|author||Yongseok Koh <email@example.com>||2018-05-09 04:13:50 -0700|
|committer||Ferruh Yigit <firstname.lastname@example.org>||2018-05-14 22:31:52 +0100|
net/mlx5: add Multi-Packet Rx support
Multi-Packet Rx Queue (MPRQ a.k.a Striding RQ) can further save PCIe bandwidth by posting a single large buffer for multiple packets. Instead of posting a buffer per a packet, one large buffer is posted in order to receive multiple packets on the buffer. A MPRQ buffer consists of multiple fixed-size strides and each stride receives one packet. Rx packet is mem-copied to a user-provided mbuf if the size of Rx packet is comparatively small, or PMD attaches the Rx packet to the mbuf by external buffer attachment - rte_pktmbuf_attach_extbuf(). A mempool for external buffers will be allocated and managed by PMD. Signed-off-by: Yongseok Koh <email@example.com> Acked-by: Shahaf Shuler <firstname.lastname@example.org>
Diffstat (limited to 'doc/guides/nics/mlx5.rst')
1 files changed, 58 insertions, 0 deletions
diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index 13cc3f8..a7d5c90 100644
@@ -105,10 +105,14 @@ Limitations
- A multi segment packet must have less than 6 segments in case the Tx burst function
is set to multi-packet send or Enhanced multi-packet send. Otherwise it must have
less than 50 segments.
- Count action for RTE flow is **only supported in Mellanox OFED**.
- Flows with a VXLAN Network Identifier equal (or ends to be equal)
to 0 are not supported.
- VXLAN TSO and checksum offloads are not supported on VM.
- VF: flow rules created on VF devices can only match traffic targeted at the
configured MAC addresses (see ``rte_eth_dev_mac_addr_add()``).
@@ -119,6 +123,13 @@ Limitations
the device. In case of ungraceful program termination, some entries may
remain present and should be removed manually by other means.
+- When Multi-Packet Rx queue is configured (``mprq_en``), a Rx packet can be
+ externally attached to a user-provided mbuf with having EXT_ATTACHED_MBUF in
+ ol_flags. As the mempool for the external buffer is managed by PMD, all the
+ Rx mbufs must be freed before the device is closed. Otherwise, the mempool of
+ the external buffers will be freed by PMD and the application which still
+ holds the external buffers may be corrupted.
@@ -229,6 +240,53 @@ Run-time configuration
- x86_64 with ConnectX-4, ConnectX-4 LX and ConnectX-5.
- POWER8 and ARMv8 with ConnectX-4 LX and ConnectX-5.
+- ``mprq_en`` parameter [int]
+ A nonzero value enables configuring Multi-Packet Rx queues. Rx queue is
+ configured as Multi-Packet RQ if the total number of Rx queues is
+ ``rxqs_min_mprq`` or more and Rx scatter isn't configured. Disabled by
+ Multi-Packet Rx Queue (MPRQ a.k.a Striding RQ) can further save PCIe bandwidth
+ by posting a single large buffer for multiple packets. Instead of posting a
+ buffers per a packet, one large buffer is posted in order to receive multiple
+ packets on the buffer. A MPRQ buffer consists of multiple fixed-size strides
+ and each stride receives one packet. MPRQ can improve throughput for
+ small-packet tarffic.
+ When MPRQ is enabled, max_rx_pkt_len can be larger than the size of
+ user-provided mbuf even if DEV_RX_OFFLOAD_SCATTER isn't enabled. PMD will
+ configure large stride size enough to accommodate max_rx_pkt_len as long as
+ device allows. Note that this can waste system memory compared to enabling Rx
+ scatter and multi-segment packet.
+- ``mprq_log_stride_num`` parameter [int]
+ Log 2 of the number of strides for Multi-Packet Rx queue. Configuring more
+ strides can reduce PCIe tarffic further. If configured value is not in the
+ range of device capability, the default value will be set with a warning
+ message. The default value is 4 which is 16 strides per a buffer, valid only
+ if ``mprq_en`` is set.
+ The size of Rx queue should be bigger than the number of strides.
+- ``mprq_max_memcpy_len`` parameter [int]
+ The maximum length of packet to memcpy in case of Multi-Packet Rx queue. Rx
+ packet is mem-copied to a user-provided mbuf if the size of Rx packet is less
+ than or equal to this parameter. Otherwise, PMD will attach the Rx packet to
+ the mbuf by external buffer attachment - ``rte_pktmbuf_attach_extbuf()``.
+ A mempool for external buffers will be allocated and managed by PMD. If Rx
+ packet is externally attached, ol_flags field of the mbuf will have
+ EXT_ATTACHED_MBUF and this flag must be preserved. ``RTE_MBUF_HAS_EXTBUF()``
+ checks the flag. The default value is 128, valid only if ``mprq_en`` is set.
+- ``rxqs_min_mprq`` parameter [int]
+ Configure Rx queues as Multi-Packet RQ if the total number of Rx queues is
+ greater or equal to this value. The default value is 12, valid only if
+ ``mprq_en`` is set.
- ``txq_inline`` parameter [int]
Amount of data to be inlined during TX operations. Improves latency.