netdev - Re: [PATCH v3 net-next] net/sched: add skbprio scheduler

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Message-ID: <20180714045101.GB20383@localhost.localdomain>
Date:   Sat, 14 Jul 2018 01:51:02 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Michel Machado <michel@...irati.com.br>,
        Nishanth Devarajan <ndev2021@...il.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        David Miller <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Cody Doucette <doucette@...edu>
Subject: Re: [PATCH v3 net-next] net/sched: add skbprio scheduler

On Fri, Jul 13, 2018 at 11:17:18AM -0700, Cong Wang wrote:
...
> > > > > Isn't the whole point of sch_prio offloading the queueing to
> > > > > each class? If you need a limit, there is one for each child
> > > > > qdisc if you use for example pfifo or bfifo (depending on you
> > > > > want to limit bytes or packets).
> > > >
> > > > Yes, but Michel wants to drop from other lower priorities if needed,
> > > > and that's not possible if you handle the limit already in a child
> > > > qdisc as they don't know about their siblings. The idea in the example
> > > > above is to discard it from whatever lower priority is needed, then
> > > > queue it. (ok, the example missed to check the priority level)
> > >
> > > So it disproves your point of adding a flag to sch_prio, right?
> >
> > I don't see how?
> 
> Interesting, you said "Michel wants to drop from other lower
> priorities if needed", but sch_prio has no knowledge of this,
> you confirmed with "...if you handle the limit already in a child
> qdisc as they don't know about their siblings."
> 
> The if clause is true as the limit is indeed handled by its child
> qdiscs as designed.
> 
> Therefore, a simple of adding a flag to sch_prio, as you
> suggested and demonstrated above, doesn't work, as
> confirmed by your own words.

Well, it would help if you didn't cut out key parts of my words.

> 
> What am I missing here?
> 
> Are you go further by suggesting moving the limit out of prio?
> Or are you going to expand your definition of "adding a flag"?
> Perhaps two flags? :)
> 
> I am very open for discussion to see how far we can go.

I am not keen on continuing this discussion if you keep twisting my
words just for fun.