netdev - Re: [PATCH V3 2/2] bonding support for IPv6 transmit hashing

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Message-ID: <4FEF55A7.6070502@8192.net>
Date:	Sat, 30 Jun 2012 12:38:15 -0700
From:	John <linux@...2.net>
To:	Hannes Frederic Sowa <hannes@...lcolloid.de>
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH V3 2/2] bonding support for IPv6 transmit hashing

On 6/30/2012 4:59 AM, Hannes Frederic Sowa wrote:
> On Sat, Jun 30, 2012 at 8:17 AM, John <linux@...2.net> wrote:
>> diff --git a/Documentation/networking/bonding.txt
>> b/Documentation/networking/bonding.txt
>> index bfea8a3..5db14fe 100644
>> --- a/Documentation/networking/bonding.txt
>> +++ b/Documentation/networking/bonding.txt
>> @@ -752,12 +752,22 @@ xmit_hash_policy
>>                  protocol information to generate the hash.
>>
>>                  Uses XOR of hardware MAC addresses and IP addresses to
>> -               generate the hash.  The formula is
>> +               generate the hash.  The IPv4 formula is
>>
>>                  (((source IP XOR dest IP) AND 0xffff) XOR
>>                          ( source MAC XOR destination MAC ))
>>                                  modulo slave count
>>
>> +               The IPv6 forumla is
>> +
>> +               iphash =
>> +                       (source ip quad 2 XOR dest IP quad 2) XOR
>> +                       (source ip quad 3 XOR dest IP quad 3) XOR
>> +                       (source ip quad 4 XOR dest IP quad 4)
>> +
>> +               ((iphash >> 16) XOR (iphash >> 8) XOR iphash)
>> +                       modulo slave count
>> +
>
> Wouldn't it be beneficial to include the ipv6 flow label in the hash
> calculation?
>
> Greetings,
>
>    Hannes
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Hannes,

In all of the traffic I inspected I don't believe I saw a single flow 
label set. Even if it were set 100% of the time by Linux, any packets 
routed or bridged from another operating system wouldn't see any 
benefit. The current algorithm distributes the traffic very well, I 
don't believe adding the flow label would be beneficial even if it were 
set more frequently.

If you feel strongly about its inclusion, though, I am willing to 
reconsider.

John

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