netdev - Re: [PATCH v2 net-next] net/sched: add skbprio scheduler

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Date:   Sun, 24 Jun 2018 11:43:07 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Nishanth Devarajan <ndev2021@...il.com>, xiyou.wangcong@...il.com,
        jiri@...nulli.us, davem@...emloft.net
Cc:     netdev@...r.kernel.org, doucette@...edu, michel@...irati.com.br,
        alexander.duyck@...il.com
Subject: Re: [PATCH v2 net-next] net/sched: add skbprio scheduler

On 23/06/18 04:47 PM, Nishanth Devarajan wrote:
[..]

> +	/* Drop the packet at the tail of the lowest priority qdisc. */
> +	lp_qdisc = &q->qdiscs[lp];
> +	to_drop = __skb_dequeue_tail(lp_qdisc);
> +	BUG_ON(!to_drop);
> +	qdisc_qstats_backlog_dec(sch, to_drop);
> +	qdisc_drop(to_drop, sch, to_free);
> +

Maybe also increase overlimit stat here? It will keep track
of low prio things dropped because you were congested.
Such a stat helps when debugging or collecting analytics.

Per Alex's comment, how about:

-----------
Skbprio (SKB Priority Queue) is a queueing discipline that
prioritizes packets according to their skb->priority field.
Under congestion, already-enqueued lower priority packets
will be dropped to make space available for higher priority
packets. Skbprio was conceived as a solution for
denial-of-service defenses that need to route packets with
different priorities as a means to overcome DoS attacks
as described in paper xxxx...


cheers,
jamal