netdev - Re: HTB going crazy over ~5Gbit/s (4.12.9, but problem present in older kernels as well)

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Message-ID: <1505325803.15310.184.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Wed, 13 Sep 2017 11:03:23 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Denys Fedoryshchenko <nuclearcat@...learcat.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        netdev-owner@...r.kernel.org
Subject: Re: HTB going crazy over ~5Gbit/s (4.12.9, but problem present in
 older kernels as well)

On Wed, 2017-09-13 at 10:58 -0700, Eric Dumazet wrote:
> On Wed, 2017-09-13 at 20:35 +0300, Denys Fedoryshchenko wrote:
> 
> > Overlimits never appear in HTB as i know, here is simulation on this 
> > class that have constant "at least" 1G traffic, i throttled it to 1Kbit 
> > to simulate forced drops:
> > 
> > shapernew ~ # sh /etc/shaper.cfg;sleep 1;tc -s -d class show dev 
> > eth3.777 classid 1:111;tc qdisc del dev eth3.777 root
> > class htb 1:111 parent 1:1 leaf 111: prio 0 quantum 50000 rate 1Kbit 
> > ceil 1Kbit linklayer ethernet burst 31280b/1 mpu 0b cburst 31280b/1 mpu 
> > 0b level 0
> >   Sent 134350019 bytes 117520 pkt (dropped 7819, overlimits 0 requeues 0)
> >   backlog 7902126b 4976p requeues 0
> >   lended: 86694 borrowed: 0 giants: 0
> >   tokens: -937500000 ctokens: -937500000
> > 
> 
> Oh right, I am using a local patch for this. Time to upstream :/

Please try :

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 7e148376ba528efabe5a53a09653f9161c264be7..c6d7ae81b41f4e277afb93a3003fefcd3f27de35 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -142,6 +142,7 @@ struct htb_class {
        struct rb_node          node[TC_HTB_NUMPRIO];   /* node for self or feed tree */
 
        unsigned int drops ____cacheline_aligned_in_smp;
+       unsigned int            overlimits;
 };
 
 struct htb_level {
@@ -533,6 +534,9 @@ 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)
+               cl->overlimits++;
+
        if (cl->prio_activity) {        /* not necessary: speed optimization */
                if (cl->cmode != HTB_CANT_SEND)
                        htb_deactivate_prios(q, cl);
@@ -1143,6 +1147,7 @@ htb_dump_class_stats(struct Qdisc *sch, unsigned long arg, struct gnet_dump *d)
        struct htb_class *cl = (struct htb_class *)arg;
        struct gnet_stats_queue qs = {
                .drops = cl->drops,
+               .overlimits = cl->overlimits,
        };
        __u32 qlen = 0;