RE: [RFC,v2 1/3] ethdev: introduce protocol type based header split

["Ding, Xuan" <xuan.ding@intel.com>]

Hi Qi,

> -----Original Message-----
> From: Zhang, Qi Z <qi.z.zhang@intel.com>
> Sent: Tuesday, March 22, 2022 3:14 PM
> To: Ding, Xuan <xuan.ding@intel.com>; thomas@monjalon.net; Yigit, Ferruh
> <ferruh.yigit@intel.com>; andrew.rybchenko@oktetlabs.ru
> Cc: dev@dpdk.org; stephen@networkplumber.org;
> mb@smartsharesystems.com; viacheslavo@nvidia.com; Yu, Ping
> <ping.yu@intel.com>; Wu, WenxuanX <wenxuanx.wu@intel.com>; Wang,
> YuanX <yuanx.wang@intel.com>
> Subject: RE: [RFC,v2 1/3] ethdev: introduce protocol type based header split
> 
> 
> 
> > -----Original Message-----
> > From: Ding, Xuan <xuan.ding@intel.com>
> > Sent: Tuesday, March 22, 2022 11:56 AM
> > To: thomas@monjalon.net; Yigit, Ferruh <ferruh.yigit@intel.com>;
> > andrew.rybchenko@oktetlabs.ru
> > Cc: dev@dpdk.org; stephen@networkplumber.org;
> > mb@smartsharesystems.com; viacheslavo@nvidia.com; Zhang, Qi Z
> > <qi.z.zhang@intel.com>; Yu, Ping <ping.yu@intel.com>; Wu, WenxuanX
> > <wenxuanx.wu@intel.com>; Ding, Xuan <xuan.ding@intel.com>; Wang,
> YuanX
> > <yuanx.wang@intel.com>
> > Subject: [RFC,v2 1/3] ethdev: introduce protocol type based header
> > split
> >
> > From: Xuan Ding <xuan.ding@intel.com>
> >
> > Header split consists of splitting a received packet into two separate
> > regions based on the packet content. The split happens after the
> > packet header and before the packet payload. Splitting is usually
> > between the packet header that can be posted to a dedicated buffer and
> > the packet payload that can be posted to a different buffer.
> >
> > Currently, Rx buffer split supports length and offset based packet split.
> > Although header split is a subset of buffer split, configure buffer
> > split based on length and offset is not suitable for NICs that do
> > split based on header protocol types. And tunneling makes the
> > conversion from offset to protocol impossible.
> >
> > This patch extends the current buffer split to support protocol based
> > header split. A new proto field is introduced in the
> > rte_eth_rxseg_split structure reserved field to specify header
> > protocol type. With Rx offload flag RTE_ETH_RX_OFFLOAD_HEADER_SPLIT
> > enabled and protocol type configured, PMD will split the ingress packets
> into two separate regions.
> > Currently, both inner and outer L2/L3/L4 level header split can be
> supported.
> >
> > For example, let's suppose we configured the Rx queue with the
> > following
> > segments:
> >     seg0 - pool0
> >     seg1 - pool1
> >
> > With header split type configured with RTE_ETH_RX_HEADER_SPLIT_UDP,
> > the packet consists of MAC_IP_UDP_PAYLOAD will be split like following:
> >     seg0 - pool0, udp_header
> >     seg1 - pool1, payload
> >
> > The memory attributes for the split parts may differ either - for
> > example the
> > mempool0 and mempool1 belong to dpdk memory and external memory,
> > respectively.
> >
> > Signed-off-by: Xuan Ding <xuan.ding@intel.com>
> > Signed-off-by: Yuan Wang <yuanx.wang@intel.com>
> > ---
> >  lib/ethdev/rte_ethdev.c | 24 +++++++++++++----------
> > lib/ethdev/rte_ethdev.h | 43
> > +++++++++++++++++++++++++++++++++++++++--
> >  2 files changed, 55 insertions(+), 12 deletions(-)
> >
> > diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c index
> > 70c850a2f1..49c8fef1c3 100644
> > --- a/lib/ethdev/rte_ethdev.c
> > +++ b/lib/ethdev/rte_ethdev.c
> > @@ -1661,6 +1661,7 @@ rte_eth_rx_queue_check_split(const struct
> > rte_eth_rxseg_split *rx_seg,  struct rte_mempool *mpl =
> > rx_seg[seg_idx].mp;  uint32_t length = rx_seg[seg_idx].length;
> > uint32_t offset = rx_seg[seg_idx].offset;
> > +uint16_t proto = rx_seg[seg_idx].proto;
> >
> >  if (mpl == NULL) {
> >  RTE_ETHDEV_LOG(ERR, "null mempool pointer\n"); @@ -1692,15
> +1693,17
> > @@ rte_eth_rx_queue_check_split(const struct rte_eth_rxseg_split
> > *rx_seg,  (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;
> > +if (proto == 0) {
> > +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;
> > +}
> >  }
> 
> As the length and proto is exclusive, it better also check the length when
> proto!=0

Thanks for your comments, will fix it in next version.

> 
> .....
> 
> > @@ -1197,12 +1197,26 @@ struct rte_eth_txmode {
> >   *     - pool from the last valid element
> >   *     - the buffer size from this pool
> >   *     - zero offset
> > + *
> > + * Header split is a subset of buffer split. The split happens after
> > + the
> > + * packet header and before the packet payload. For PMDs that do not
> > + * support header split configuration by length and offset, the
> > + location
> > + * of the split needs to be specified by the header protocol type.
> > + While for
> > + * buffer split, this field should not be configured.
> > + *
> > + * If RTE_ETH_RX_OFFLOAD_HEADER_SPLIT flag is set in offloads field,
> > + * the PMD will split the received packets into two separate regions:
> > + * - The header buffer will be allocated from the memory pool,
> > + *   specified in the first array element, the second buffer, from the
> > + *   pool in the second element.
> > + * - The length and offset do not need to be configured in header split.
> 
> We may not necessarily ignore the offset configure for header split as there
> is no confliction, a driver still can support copying a split header to a specific
> mbuf offset And if we support offset with header split, offset boundary check
> can also be considered in rte_eth_rx_queue_check_split

You are right. Only length and proto is exclusive in between buffer split and header split.
Will update in next version.

Thanks,
Xuan

> 
> Regards
> Qi
> 
>