ba932ddabd
Cleanup document to convert old rxmode and txq_flags to new offload bit mask. Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
176 lines
6.0 KiB
ReStructuredText
176 lines
6.0 KiB
ReStructuredText
.. SPDX-License-Identifier: BSD-3-Clause
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Copyright(c) 2015-2016 Intel Corporation.
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FM10K Poll Mode Driver
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======================
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The FM10K poll mode driver library provides support for the Intel FM10000
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(FM10K) family of 40GbE/100GbE adapters.
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FTAG Based Forwarding of FM10K
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------------------------------
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FTAG Based Forwarding is a unique feature of FM10K. The FM10K family of NICs
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support the addition of a Fabric Tag (FTAG) to carry special information.
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The FTAG is placed at the beginning of the frame, it contains information
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such as where the packet comes from and goes, and the vlan tag. In FTAG based
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forwarding mode, the switch logic forwards packets according to glort (global
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resource tag) information, rather than the mac and vlan table. Currently this
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feature works only on PF.
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To enable this feature, the user should pass a devargs parameter to the eal
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like "-w 84:00.0,enable_ftag=1", and the application should make sure an
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appropriate FTAG is inserted for every frame on TX side.
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Vector PMD for FM10K
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--------------------
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Vector PMD (vPMD) uses Intel® SIMD instructions to optimize packet I/O.
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It improves load/store bandwidth efficiency of L1 data cache by using a wider
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SSE/AVX ''register (1)''.
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The wider register gives space to hold multiple packet buffers so as to save
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on the number of instructions when bulk processing packets.
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There is no change to the PMD API. The RX/TX handlers are the only two entries for
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vPMD packet I/O. They are transparently registered at runtime RX/TX execution
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if all required conditions are met.
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1. To date, only an SSE version of FM10K vPMD is available.
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To ensure that vPMD is in the binary code, set
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``CONFIG_RTE_LIBRTE_FM10K_INC_VECTOR=y`` in the configure file.
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Some constraints apply as pre-conditions for specific optimizations on bulk
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packet transfers. The following sections explain RX and TX constraints in the
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vPMD.
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RX Constraints
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~~~~~~~~~~~~~~
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Prerequisites and Pre-conditions
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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For Vector RX it is assumed that the number of descriptor rings will be a power
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of 2. With this pre-condition, the ring pointer can easily scroll back to the
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head after hitting the tail without a conditional check. In addition Vector RX
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can use this assumption to do a bit mask using ``ring_size - 1``.
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Features not Supported by Vector RX PMD
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Some features are not supported when trying to increase the throughput in
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vPMD. They are:
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* IEEE1588
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* Flow director
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* Header split
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* RX checksum offload
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Other features are supported using optional MACRO configuration. They include:
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* HW VLAN strip
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* L3/L4 packet type
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To enable via ``RX_OLFLAGS`` use ``RTE_LIBRTE_FM10K_RX_OLFLAGS_ENABLE=y``.
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To guarantee the constraint, the following capabilities in ``dev_conf.rxmode.offloads``
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will be checked:
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* ``DEV_RX_OFFLOAD_VLAN_EXTEND``
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* ``DEV_RX_OFFLOAD_CHECKSUM``
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* ``DEV_RX_OFFLOAD_HEADER_SPLIT``
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* ``fdir_conf->mode``
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RX Burst Size
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^^^^^^^^^^^^^
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As vPMD is focused on high throughput, it processes 4 packets at a time. So it assumes
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that the RX burst should be greater than 4 packets per burst. It returns zero if using
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``nb_pkt`` < 4 in the receive handler. If ``nb_pkt`` is not a multiple of 4, a
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floor alignment will be applied.
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TX Constraint
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~~~~~~~~~~~~~
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Features not Supported by TX Vector PMD
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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TX vPMD only works when offloads is set to 0
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This means that it does not support any TX offload.
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Limitations
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-----------
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Switch manager
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~~~~~~~~~~~~~~
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The Intel FM10000 family of NICs integrate a hardware switch and multiple host
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interfaces. The FM10000 PMD driver only manages host interfaces. For the
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switch component another switch driver has to be loaded prior to to the
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FM10000 PMD driver. The switch driver can be acquired from Intel support.
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Only Testpoint is validated with DPDK, the latest version that has been
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validated with DPDK is 4.1.6.
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Support for Switch Restart
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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For FM10000 multi host based design a DPDK app running in the VM or host needs
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to be aware of the switch's state since it may undergo a quit-restart. When
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the switch goes down the DPDK app will receive a LSC event indicating link
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status down, and the app should stop the worker threads that are polling on
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the Rx/Tx queues. When switch comes up, a LSC event indicating ``LINK_UP`` is
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sent to the app, which can then restart the FM10000 port to resume network
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processing.
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CRC striping
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~~~~~~~~~~~~
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The FM10000 family of NICs strip the CRC for every packets coming into the
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host interface. So, CRC will be stripped even when ``DEV_RX_OFFLOAD_CRC_STRIP``
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in ``rxmode.offloads`` is NOT set in ``struct rte_eth_conf``.
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Maximum packet length
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~~~~~~~~~~~~~~~~~~~~~
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The FM10000 family of NICS support a maximum of a 15K jumbo frame. The value
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is fixed and cannot be changed. So, even when the ``rxmode.max_rx_pkt_len``
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member of ``struct rte_eth_conf`` is set to a value lower than 15364, frames
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up to 15364 bytes can still reach the host interface.
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Statistic Polling Frequency
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~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The FM10000 NICs expose a set of statistics via the PCI BARs. These statistics
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are read from the hardware registers when ``rte_eth_stats_get()`` or
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``rte_eth_xstats_get()`` is called. The packet counting registers are 32 bits
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while the byte counting registers are 48 bits. As a result, the statistics must
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be polled regularly in order to ensure the consistency of the returned reads.
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Given the PCIe Gen3 x8, about 50Gbps of traffic can occur. With 64 byte packets
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this gives almost 100 million packets/second, causing 32 bit integer overflow
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after approx 40 seconds. To ensure these overflows are detected and accounted
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for in the statistics, it is necessary to read statistic regularly. It is
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suggested to read stats every 20 seconds, which will ensure the statistics
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are accurate.
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Interrupt mode
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~~~~~~~~~~~~~~
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The FM10000 family of NICS need one separate interrupt for mailbox. So only
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drivers which support multiple interrupt vectors e.g. vfio-pci can work
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for fm10k interrupt mode.
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