On Mon, Apr 19, 2010 at 10:59 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
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> Le mardi 20 avril 2010 à 07:38 +0800, Changli Gao a écrit :
>
>> Does this problem has relationship with your patch? No. If the rxhash
>> isn't provided by hardware, we can get more throughput from you patch,
>> and on the other side, we don't lose anything but potential more hash
>> collision.
>>
>
> I am not sure what you call hash collision. There is no hash chain here.
>
> This 32bit hash is a jhash one, and we only need 1 to 12 bits in it, I
> am pretty sure its OK.
>
Maybe for the purposes of RPS, but hash collisions could definitely be
an issue in RFS.  If two active connections hit the same rps_flow
entry this may cause thrashing of those connections between CPUs.  I
think your patch may increase the probability of this happening.

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