Re: rps perfomance WAS(Re: rps: question

Eric Dumazet
2010-04-14T19:58:58Z

Le mercredi 14 avril 2010 à 12:44 -0700, Stephen Hemminger a écrit :
> On Wed, 14 Apr 2010 14:53:42 -0400
> jamal <hadi@cyberus.ca> wrote:
>
> > Agreed. So to enumerate, the benefits come in if:
> > a) you have many processors
> > b) you have single-queue nic
> > c) at sub-threshold traffic you dont care about a little latency
>
> There probably needs to be better autotuning for this, there is no reason
> that RPS to be steering packets unless the queue is getting backed up.
> Some kind of high / low water mark mechanism is needed.
>
> RPS might also interact with the core turbo boost functionality on Intel chips.
> Newer chips will make a single core faster if other core can be kept idle.
>
>

This was discussed a while ago, and Out Of Order packet delivery was the
thing that frightened us a bit.

Every time we change RPS to be on or off, we might have some extra
noise. Maybe we already have this problem with irqbalance ?