On Fri, 4 Mar 2005 20:52:39 +0100
Edgar E Iglesias <edgar.iglesias@xxxxxxxx> wrote:
> On Thu, Mar 03, 2005 at 05:26:51PM -0500, jamal wrote:
> > On Thu, 2005-03-03 at 17:02, John Heffner wrote:
> > > On Thu, 3 Mar 2005, Stephen Hemminger wrote:
> > > > Maybe a simple Random Exponential Drop (RED) would be more friendly.
> > >
> > > That would probably not be appropriate. This queue is only for absorbing
> > > micro-scale bursts. It should not hold any data in steady state like a
> > > router queue can. The receive window can handle the macro scale flow
> > > control.
> >
> > recall this is a queue that is potentially shared by many many flows
> > from potentially many many interfaces i.e it deals with many many
> > micro-scale bursts.
> > Clearly, the best approach is to have lots and lots of memmory and to
> > make that queue real huge so it can cope with all of them all the time.
> > We dont have that luxury - If you restrict the queue size, you will have
> > to drop packets... Which ones?
> > Probably simplest solution is to leave it as is right now and just
> > adjust the contraints based on your system memmory etc.
> >
>
> Why not have smaller queues but per interface? this would avoid
> introducing too much latency and keep memory consumption low
> but scale as we add more interfaces. It would also provide some
> kind of fair queueing between the interfaces to avoid highspeed
> nics to starve lowspeed ones.
That would require locking and effectively turn every device
into a NAPI device.
> Queue length would still be an issue though, should somehow be
> related to interface rate and acceptable introduced latency.
>
> Regarding RED and other more sophisticated algorithms, I assume
> this is up to the ingress qdisc to take care of. What the queues
> before the ingress qdiscs should do, is to avoid introducing
> too much latency. In my opinion, low latency or high burst
> tolerance should be the choice of the admin, like for egress.
>
All this happens at a much lower level before the ingress qdisc
(which is optional) gets involved.
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