[dpdk-dev] [PATCH v8 1/6] ethdev: introduce Rx buffer split
Andrew Rybchenko
arybchenko at solarflare.com
Fri Oct 16 10:58:16 CEST 2020
On 10/16/20 11:51 AM, Andrew Rybchenko wrote:
> On 10/16/20 10:48 AM, Viacheslav Ovsiienko wrote:
>> The DPDK datapath in the transmit direction is very flexible.
>> An application can build the multi-segment packet and manages
>> almost all data aspects - the memory pools where segments
>> are allocated from, the segment lengths, the memory attributes
>> like external buffers, registered for DMA, etc.
>>
>> In the receiving direction, the datapath is much less flexible,
>> an application can only specify the memory pool to configure the
>> receiving queue and nothing more. In order to extend receiving
>> datapath capabilities it is proposed to add the way to provide
>> extended information how to split the packets being received.
>>
>> The new offload flag RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT in device
>> capabilities is introduced to present the way for PMD to report to
>> application about supporting Rx packet split to configurable
>> segments. Prior invoking the rte_eth_rx_queue_setup() routine
>> application should check RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT flag.
>>
>> The following structure is introduced to specify the Rx packet
>> segment for RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT offload:
>>
>> struct rte_eth_rxseg_split {
>>
>> struct rte_mempool *mp; /* memory pools to allocate segment from */
>> uint16_t length; /* segment maximal data length,
>> configures "split point" */
>> uint16_t offset; /* data offset from beginning
>> of mbuf data buffer */
>> uint32_t reserved; /* reserved field */
>> };
>>
>> The segment descriptions are added to the rte_eth_rxconf structure:
>> rx_seg - pointer the array of segment descriptions, each element
>> describes the memory pool, maximal data length, initial
>> data offset from the beginning of data buffer in mbuf.
>> This array allows to specify the different settings for
>> each segment in individual fashion.
>> rx_nseg - number of elements in the array
>>
>> If the extended segment descriptions is provided with these new
>> fields the mp parameter of the rte_eth_rx_queue_setup must be
>> specified as NULL to avoid ambiguity.
>>
>> There are two options to specify Rx buffer configuration:
>> - mp is not NULL, rx_conf.rx_seg is NULL, rx_conf.rx_nseg is zero,
>> it is compatible configuration, follows existing implementation,
>> provides single pool and no description for segment sizes
>> and offsets.
>> - mp is NULL, rx_conf.rx_seg is not NULL, rx_conf.rx_nseg is not
>> zero, it provides the extended configuration, individually for
>> each segment.
>>
>> f the Rx queue is configured with new settings the packets being
>> received will be split into multiple segments pushed to the mbufs
>> with specified attributes. The PMD will split the received packets
>> into multiple segments according to the specification in the
>> description array.
>>
>> For example, let's suppose we configured the Rx queue with the
>> following segments:
>> seg0 - pool0, len0=14B, off0=2
>> seg1 - pool1, len1=20B, off1=128B
>> seg2 - pool2, len2=20B, off2=0B
>> seg3 - pool3, len3=512B, off3=0B
>>
>> The packet 46 bytes long will look like the following:
>> seg0 - 14B long @ RTE_PKTMBUF_HEADROOM + 2 in mbuf from pool0
>> seg1 - 20B long @ 128 in mbuf from pool1
>> seg2 - 12B long @ 0 in mbuf from pool2
>>
>> The packet 1500 bytes long will look like the following:
>> seg0 - 14B @ RTE_PKTMBUF_HEADROOM + 2 in mbuf from pool0
>> seg1 - 20B @ 128 in mbuf from pool1
>> seg2 - 20B @ 0 in mbuf from pool2
>> seg3 - 512B @ 0 in mbuf from pool3
>> seg4 - 512B @ 0 in mbuf from pool3
>> seg5 - 422B @ 0 in mbuf from pool3
>>
>> The offload RTE_ETH_RX_OFFLOAD_SCATTER must be present and
>> configured to support new buffer split feature (if rx_nseg
>> is greater than one).
>>
>> The split limitations imposed by underlying PMD is reported
>> in the new introduced rte_eth_dev_info->rx_seg_capa field.
>>
>> The new approach would allow splitting the ingress packets into
>> multiple parts pushed to the memory with different attributes.
>> For example, the packet headers can be pushed to the embedded
>> data buffers within mbufs and the application data into
>> the external buffers attached to mbufs allocated from the
>> different memory pools. The memory attributes for the split
>> parts may differ either - for example the application data
>> may be pushed into the external memory located on the dedicated
>> physical device, say GPU or NVMe. This would improve the DPDK
>> receiving datapath flexibility with preserving compatibility
>> with existing API.
>>
>> Signed-off-by: Viacheslav Ovsiienko <viacheslavo at nvidia.com>
>> Acked-by: Ajit Khaparde <ajit.khaparde at broadcom.com>
>> Acked-by: Jerin Jacob <jerinj at marvell.com>
With below review notes processed:
Reviewed-by: Andrew Rybchenko <andrew.rybchenko at oktetlabs.ru>
>> ---
>> doc/guides/nics/features.rst | 15 ++++
>> doc/guides/rel_notes/deprecation.rst | 5 --
>> doc/guides/rel_notes/release_20_11.rst | 9 ++
>> lib/librte_ethdev/rte_ethdev.c | 152 +++++++++++++++++++++++++++------
>> lib/librte_ethdev/rte_ethdev.h | 88 ++++++++++++++++++-
>> 5 files changed, 238 insertions(+), 31 deletions(-)
>>
>> diff --git a/doc/guides/nics/features.rst b/doc/guides/nics/features.rst
>> index dd8c955..832ea3b 100644
>> --- a/doc/guides/nics/features.rst
>> +++ b/doc/guides/nics/features.rst
>> @@ -185,6 +185,21 @@ Supports receiving segmented mbufs.
>> * **[related] eth_dev_ops**: ``rx_pkt_burst``.
>>
>>
>> +.. _nic_features_buffer_split:
>> +
>> +Buffer Split on Rx
>> +------------------
>> +
>> +Scatters the packets being received on specified boundaries to segmented mbufs.
>> +
>> +* **[uses] rte_eth_rxconf,rte_eth_rxmode**: ``offloads:RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT``.
>> +* **[uses] rte_eth_rxconf**: ``rx_conf.rx_seg, rx_conf.rx_nseg``.
>> +* **[implements] datapath**: ``Buffer Split functionality``.
>> +* **[provides] rte_eth_dev_info**: ``rx_offload_capa:RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT``.
>> +* **[provides] eth_dev_ops**: ``rxq_info_get:buffer_split``.
>> +* **[related] API**: ``rte_eth_rx_queue_setup()``.
>> +
>> +
>> .. _nic_features_lro:
>>
>> LRO
>> diff --git a/doc/guides/rel_notes/deprecation.rst b/doc/guides/rel_notes/deprecation.rst
>> index 584e720..232cd54 100644
>> --- a/doc/guides/rel_notes/deprecation.rst
>> +++ b/doc/guides/rel_notes/deprecation.rst
>> @@ -138,11 +138,6 @@ Deprecation Notices
>> In 19.11 PMDs will still update the field even when the offload is not
>> enabled.
>>
>> -* ethdev: Add new fields to ``rte_eth_rxconf`` to configure the receiving
>> - queues to split ingress packets into multiple segments according to the
>> - specified lengths into the buffers allocated from the specified
>> - memory pools. The backward compatibility to existing API is preserved.
>> -
>> * ethdev: ``rx_descriptor_done`` dev_ops and ``rte_eth_rx_descriptor_done``
>> will be removed in 21.11.
>> Existing ``rte_eth_rx_descriptor_status`` and ``rte_eth_tx_descriptor_status``
>> diff --git a/doc/guides/rel_notes/release_20_11.rst b/doc/guides/rel_notes/release_20_11.rst
>> index bcc0fc2..bcc2479 100644
>> --- a/doc/guides/rel_notes/release_20_11.rst
>> +++ b/doc/guides/rel_notes/release_20_11.rst
>> @@ -60,6 +60,12 @@ New Features
>> Added the FEC API which provides functions for query FEC capabilities and
>> current FEC mode from device. Also, API for configuring FEC mode is also provided.
>>
>> +* **Introduced extended buffer description for receiving.**
>> +
>> + Added the extended Rx buffer description for Rx queue setup routine
>> + providing the individual settings for each Rx segment with maximal size,
>> + buffer offset and memory pool to allocate data buffers from.
>> +
>> * **Updated Broadcom bnxt driver.**
>>
>> Updated the Broadcom bnxt driver with new features and improvements, including:
>> @@ -253,6 +259,9 @@ API Changes
>> As the data of ``uint8_t`` will be truncated when queue number under
>> a TC is greater than 256.
>>
>> +* ethdev: Added fields rx_seg and rx_nseg to rte_eth_rxconf structure
>> + to provide extended description of the receiving buffer.
>> +
>> * vhost: Moved vDPA APIs from experimental to stable.
>>
>> * rawdev: Added a structure size parameter to the functions
>> diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
>> index 892c246..0eda3f4 100644
>> --- a/lib/librte_ethdev/rte_ethdev.c
>> +++ b/lib/librte_ethdev/rte_ethdev.c
>> @@ -105,6 +105,9 @@ struct rte_eth_xstats_name_off {
>> #define RTE_RX_OFFLOAD_BIT2STR(_name) \
>> { DEV_RX_OFFLOAD_##_name, #_name }
>>
>> +#define RTE_ETH_RX_OFFLOAD_BIT2STR(_name) \
>> + { RTE_ETH_RX_OFFLOAD_##_name, #_name }
>> +
>> static const struct {
>> uint64_t offload;
>> const char *name;
>> @@ -128,9 +131,11 @@ struct rte_eth_xstats_name_off {
>> RTE_RX_OFFLOAD_BIT2STR(SCTP_CKSUM),
>> RTE_RX_OFFLOAD_BIT2STR(OUTER_UDP_CKSUM),
>> RTE_RX_OFFLOAD_BIT2STR(RSS_HASH),
>> + RTE_ETH_RX_OFFLOAD_BIT2STR(BUFFER_SPLIT),
>> };
>>
>> #undef RTE_RX_OFFLOAD_BIT2STR
>> +#undef RTE_ETH_RX_OFFLOAD_BIT2STR
>>
>> #define RTE_TX_OFFLOAD_BIT2STR(_name) \
>> { DEV_TX_OFFLOAD_##_name, #_name }
>> @@ -1763,6 +1768,77 @@ struct rte_eth_dev *
>> return ret;
>> }
>>
>> +static int
>> +rte_eth_rx_queue_check_split(const struct rte_eth_rxseg *rx_seg,
>> + uint16_t n_seg, uint32_t *mbp_buf_size,
>> + const struct rte_eth_dev_info *dev_info)
>> +{
>> + const struct rte_eth_rxseg_capa *seg_capa = &dev_info->rx_seg_capa;
>> + struct rte_mempool *mp_first;
>> + uint32_t offset_mask;
>> + uint16_t seg_idx;
>> +
>> + if (n_seg > seg_capa->max_seg) {
>> + RTE_ETHDEV_LOG(ERR,
>> + "Requested Rx segments %u exceed supported %u\n",
>> + n_seg, seg_capa->max_seg);
>> + return -EINVAL;
>> + }
>> + /*
>> + * Check the sizes and offsets against buffer sizes
>> + * for each segment specified in extended configuration.
>> + */
>> + mp_first = rx_seg[0].conf.split.mp;
>> + offset_mask = (1u << seg_capa->offset_align_log2) - 1;
>> + for (seg_idx = 0; seg_idx < n_seg; seg_idx++) {
>> + struct rte_mempool *mpl = rx_seg[seg_idx].conf.split.mp;
>> + uint32_t length = rx_seg[seg_idx].conf.split.length;
>> + uint32_t offset = rx_seg[seg_idx].conf.split.offset;
>> +
>> + if (mpl == NULL) {
>> + RTE_ETHDEV_LOG(ERR, "null mempool pointer\n");
>> + return -EINVAL;
>> + }
>> + if (seg_idx != 0 && mp_first != mpl &&
>> + seg_capa->multi_pools == 0) {
>> + RTE_ETHDEV_LOG(ERR, "Receiving to multiple pools is not supported\n");
>> + return -ENOTSUP;
>> + }
>> + if (offset != 0) {
>> + if (seg_capa->offset_allowed == 0) {
>> + RTE_ETHDEV_LOG(ERR, "Rx segmentation with offset is not supported\n");
>> + return -ENOTSUP;
>> + }
>> + if (offset & offset_mask) {
>> + RTE_ETHDEV_LOG(ERR, "Rx segmentat invalid offset alignment %u, %u\n",
>> + offset,
>> + seg_capa->offset_align_log2);
>> + return -EINVAL;
>> + }
>> + }
>> + if (mpl->private_data_size <
>> + sizeof(struct rte_pktmbuf_pool_private)) {
>> + RTE_ETHDEV_LOG(ERR,
>> + "%s private_data_size %u < %u\n",
>> + mpl->name, mpl->private_data_size,
>> + (unsigned int)sizeof
>> + (struct rte_pktmbuf_pool_private));
>> + return -ENOSPC;
>> + }
>> + offset += seg_idx != 0 ? 0 : RTE_PKTMBUF_HEADROOM;
>> + *mbp_buf_size = rte_pktmbuf_data_room_size(mpl);
>> + length = length != 0 ? length : *mbp_buf_size;
>> + if (*mbp_buf_size < length + offset) {
>> + RTE_ETHDEV_LOG(ERR,
>> + "%s mbuf_data_room_size %u < %u (segment length=%u + segment offset=%u)\n",
>> + mpl->name, *mbp_buf_size,
>> + length + offset, length, offset);
>> + return -EINVAL;
>> + }
>> + }
>> + return 0;
>> +}
>> +
>> int
>> rte_eth_rx_queue_setup(uint16_t port_id, uint16_t rx_queue_id,
>> uint16_t nb_rx_desc, unsigned int socket_id,
>> @@ -1784,38 +1860,64 @@ struct rte_eth_dev *
>> return -EINVAL;
>> }
>>
>> - if (mp == NULL) {
>> - RTE_ETHDEV_LOG(ERR, "Invalid null mempool pointer\n");
>> - return -EINVAL;
>> - }
>> -
>> RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->rx_queue_setup, -ENOTSUP);
>>
>> - /*
>> - * Check the size of the mbuf data buffer.
>> - * This value must be provided in the private data of the memory pool.
>> - * First check that the memory pool has a valid private data.
>> - */
>> ret = rte_eth_dev_info_get(port_id, &dev_info);
>> if (ret != 0)
>> return ret;
>>
>> - if (mp->private_data_size < sizeof(struct rte_pktmbuf_pool_private)) {
>> - RTE_ETHDEV_LOG(ERR, "%s private_data_size %d < %d\n",
>> - mp->name, (int)mp->private_data_size,
>> - (int)sizeof(struct rte_pktmbuf_pool_private));
>> - return -ENOSPC;
>> - }
>> - mbp_buf_size = rte_pktmbuf_data_room_size(mp);
>> + if (mp != NULL) {
>> + /* Single pool configuration check. */
>> + if (rx_conf->rx_nseg != 0) {
>> + RTE_ETHDEV_LOG(ERR,
>> + "Ambiguous segment configuration\n");
>> + return -EINVAL;
>> + }
>> + /*
>> + * Check the size of the mbuf data buffer, this value
>> + * must be provided in the private data of the memory pool.
>> + * First check that the memory pool(s) has a valid private data.
>> + */
>> + if (mp->private_data_size <
>> + sizeof(struct rte_pktmbuf_pool_private)) {
>> + RTE_ETHDEV_LOG(ERR, "%s private_data_size %u < %u\n",
>> + mp->name, mp->private_data_size,
>> + (unsigned int)
>> + sizeof(struct rte_pktmbuf_pool_private));
>> + return -ENOSPC;
>> + }
>> + mbp_buf_size = rte_pktmbuf_data_room_size(mp);
>> + if (mbp_buf_size < dev_info.min_rx_bufsize +
>> + RTE_PKTMBUF_HEADROOM) {
>> + RTE_ETHDEV_LOG(ERR,
>> + "%s mbuf_data_room_size %u < %u (RTE_PKTMBUF_HEADROOM=%u + min_rx_bufsize(dev)=%u)\n",
>> + mp->name, mbp_buf_size,
>> + RTE_PKTMBUF_HEADROOM +
>> + dev_info.min_rx_bufsize,
>> + RTE_PKTMBUF_HEADROOM,
>> + dev_info.min_rx_bufsize);
>> + return -EINVAL;
>> + }
>> + } else {
>> + const struct rte_eth_rxseg *rx_seg = rx_conf->rx_seg;
>> + uint16_t n_seg = rx_conf->rx_nseg;
>>
>> - if (mbp_buf_size < dev_info.min_rx_bufsize + RTE_PKTMBUF_HEADROOM) {
>> - RTE_ETHDEV_LOG(ERR,
>> - "%s mbuf_data_room_size %d < %d (RTE_PKTMBUF_HEADROOM=%d + min_rx_bufsize(dev)=%d)\n",
>> - mp->name, (int)mbp_buf_size,
>> - (int)(RTE_PKTMBUF_HEADROOM + dev_info.min_rx_bufsize),
>> - (int)RTE_PKTMBUF_HEADROOM,
>> - (int)dev_info.min_rx_bufsize);
>> - return -EINVAL;
>> + /* Extended multi-segment configuration check. */
>> + if (rx_conf->rx_seg == NULL || rx_conf->rx_nseg == 0) {
>> + RTE_ETHDEV_LOG(ERR,
>> + "Memory pool is null and no extended configuration provided\n");
>> + return -EINVAL;
>> + }
>> + if (rx_conf->offloads & RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT) {
>> + ret = rte_eth_rx_queue_check_split(rx_seg, n_seg,
>> + &mbp_buf_size,
>> + &dev_info);
>> + if (ret != 0)
>> + return ret;
>> + } else {
>> + RTE_ETHDEV_LOG(ERR, "No Rx segmentation offload configured\n");
>> + return -EINVAL;
>> + }
>> }
>>
>> /* Use default specified by driver, if nb_rx_desc is zero */
>> diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
>> index 5bcfbb8..6f18bec 100644
>> --- a/lib/librte_ethdev/rte_ethdev.h
>> +++ b/lib/librte_ethdev/rte_ethdev.h
>> @@ -970,6 +970,27 @@ struct rte_eth_txmode {
>> };
>>
>> /**
>> + * A structure used to configure an Rx packet segment to split.
>> + */
>> +struct rte_eth_rxseg_split {
>> + struct rte_mempool *mp; /**< Memory pool to allocate segment from. */
>> + uint16_t length; /**< Segment data length, configures split point. */
>> + uint16_t offset; /**< Data offset from beginning of mbuf data buffer. */
>> + uint32_t reserved; /**< Reserved field. */
>> +};
>> +
>> +/**
>> + * A common structure used to describe Rx packet segment properties.
>> + */
>> +struct rte_eth_rxseg {
>> + union {
>
> Why not just 'union rte_eth_rxseg' ?
>
>> + /* The settings for buffer split offload. */
>> + struct rte_eth_rxseg_split split;
>
> Pointer to a split table must be here. I.e.
> struct rte_eth_rxseg_split *split;
> Also it must be specified how the array is terminated.
> We need either a number of define last item condition
> (mp == NULL ?)
>
>> + /* The other features settings should be added here. */
>> + } conf;
>> +};
>
>
>
>> +
>> +/**
>> * A structure used to configure an RX ring of an Ethernet port.
>> */
>> struct rte_eth_rxconf {
>> @@ -977,6 +998,46 @@ struct rte_eth_rxconf {
>> uint16_t rx_free_thresh; /**< Drives the freeing of RX descriptors. */
>> uint8_t rx_drop_en; /**< Drop packets if no descriptors are available. */
>> uint8_t rx_deferred_start; /**< Do not start queue with rte_eth_dev_start(). */
>> + uint16_t rx_nseg; /**< Number of descriptions in rx_seg array. */
>> + /**
>> + * Points to the array of segment descriptions. Each array element
>> + * describes the properties for each segment in the receiving
>> + * buffer according to feature descripting structure.
>> + *
>> + * The supported capabilities of receiving segmentation is reported
>> + * in rte_eth_dev_info ->rx_seg_capa field.
>> + *
>> + * If RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT flag is set in offloads field,
>> + * the PMD will split the received packets into multiple segments
>> + * according to the specification in the description array:
>> + *
>> + * - the first network buffer will be allocated from the memory pool,
>> + * specified in the first array element, the second buffer, from the
>> + * pool in the second element, and so on.
>> + *
>> + * - the offsets from the segment description elements specify
>> + * the data offset from the buffer beginning except the first mbuf.
>> + * For this one the offset is added with RTE_PKTMBUF_HEADROOM.
>> + *
>> + * - the lengths in the elements define the maximal data amount
>> + * being received to each segment. The receiving starts with filling
>> + * up the first mbuf data buffer up to specified length. If the
>> + * there are data remaining (packet is longer than buffer in the first
>> + * mbuf) the following data will be pushed to the next segment
>> + * up to its own length, and so on.
>> + *
>> + * - If the length in the segment description element is zero
>> + * the actual buffer size will be deduced from the appropriate
>> + * memory pool properties.
>> + *
>> + * - if there is not enough elements to describe the buffer for entire
>> + * packet of maximal length the following parameters will be used
>> + * for the all remaining segments:
>> + * - pool from the last valid element
>> + * - the buffer size from this pool
>> + * - zero offset
>> + */
>> + struct rte_eth_rxseg *rx_seg;
>
> It must not be a pointer. It looks really strange this way
> taking into account that it is a union in fact.
> Also, why is it put here in the middle of exsiting structure?
> IMHO it should be added after offlaods.
>
>> /**
>> * Per-queue Rx offloads to be set using DEV_RX_OFFLOAD_* flags.
>> * Only offloads set on rx_queue_offload_capa or rx_offload_capa
>> @@ -1260,6 +1321,7 @@ struct rte_eth_conf {
>> #define DEV_RX_OFFLOAD_SCTP_CKSUM 0x00020000
>> #define DEV_RX_OFFLOAD_OUTER_UDP_CKSUM 0x00040000
>> #define DEV_RX_OFFLOAD_RSS_HASH 0x00080000
>> +#define RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT 0x00100000
>>
>> #define DEV_RX_OFFLOAD_CHECKSUM (DEV_RX_OFFLOAD_IPV4_CKSUM | \
>> DEV_RX_OFFLOAD_UDP_CKSUM | \
>> @@ -1376,6 +1438,17 @@ struct rte_eth_switch_info {
>> };
>>
>> /**
>> + * Ethernet device Rx buffer segmentation capabilities.
>> + */
>> +__extension__
>> +struct rte_eth_rxseg_capa {
>> + uint16_t max_seg; /**< Maximum amount of segments to split. */
>
> May be 'max_segs' to avoid confusing vs maximum segment length.
>
>> + uint16_t multi_pools:1; /**< Supports receiving to multiple pools.*/
>> + uint16_t offset_allowed:1; /**< Supports buffer offsets. */
>> + uint16_t offset_align_log2:4; /**< Required offset alignment. */
>
> 4 bits are even insufficient to specify cache-line alignment.
> IMHO at least 8 bits are required.
>
> Consider to put 32 width bit-fields at start of the structure.
> Than, max_segs (16), offset_align_log2 (8), plus reserved (8).
>
>> +};
>> +
>> +/**
>> * Ethernet device information
>> */
>>
>> @@ -1403,6 +1476,7 @@ struct rte_eth_dev_info {
>> /** Maximum number of hash MAC addresses for MTA and UTA. */
>> uint16_t max_vfs; /**< Maximum number of VFs. */
>> uint16_t max_vmdq_pools; /**< Maximum number of VMDq pools. */
>> + struct rte_eth_rxseg_capa rx_seg_capa; /**< Segmentation capability.*/
>
> Why is it put in the middle of existing structure?
>
>> uint64_t rx_offload_capa;
>> /**< All RX offload capabilities including all per-queue ones */
>> uint64_t tx_offload_capa;
>> @@ -2027,9 +2101,21 @@ int rte_eth_dev_configure(uint16_t port_id, uint16_t nb_rx_queue,
>> * No need to repeat any bit in rx_conf->offloads which has already been
>> * enabled in rte_eth_dev_configure() at port level. An offloading enabled
>> * at port level can't be disabled at queue level.
>> + * The configuration structure also contains the pointer to the array
>> + * of the receiving buffer segment descriptions, see rx_seg and rx_nseg
>> + * fields, this extended configuration might be used by split offloads like
>> + * RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT. If mp_pool is not NULL,
>> + * the extended configuration fields must be set to NULL and zero.
>> * @param mb_pool
>> * The pointer to the memory pool from which to allocate *rte_mbuf* network
>> - * memory buffers to populate each descriptor of the receive ring.
>> + * memory buffers to populate each descriptor of the receive ring. There are
>> + * two options to provide Rx buffer configuration:
>> + * - single pool:
>> + * mb_pool is not NULL, rx_conf.rx_seg is NULL, rx_conf.rx_nseg is 0.
>> + * - multiple segments description:
>> + * mb_pool is NULL, rx_conf.rx_seg is not NULL, rx_conf.rx_nseg is not 0.
>> + * Taken only if flag RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT is set in offloads.
>> + *
>> * @return
>> * - 0: Success, receive queue correctly set up.
>> * - -EIO: if device is removed.
>>
>
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