[ovs-dev] [PATCH v2] Simplify kernel sFlow implementation

[Jesse Gross]

On Aug 18, 2011 2:51 AM, "Pravin Shelar" <pshelar at nicira.com> wrote:
>
> On Tue, Aug 16, 2011 at 11:17 PM, Jesse Gross <jesse at nicira.com> wrote:
> > On Mon, Aug 15, 2011 at 8:34 PM, pravin shelar <pshelar at nicira.com>
wrote:
> >>   This patch makes sampling support more generic/simple by adding
> >>  Datapath SAMPLING action. When sampling is turned on, a SAMPLING
> >>  action is added to all flows for given bridge.
> >>   This patch cleanup sampling upcall by striping it down to minimum
> >>  essential that userspace can not figure out for itself. Now sample
> >>  packet is sent along with actions checksum. So that sflow module can
> >>  make sure it has consistent actions.
> >
> > I'm not sure that this does much to simplify or genericize sampling.
> > For the sample action itself, I was expecting something that could be
> > used to execute any set of actions with a given probability but this
> > is still tied towards sending packets to userspace with a fixed
> > probability across the datapath.  This would truly be generic and the
> > word "sFlow" would not appear in the kernel at all but could be
> > implemented entirely in userspace based on these primitives.  Does
> > this make sense to you?
>
> I think patch is first step toward that.
>
> My idea is to have sampling action with arguments like probability(P)
> and action(A). When probability(P) is hit, passed action (A) could be
> executed on that packet. But i dont like to generalize when there is
> only one use case at present where we need to assign probability. it
> just keeps things simple.

I mentioned this on the phone but just for everybody else's benefit:

My main goal here is to come up with an interface that is as close to final
as we can get it. While in general I agree with incremental work, in this
case I think we need to go the full way in regards to the interface.
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