From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@cloudius-systems.com>
Subject: Re: Broken RSS hash computation on Intel 82574L
Date: Tue, 1 Sep 2015 17:50:16 +0300
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 <E115CCD9D858EF4F90C690B0DCB4D8973C7EF8C0@IRSMSX108.ger.corp.intel.com>
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To: Matthew Hall <mhall@mhcomputing.net>, =?UTF-8?Q?Martin_Dra=c5=a1ar?=
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On 09/01/2015 05:47 PM, Matthew Hall wrote:
> On Tue, Sep 01, 2015 at 04:37:18PM +0200, Martin Dra=C5=A1ar wrote:
>> Dne 1.9.2015 v 15:45 De Lara Guarch, Pablo napsal(a):
>>> 82574L NIC uses em PMD, which does not support more than 1 queue.
>>> Therefore RSS is disabled in the NIC and then you cannot have RSS has=
hes.
>>>
>>> Thanks,
>>> Pablo
>> Hi Pablo,
>>
>> that is an interesting information. I read the rationale in em_ethdev.=
c
>> and I was wondering, what would have to be done to enable RSS hash
>> computation on that card. I can live with just one RX queue, but hashe=
s
>> would help me a lot. The computer which is using those NICs is not tha=
t
>> powerful and every bit of offloaded computation counts...
>>
>> Thanks,
>> Martin
> RSS calculations are used to direct packets across multiple RX queues. =
With
> only one RX queue it cannot possibly increase performance by enabling i=
t.
>

As an example, seastar uses the RSS hash computed by the NIC to select a=20
core to process on, if the number of hardware queues is smaller than the=20
number of cores.