Re: [dpdk-dev] [PATCH v3 2/4] mbuf: create packet pool with external memory buffers

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

On Tue, Jan 14, 2020 at 09:15:03AM +0000, Viacheslav Ovsiienko wrote:
> The dedicated routine rte_pktmbuf_pool_create_extbuf() is
> provided to create mbuf pool with data buffers located in
> the pinned external memory. The application provides the
> external memory description and routine initialises each
> mbuf with appropriate virtual and physical buffer address.
> It is entirely application responsibility to register
> external memory with rte_extmem_register() API, map this
> memory, etc.
> 
> The new introduced flag RTE_PKTMBUF_POOL_F_PINNED_EXT_BUF
> is set in private pool structure, specifying the new special
> pool type. The allocated mbufs from pool of this kind will
> have the EXT_ATTACHED_MBUF flag set and NULL shared info
> pointer, because external buffers are not supposed to be
> freed and sharing management is not needed. Also, these
> mbufs can not be attached to other mbufs (not intended to
> be indirect).
> 
> Signed-off-by: Viacheslav Ovsiienko <viacheslavo@mellanox.com>
> ---
>  lib/librte_mbuf/rte_mbuf.c           | 144 ++++++++++++++++++++++++++++++++++-
>  lib/librte_mbuf/rte_mbuf.h           |  86 ++++++++++++++++++++-
>  lib/librte_mbuf/rte_mbuf_version.map |   1 +
>  3 files changed, 228 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
> index 8fa7f49..d151469 100644
> --- a/lib/librte_mbuf/rte_mbuf.c
> +++ b/lib/librte_mbuf/rte_mbuf.c
> @@ -59,9 +59,9 @@
>  	}
>  
>  	RTE_ASSERT(mp->elt_size >= sizeof(struct rte_mbuf) +
> -		user_mbp_priv->mbuf_data_room_size +
> +		((user_mbp_priv->flags & RTE_PKTMBUF_POOL_F_PINNED_EXT_BUF) ?
> +		0 : user_mbp_priv->mbuf_data_room_size) +
>  		user_mbp_priv->mbuf_priv_size);

Is this check really needed?

> -	RTE_ASSERT(user_mbp_priv->flags == 0);

We can keep
 RTE_ASSERT(user_mbp_priv->flags & ~RTE_PKTMBUF_POOL_F_PINNED_EXT_BUF == 0);

>  
>  	mbp_priv = rte_mempool_get_priv(mp);
>  	memcpy(mbp_priv, user_mbp_priv, sizeof(*mbp_priv));
> @@ -107,6 +107,63 @@
>  	m->next = NULL;
>  }
>  
> +/*
> + * pktmbuf constructor for the pool with pinned external buffer,
> + * given as a callback function to rte_mempool_obj_iter() in
> + * rte_pktmbuf_pool_create_extbuf(). Set the fields of a packet
> + * mbuf to their default values.
> + */
> +void
> +rte_pktmbuf_init_extmem(struct rte_mempool *mp,
> +			void *opaque_arg,
> +			void *_m,
> +			__attribute__((unused)) unsigned int i)
> +{
> +	struct rte_mbuf *m = _m;
> +	struct rte_pktmbuf_extmem_init_ctx *ctx = opaque_arg;
> +	struct rte_pktmbuf_extmem *ext_mem;
> +	uint32_t mbuf_size, buf_len, priv_size;
> +
> +	priv_size = rte_pktmbuf_priv_size(mp);
> +	mbuf_size = sizeof(struct rte_mbuf) + priv_size;
> +	buf_len = rte_pktmbuf_data_room_size(mp);
> +
> +	RTE_ASSERT(RTE_ALIGN(priv_size, RTE_MBUF_PRIV_ALIGN) == priv_size);
> +	RTE_ASSERT(mp->elt_size >= mbuf_size);
> +	RTE_ASSERT(buf_len <= UINT16_MAX);
> +
> +	memset(m, 0, mbuf_size);
> +	m->priv_size = priv_size;
> +	m->buf_len = (uint16_t)buf_len;
> +
> +	/* set the data buffer pointers to external memory */
> +	ext_mem = ctx->ext_mem + ctx->ext;
> +
> +	RTE_ASSERT(ctx->ext < ctx->ext_num);
> +	RTE_ASSERT(ctx->off < ext_mem->buf_len);
> +
> +	m->buf_addr = RTE_PTR_ADD(ext_mem->buf_ptr, ctx->off);
> +	m->buf_iova = ext_mem->buf_iova == RTE_BAD_IOVA ?
> +		      RTE_BAD_IOVA : (ext_mem->buf_iova + ctx->off);
> +
> +	ctx->off += ext_mem->elt_size;
> +	if (ctx->off >= ext_mem->buf_len) {
> +		ctx->off = 0;
> +		++ctx->ext;
> +	}
> +	/* keep some headroom between start of buffer and data */
> +	m->data_off = RTE_MIN(RTE_PKTMBUF_HEADROOM, (uint16_t)m->buf_len);
> +
> +	/* init some constant fields */
> +	m->pool = mp;
> +	m->nb_segs = 1;
> +	m->port = MBUF_INVALID_PORT;
> +	m->ol_flags = EXT_ATTACHED_MBUF;
> +	rte_mbuf_refcnt_set(m, 1);
> +	m->next = NULL;
> +}
> +
> +
>  /* Helper to create a mbuf pool with given mempool ops name*/
>  struct rte_mempool *
>  rte_pktmbuf_pool_create_by_ops(const char *name, unsigned int n,
> @@ -169,6 +226,89 @@ struct rte_mempool *
>  			data_room_size, socket_id, NULL);
>  }
>  
> +/* Helper to create a mbuf pool with pinned external data buffers. */
> +struct rte_mempool *
> +rte_pktmbuf_pool_create_extbuf(const char *name, unsigned int n,
> +	unsigned int cache_size, uint16_t priv_size,
> +	uint16_t data_room_size, int socket_id,
> +	struct rte_pktmbuf_extmem *ext_mem, unsigned int ext_num)
> +{
> +	struct rte_mempool *mp;
> +	struct rte_pktmbuf_pool_private mbp_priv;
> +	struct rte_pktmbuf_extmem_init_ctx init_ctx;
> +	const char *mp_ops_name;
> +	unsigned int elt_size;
> +	unsigned int i, n_elts = 0;
> +	int ret;
> +
> +	if (RTE_ALIGN(priv_size, RTE_MBUF_PRIV_ALIGN) != priv_size) {
> +		RTE_LOG(ERR, MBUF, "mbuf priv_size=%u is not aligned\n",
> +			priv_size);
> +		rte_errno = EINVAL;
> +		return NULL;
> +	}
> +	/* Check the external memory descriptors. */
> +	for (i = 0; i < ext_num; i++) {
> +		struct rte_pktmbuf_extmem *extm = ext_mem + i;
> +
> +		if (!extm->elt_size || !extm->buf_len || !extm->buf_ptr) {
> +			RTE_LOG(ERR, MBUF, "invalid extmem descriptor\n");
> +			rte_errno = EINVAL;
> +			return NULL;
> +		}
> +		if (data_room_size > extm->elt_size) {
> +			RTE_LOG(ERR, MBUF, "ext elt_size=%u is too small\n",
> +				priv_size);
> +			rte_errno = EINVAL;
> +			return NULL;
> +		}
> +		n_elts += extm->buf_len / extm->elt_size;
> +	}
> +	/* Check whether enough external memory provided. */
> +	if (n_elts < n) {
> +		RTE_LOG(ERR, MBUF, "not enough extmem\n");
> +		rte_errno = ENOMEM;
> +		return NULL;
> +	}
> +	elt_size = sizeof(struct rte_mbuf) + (unsigned int)priv_size;
> +	memset(&mbp_priv, 0, sizeof(mbp_priv));
> +	mbp_priv.mbuf_data_room_size = data_room_size;
> +	mbp_priv.mbuf_priv_size = priv_size;
> +	mbp_priv.flags = RTE_PKTMBUF_POOL_F_PINNED_EXT_BUF;
> +
> +	mp = rte_mempool_create_empty(name, n, elt_size, cache_size,
> +		 sizeof(struct rte_pktmbuf_pool_private), socket_id, 0);
> +	if (mp == NULL)
> +		return NULL;
> +
> +	mp_ops_name = rte_mbuf_best_mempool_ops();
> +	ret = rte_mempool_set_ops_byname(mp, mp_ops_name, NULL);
> +	if (ret != 0) {
> +		RTE_LOG(ERR, MBUF, "error setting mempool handler\n");
> +		rte_mempool_free(mp);
> +		rte_errno = -ret;
> +		return NULL;
> +	}
> +	rte_pktmbuf_pool_init(mp, &mbp_priv);
> +
> +	ret = rte_mempool_populate_default(mp);
> +	if (ret < 0) {
> +		rte_mempool_free(mp);
> +		rte_errno = -ret;
> +		return NULL;
> +	}
> +
> +	init_ctx = (struct rte_pktmbuf_extmem_init_ctx){
> +		.ext_mem = ext_mem,
> +		.ext_num = ext_num,
> +		.ext = 0,
> +		.off = 0,
> +	};
> +	rte_mempool_obj_iter(mp, rte_pktmbuf_init_extmem, &init_ctx);
> +
> +	return mp;
> +}

Instead of duplicating some code, would it be possible to do:

int
rte_pktmbuf_pool_attach_extbuf(struct rte_mempool *mp,
	struct rte_pktmbuf_extmem *ext_mem, unsigned int ext_num)
{
	struct rte_pktmbuf_extmem_init_ctx init_ctx = { 0 };
	struct rte_pktmbuf_pool_private *priv;

	/* XXX assert mempool is fully populated? */

	priv = rte_mempool_get_priv(mp);
	mbp_priv.flags |= RTE_PKTMBUF_POOL_F_PINNED_EXT_BUF;

	rte_mempool_obj_iter(mp, rte_pktmbuf_init_extmem, &init_ctx);

	return init_ctx.ret;
}

The application would have to call:

	rte_pktmbuf_pool_create(...);
	rte_pktmbuf_pool_attach_extbuf(...);


> +
>  /* do some sanity checks on a mbuf: panic if it fails */
>  void
>  rte_mbuf_sanity_check(const struct rte_mbuf *m, int is_header)
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 8f486af..7bde297 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -642,6 +642,34 @@ static inline struct rte_mbuf *rte_mbuf_raw_alloc(struct rte_mempool *mp)
>  void rte_pktmbuf_init(struct rte_mempool *mp, void *opaque_arg,
>  		      void *m, unsigned i);
>  
> +/** The context to initialize the mbufs with pinned external buffers. */
> +struct rte_pktmbuf_extmem_init_ctx {
> +	struct rte_pktmbuf_extmem *ext_mem; /* pointer to descriptor array. */
> +	unsigned int ext_num; /* number of descriptors in array. */
> +	unsigned int ext; /* loop descriptor index. */
> +	size_t off; /* loop buffer offset. */
> +};
> +
> +/**
> + * The packet mbuf constructor for pools with pinned external memory.
> + *
> + * This function initializes some fields in the mbuf structure that are
> + * not modified by the user once created (origin pool, buffer start
> + * address, and so on). This function is given as a callback function to
> + * rte_mempool_obj_iter() called from rte_mempool_create_extmem().
> + *
> + * @param mp
> + *   The mempool from which mbufs originate.
> + * @param opaque_arg
> + *   A pointer to the rte_pktmbuf_extmem_init_ctx - initialization
> + *   context structure
> + * @param m
> + *   The mbuf to initialize.
> + * @param i
> + *   The index of the mbuf in the pool table.
> + */
> +void rte_pktmbuf_init_extmem(struct rte_mempool *mp, void *opaque_arg,
> +			     void *m, unsigned int i);
>  
>  /**
>   * A  packet mbuf pool constructor.
> @@ -743,6 +771,62 @@ struct rte_mempool *
>  	unsigned int cache_size, uint16_t priv_size, uint16_t data_room_size,
>  	int socket_id, const char *ops_name);
>  
> +/** A structure that describes the pinned external buffer segment. */
> +struct rte_pktmbuf_extmem {
> +	void *buf_ptr;		/**< The virtual address of data buffer. */
> +	rte_iova_t buf_iova;	/**< The IO address of the data buffer. */
> +	size_t buf_len;		/**< External buffer length in bytes. */
> +	uint16_t elt_size;	/**< mbuf element size in bytes. */
> +};
> +
> +/**
> + * Create a mbuf pool with external pinned data buffers.
> + *
> + * This function creates and initializes a packet mbuf pool that contains
> + * only mbufs with external buffer. It is a wrapper to rte_mempool functions.
> + *
> + * @param name
> + *   The name of the mbuf pool.
> + * @param n
> + *   The number of elements in the mbuf pool. The optimum size (in terms
> + *   of memory usage) for a mempool is when n is a power of two minus one:
> + *   n = (2^q - 1).
> + * @param cache_size
> + *   Size of the per-core object cache. See rte_mempool_create() for
> + *   details.
> + * @param priv_size
> + *   Size of application private are between the rte_mbuf structure
> + *   and the data buffer. This value must be aligned to RTE_MBUF_PRIV_ALIGN.
> + * @param data_room_size
> + *   Size of data buffer in each mbuf, including RTE_PKTMBUF_HEADROOM.
> + * @param socket_id
> + *   The socket identifier where the memory should be allocated. The
> + *   value can be *SOCKET_ID_ANY* if there is no NUMA constraint for the
> + *   reserved zone.
> + * @param ext_mem
> + *   Pointer to the array of structures describing the external memory
> + *   for data buffers. It is caller responsibility to register this memory
> + *   with rte_extmem_register() (if needed), map this memory to appropriate
> + *   physical device, etc.
> + * @param ext_num
> + *   Number of elements in the ext_mem array.
> + * @return
> + *   The pointer to the new allocated mempool, on success. NULL on error
> + *   with rte_errno set appropriately. Possible rte_errno values include:
> + *    - E_RTE_NO_CONFIG - function could not get pointer to rte_config structure
> + *    - E_RTE_SECONDARY - function was called from a secondary process instance
> + *    - EINVAL - cache size provided is too large, or priv_size is not aligned.
> + *    - ENOSPC - the maximum number of memzones has already been allocated
> + *    - EEXIST - a memzone with the same name already exists
> + *    - ENOMEM - no appropriate memory area found in which to create memzone
> + */
> +__rte_experimental
> +struct rte_mempool *
> +rte_pktmbuf_pool_create_extbuf(const char *name, unsigned int n,
> +	unsigned int cache_size, uint16_t priv_size,
> +	uint16_t data_room_size, int socket_id,
> +	struct rte_pktmbuf_extmem *ext_mem, unsigned int ext_num);
> +
>  /**
>   * Get the data room size of mbufs stored in a pktmbuf_pool
>   *
> @@ -818,7 +902,7 @@ static inline void rte_pktmbuf_reset(struct rte_mbuf *m)
>  	m->nb_segs = 1;
>  	m->port = MBUF_INVALID_PORT;
>  
> -	m->ol_flags = 0;
> +	m->ol_flags &= EXT_ATTACHED_MBUF;
>  	m->packet_type = 0;
>  	rte_pktmbuf_reset_headroom(m);
>  

I wonder if it should go in previous patch?

> diff --git a/lib/librte_mbuf/rte_mbuf_version.map b/lib/librte_mbuf/rte_mbuf_version.map
> index 3bbb476..ab161bc 100644
> --- a/lib/librte_mbuf/rte_mbuf_version.map
> +++ b/lib/librte_mbuf/rte_mbuf_version.map
> @@ -44,5 +44,6 @@ EXPERIMENTAL {
>  	rte_mbuf_dyn_dump;
>  	rte_pktmbuf_copy;
>  	rte_pktmbuf_free_bulk;
> +	rte_pktmbuf_pool_create_extbuf;
>  
>  };
> -- 
> 1.8.3.1
>