[dpdk-dev] Redirection Table

Ivan Boule ivan.boule at 6wind.com
Tue Jan 7 09:35:59 CET 2014

On 01/06/2014 05:52 PM, Michael Quicquaro wrote:
> Thanks for the details.  Can the hash function be modified so that I 
> can provide my own RSS function?  i.e.  my ultimate goal is to provide 
> RSS that is not dependent on packet contents.
No, the RSS function is "hard-wired" and only works on IPv4/IPv6 
packets. All other packets are stored in the same queue (0 by default).
You can change the RSS key used by the RSS function to compute the hash 
See the following testpmd command:

    port config X rss-hash-key <80 hexa digits>

to set the 320-bit RSS key of port X.

Best regards,

> You may have seen my thread "generic load balancing".  At this point, 
> I'm realizing that the only way to accomplish this is to let the 
> packets land where they may (the queue where the NIC places the 
> packet) and distribute them (to other queues) by having some of the 
> CPU processing devoted to this task.  Can you verify this?
> Regards,
> - Michael.
> On Mon, Jan 6, 2014 at 10:21 AM, Ivan Boule <ivan.boule at 6wind.com 
> <mailto:ivan.boule at 6wind.com>> wrote:
>     On 12/31/2013 08:45 PM, Michael Quicquaro wrote:
>         Has anyone used the "port config all reta (hash,queue)"
>         command of testpmd
>         with any success?
>         I haven't found much documentation on it.
>         Can someone provide an example on why and how it was used.
>         Regards and Happy New Year,
>         Michael Quicquaro
>     Hi Michael,
>     "RETA" stands for Redirection Table.
>     It is a per-port configurable table of 128 entries that is used by the
>     RSS filtering feature of Intel 1GbE and 10GbE controllers to
>     select the
>     RX queue into which to store a received IP packet.
>     When receiving an IPv4/IPv6 packet, the controller computes a 32-bit
>     hash on:
>       * the source address and the destination address of the IP header of
>         the packet,
>       * the source port and the destination port of the UDP/TCP
>     header, if any.
>     Then, the controller takes the 7 lower bits of the RSS hash as an
>     index
>     into the RETA table to get the RX queue number where to store the
>     packet.
>     The API of the DPDK includes a function that is exported by Poll Mode
>     Drivers to configure RETA entries of a given port.
>     For test purposes, the testpmd application includes the following
>     command
>         "port config X rss reta (hash,queue)[,(hash,queue)]"
>     to configure RETA entries of a port X, with each couple (hash,queue)
>     contains the index of a RETA entry (between 0 and 127 included)
>     and the
>     RX queue number (between 0 and 15) to be stored into that RETA entry.
>     Best regards
>     Ivan
>     -- 
>     Ivan Boule
>     6WIND Development Engineer

Ivan Boule
6WIND Development Engineer

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