From: Avi Kivity <avi@cloudius-systems.com>
To: "Matthew Hall" <mhall@mhcomputing.net>,
"Martin Drašar" <drasar@ics.muni.cz>
Cc: dev@dpdk.org
Subject: Re: Broken RSS hash computation on Intel 82574L
Date: Tue, 1 Sep 2015 17:50:16 +0300 [thread overview]
Message-ID: <55E5BB28.1090009@cloudius-systems.com> (raw)
In-Reply-To: <20150901144726.GA30421@mhcomputing.net>
On 09/01/2015 05:47 PM, Matthew Hall wrote:
> On Tue, Sep 01, 2015 at 04:37:18PM +0200, Martin Drašar 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 hashes.
>>>
>>> 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 hashes
>> would help me a lot. The computer which is using those NICs is not that
>> 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 it.
>
As an example, seastar uses the RSS hash computed by the NIC to select a
core to process on, if the number of hardware queues is smaller than the
number of cores.
next prev parent reply other threads:[~2015-09-01 14:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-31 12:15 Broken RSS hash computation on Intel 82574L Martin Drašar
2015-09-01 13:45 ` De Lara Guarch, Pablo
2015-09-01 14:37 ` Martin Drašar
2015-09-01 14:47 ` Matthew Hall
2015-09-01 14:50 ` Avi Kivity [this message]
2015-09-01 15:00 ` Martin Drašar
2015-09-01 15:19 ` Jim Thompson
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