Hello list!
(CC'in Jack Vogel since this is intel drivers/hardware specific question)
There are some techniques for assigning network traffic to different NIC
RX queues (bound to different CPUs/cores).
The main problem for all techniques is avoiding any possible packet
reordering in single flow.
Most obvious (and most used) are described in Microsoft NDIS driver
specification:
Hashing is done on various tuples like:
* IPv46 src/dst + TCP/UDP src/dst port for TCP/UDP
* IPv46 src/dst for general IPv46 traffic
igb's have a bit more options like assigning selected ethertype or TCP
SYN to different queue (See section 7.1.1 of 82576EB datasheet)
ixgbe (82599) goes even more far: flow director functionality permits 8K
'perfect match' filters allowing to select any subset in:
* vlan
* IPv46 src/dst
* L4 proto
* TCP/UDP/SCTP protocol ports
and even 'flexible 2-byte tuple anywhere in the first 64 bytes of the
packet'
There are other possibilities to assign traffic to different queues in
ixbge like using .1q priority filed (DCB functionality)
More information can be found in sections 7.1.2 (RX queues assignment),
7.1.2.7(Flow Director), 7.7.1 (DCB) of 82599 datasheet
However, there are many setups where PC can be used as platform for
routing/dispatching non-IP traffic.
PPPoE server is a typical example.
People have to do some tricks (link aggregation, non-direct ISR) to get
traffic dispatched by more than single CPU/core, but this much less
efficient.
I'm a bit curious: why some generic hashing mechanism based on something
like 'flexible 2-byte tuple anywhere in the first 64 bytes of the
packet' were not added?
It can be (at least from my point of view) easily based on (for example)
flow director functionality.
Particularly I'm trying to figure out how can I use all this variety of
filters to get MPLS traffic split to different RX queues.
Maybe someone can point me to the right direction?
--
Alexander V. Chernikov
Yandex NOC
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