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Subject: Re: UDP/TCP versus IP frames - subtle out of order packets with
 hardware hashing
From: Adrian Chadd <adrian@freebsd.org>
To: Slawa Olhovchenkov <slw@zxy.spb.ru>
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On 15 July 2014 04:33, Slawa Olhovchenkov <slw@zxy.spb.ru> wrote:
> On Tue, Jul 15, 2014 at 03:22:34PM +0430, Hooman Fazaeli wrote:
>
>> On 7/15/2014 2:01 PM, Slawa Olhovchenkov wrote:
>> > On Tue, Jul 15, 2014 at 01:31:52PM +0430, Hooman Fazaeli wrote:
>> >
>> >> Doesn't the problem applies to TCP too?
>> >> TCP may be fragmented too but is less likely because of MSS.
>> > Don't forget GRE, IPIP, ESP and AH!
>> >
>> These protocols don't use port numbers  and the RSS hash is computed based on the
>> (srcip,dstip) tuple, so the problem does not apply to them.
>
> And all flows go to one queue? Bad.

All the packets between two IP addresses for non-TCP, non-UDP get
hashed to the same CPU core, yes.

If you have 1000 IP tunnels to different end-hosts, they'll be on
different CPUs.


-a