Commit b362487a authored May 04, 2019 by Cong Wang Committed by David S. Miller May 05, 2019

sch_htb: redefine htb qdisc overlimits



In commit 3c75f6ee ("net_sched: sch_htb: add per class overlimits counter")
we added an overlimits counter for each HTB class which could
properly reflect how many times we use up all the bandwidth
on each class. However, the overlimits counter in HTB qdisc
does not, it is way bigger than the sum of each HTB class.
In fact, this qdisc overlimits counter increases when we have
no skb to dequeue, which happens more often than we run out of
bandwidth.

It makes more sense to make this qdisc overlimits counter just
be a sum of each HTB class, in case people still get confused.

I have verified this patch with one single HTB class, where HTB
qdisc counters now always match HTB class counters as expected.

Eric suggested we could fold this field into 'direct_pkts' as
we only use its 32bit on 64bit CPU, this saves one cache line.

Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent f452825d

net/sched/sch_htb.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -165,7 +165,8 @@ struct htb_sched {

		/* non shaped skbs; let them go directly thru */
		struct qdisc_skb_head direct_queue;
		long direct_pkts;
		u32 direct_pkts;
		u32 overlimits;

		struct qdisc_watchdog watchdog;

		@@ -533,8 +534,10 @@ htb_change_class_mode(struct htb_sched q, struct htb_class cl, s64 *diff)
		if (new_mode == cl->cmode)
		return;

		if (new_mode == HTB_CANT_SEND)
		if (new_mode == HTB_CANT_SEND) {
		cl->overlimits++;
		q->overlimits++;
		}

		if (cl->prio_activity) { /* not necessary: speed optimization */
		if (cl->cmode != HTB_CANT_SEND)
		@@ -937,7 +940,6 @@ ok:
		goto ok;
		}
		}
		qdisc_qstats_overlimit(sch);
		if (likely(next_event > q->now))
		qdisc_watchdog_schedule_ns(&q->watchdog, next_event);
		else
		@@ -1048,6 +1050,7 @@ static int htb_dump(struct Qdisc sch, struct sk_buff skb)
		struct nlattr *nest;
		struct tc_htb_glob gopt;

		sch->qstats.overlimits = q->overlimits;
		/* Its safe to not acquire qdisc lock. As we hold RTNL,
		* no change can happen on the qdisc parameters.
		*/

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