application must guarantee that per-queue all mbufs come
> + from the same mempool,
> + * are direct, have refcnt=1, next=NULL and nb_segs=1, as done by
> rte_pktmbuf_prefree_seg().
> + *
> + * @see rte_mbuf_fast_free_bulk()
>   */
>  #define RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE   RTE_BIT64(16)
>  #define RTE_ETH_TX_OFFLOAD_SECURITY         RTE_BIT64(17)
> diff --git a/lib/mbuf/rte_mbuf.h b/lib/mbuf/rte_mbuf.h index
> 0d2e0e64b3..1e40e7fcf7 100644
> --- a/lib/mbuf/rte_mbuf.h
> +++ b/lib/mbuf/rte_mbuf.h
> @@ -568,6 +568,10 @@ __rte_mbuf_raw_sanity_check(__rte_unused const
> struct rte_mbuf *m)
>  	RTE_ASSERT(rte_mbuf_refcnt_read(m) == 1);
>  	RTE_ASSERT(m->next == NULL);
>  	RTE_ASSERT(m->nb_segs == 1);
> +	RTE_ASSERT(!RTE_MBUF_CLONED(m));
> +	RTE_ASSERT(!RTE_MBUF_HAS_EXTBUF(m) ||
> +			(RTE_MBUF_HAS_PINNED_EXTBUF(m) &&
> +			rte_mbuf_ext_refcnt_read(m->shinfo) == 1));
>  	__rte_mbuf_sanity_check(m, 0);
>  }
> 
> @@ -606,6 +610,43 @@ static inline struct rte_mbuf
> *rte_mbuf_raw_alloc(struct rte_mempool *mp)
>  	return ret.m;
>  }
> 
> +/**
> + * @warning
> + * @b EXPERIMENTAL: This API may change, or be removed, without prior
> notice.
> + *
> + * Allocate a bulk of uninitialized mbufs from mempool *mp*.
> + *
> + * This function can be used by PMDs (especially in RX functions) to
> + * allocate a bulk of uninitialized mbufs. The driver is responsible of
> + * initializing all the required fields. See rte_pktmbuf_reset().
> + * For standard needs, prefer rte_pktmbuf_alloc_bulk().
> + *
> + * The caller can expect that the following fields of the mbuf
> +structure
> + * are initialized: buf_addr, buf_iova, buf_len, refcnt=1, nb_segs=1,
> + * next=NULL, pool, priv_size. The other fields must be initialized
> + * by the caller.
> + *
> + * @param mp
> + *   The mempool from which mbufs are allocated.
> + * @param mbufs
> + *   Array of pointers to mbufs.
> + * @param count
> + *   Array size.
> + * @return
> + *   - 0: Success.
> + *   - -ENOENT: Not enough entries in the mempool; no mbufs are retrieved.
> + */
> +__rte_experimental
> +static __rte_always_inline int
> +rte_mbuf_raw_alloc_bulk(struct rte_mempool *mp, struct rte_mbuf
> +**mbufs, unsigned int count) {
> +	int rc = rte_mempool_get_bulk(mp, (void **)mbufs, count);
> +	if (likely(rc == 0))
> +		for (unsigned int idx = 0; idx < count; idx++)
> +			__rte_mbuf_raw_sanity_check(mbufs[idx]);
> +	return rc;
> +}
> +
>  /**
>   * Put mbuf back into its original mempool.
>   *
> @@ -623,12 +664,47 @@ static inline struct rte_mbuf
> *rte_mbuf_raw_alloc(struct rte_mempool *mp)  static __rte_always_inline
> void  rte_mbuf_raw_free(struct rte_mbuf *m)  {
> -	RTE_ASSERT(!RTE_MBUF_CLONED(m) &&
> -		  (!RTE_MBUF_HAS_EXTBUF(m) ||
> RTE_MBUF_HAS_PINNED_EXTBUF(m)));
>  	__rte_mbuf_raw_sanity_check(m);
>  	rte_mempool_put(m->pool, m);
>  }
> 
> +/**
> + * @warning
> + * @b EXPERIMENTAL: This API may change, or be removed, without prior
> notice.
> + *
> + * Put a bulk of mbufs allocated from the same mempool back into the
> mempool.
> + *
> + * The caller must ensure that the mbufs come from the specified
> +mempool,
> + * are direct and properly reinitialized (refcnt=1, next=NULL,
> +nb_segs=1), as done by
> + * rte_pktmbuf_prefree_seg().
> + *
> + * This function should be used with care, when optimization is
> + * required. For standard needs, prefer rte_pktmbuf_free_bulk().
> + *
> + * @see RTE_ETH_TX_OFFLOAD_MBUF_FAST_FREE
> + *
> + * @param mp
> + *   The mempool to which the mbufs belong.
> + * @param mbufs
> + *   Array of pointers to packet mbufs.
> + *   The array must not contain NULL pointers.
> + * @param count
> + *   Array size.
> + */
> +__rte_experimental
> +static __rte_always_inline void
> +rte_mbuf_fast_free_bulk(struct rte_mempool *mp, struct rte_mbuf
> +**mbufs, unsigned int count) {
> +	for (unsigned int idx = 0; idx < count; idx++) {
> +		const struct rte_mbuf *m = mbufs[idx];
> +		RTE_ASSERT(m != NULL);
> +		RTE_ASSERT(m->pool == mp);
> +		__rte_mbuf_raw_sanity_check(m);
> +	}
> +
> +	rte_mempool_put_bulk(mp, (void **)mbufs, count); }
> +
>  /**
>   * The packet mbuf constructor.
>   *
> --
> 2.43.0