From: "Chen Jing D(Mark)" <jing.d.c...@intel.com> Add introductions on how to enable Vector FM10K Rx/Tx functions, the preconditions and assumptions on Rx/Tx configuration parameters. The new content also lists the limitations of vector, so app/customer can do better to select best Rx/Tx functions.
Signed-off-by: Chen Jing D(Mark) <jing.d.chen at intel.com> --- doc/guides/nics/fm10k.rst | 89 +++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 89 insertions(+), 0 deletions(-) diff --git a/doc/guides/nics/fm10k.rst b/doc/guides/nics/fm10k.rst index 4206b7f..54b761c 100644 --- a/doc/guides/nics/fm10k.rst +++ b/doc/guides/nics/fm10k.rst @@ -34,6 +34,95 @@ FM10K Poll Mode Driver The FM10K poll mode driver library provides support for the Intel FM10000 (FM10K) family of 40GbE/100GbE adapters. +Vector PMD for FM10K +-------------------- +Vector PMD uses Intel? SIMD instructions to optimize packet I/O. +It improves load/store bandwidth efficiency of L1 data cache by using a wider +SSE/AVX register 1 (1). +The wider register gives space to hold multiple packet buffers so as to save +instruction number when processing bulk of packets. + +There is no change to PMD API. The RX/TX handler are the only two entries for +vPMD packet I/O. They are transparently registered at runtime RX/TX execution +if all condition checks pass. + +1. To date, only an SSE version of FM10K vPMD is available. + To ensure that vPMD is in the binary code, ensure that the option + CONFIG_RTE_LIBRTE_FM10K_INC_VECTOR=y is in the configure file. + +Some constraints apply as pre-conditions for specific optimizations on bulk +packet transfers. The following sections explain RX and TX constraints in the +vPMD. + +RX Constraints +~~~~~~~~~~~~~~ + +Prerequisites and Pre-conditions +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +Number of descriptor ring must be power of 2. This is the assumptions for +Vector RX. With this pre-condition, ring pointer can easily scroll back to head +after hitting tail without conditional check. Besides that, Vector RX can use +it to do bit mask by ``ring_size - 1``. + +Feature not Supported by Vector RX PMD +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +Some features are not supported when trying to increase the throughput in vPMD. +They are: + +* IEEE1588 + +* FDIR + +* Header split + +* RX checksum offload + +Other features are supported using optional MACRO configuration. They include: + +* HW VLAN strip + +* L3/L4 packet type + +To enabled by RX_OLFLAGS (RTE_LIBRTE_FM10K_RX_OLFLAGS_ENABLE=y) + +To guarantee the constraint, configuration flags in dev_conf.rxmode will be +checked: + +* hw_vlan_extend + +* hw_ip_checksum + +* header_split + +* fdir_conf->mode + +RX Burst Size +^^^^^^^^^^^^^ + +As vPMD is focused on high throughput, which processes 4 packets at a time. +So it assumes that the RX burst should be greater than 4 per burst. It returns +zero if using nb_pkt < 4 in the receive handler. If nb_pkt is not multiple of +4, a floor alignment will be applied. + +TX Constraint +~~~~~~~~~~~~~ + +Feature not Supported by TX Vector PMD +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +TX vPMD only works when txq_flags is set to FM10K_SIMPLE_TX_FLAG. +This means that it does not support TX multi-segment, VLAN offload and TX csum +offload. The following MACROs are used for these three features: + +* ETH_TXQ_FLAGS_NOMULTSEGS + +* ETH_TXQ_FLAGS_NOVLANOFFL + +* ETH_TXQ_FLAGS_NOXSUMSCTP + +* ETH_TXQ_FLAGS_NOXSUMUDP + +* ETH_TXQ_FLAGS_NOXSUMTCP Limitations ----------- -- 1.7.7.6