Cake - FQ_codel the next generation
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From: Georgios Amanakis <gamanakis@gmail.com>
To: "Toke Høiland-Jørgensen" <toke@toke.dk>
Cc: Jonathan Morton <chromatix99@gmail.com>,
	Cake List <cake@lists.bufferbloat.net>
Subject: Re: [Cake] cake at 60gbit
Date: Thu, 5 Jul 2018 19:48:07 -0400	[thread overview]
Message-ID: <CACvFP_hR3WZ4m++HZB_Mixo3Fw4hOxRjmxCqa6E+K85ixd3WiQ@mail.gmail.com> (raw)
In-Reply-To: <8736wxco28.fsf@toke.dk>

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I am going to give it a try, with your patch applied tonight and report.
Thank you!

George

On Thu, Jul 5, 2018, 6:31 PM Toke Høiland-Jørgensen <toke@toke.dk> wrote:

> Toke Høiland-Jørgensen <toke@toke.dk> writes:
>
> > Jonathan Morton <chromatix99@gmail.com> writes:
> >
> >>> On 3 Jul, 2018, at 1:23 am, Toke Høiland-Jørgensen <toke@toke.dk>
> wrote:
> >>>
> >>> My hunch is that this has something to do with the way mlx5 uses
> >>> multiple receive queues (and thus multiple CPUs). Which is probably
> >>> different from veth...
> >>
> >> At this stage I'm pretty confident it has nothing to do with Cake, and
> >> everything to do with the Mellanox hardware and driver. It does strike
> >> me that Linux' default handling of multiqueue hardware doesn't map
> >> very well to the qdisc interface.
> >
> > Well, it doesn't happen with fq_codel, so even if it is a driver bug, it
> > is being triggered by cake specifically...
>
> Right, so finally got some time to investigate this further.
>
> I suspected that cake_dequeue() was looping forever, so I added some
> debug statements to investigate this; and turns out I was right. Using
> the debug patch below, in unlimited mode I get loop aborts on loop 'i'
> for unlimited mode and loop 'l' if I enable the shaper at 70 gbit. It
> happens pretty reliably, but only when I load up the link sufficiently
> (need 4-6 TCP flows which get ~50 Gbps of total throughput).
>
> The weird thing is that what appears to be happening, is that cake
> somehow gets into a state where sch->q.qlen is >0 while all tin backlogs
> are 0. I have no clue how this happens; as far as I can tell, all
> changes to tin_backlog are paired with a change to q.qlen. The only
> thing outside of cake itself that modifies q.qlen is peek(), which is
> not being used here.
>
> I'm giving up for tonight; if anyone else has any ideas, I'm all ears.
>
> -Toke
>
> Sample debug output:
>
> [ 5456.068281] Loop counter i hit 100k; aborting! i 100001 j 0 k 180 l 3 m
> 0 qlen 2 qbkllog 33184 tin 2 deficit 172 tot backlog 0
>
> With this debug patch:
>
> @@ -1892,6 +1892,20 @@ static struct sk_buff *cake_dequeue(struct Qdisc
> *sch)
>         u64 delay;
>         u32 len;
>
> +       int i=0,j=0,k=0,l=0,m=0;
> +
> +#define COUNT_LOOP(v) do {                     \
> +               if (++v > 100000) {             \
> +                       int tot_bkl = 0;                                \
> +                       struct cake_tin_data *t;                        \
> +                       int n;                                          \
> +                       for(n=0,t = q->tins; n < CAKE_MAX_TINS; n++,t++)
>       \
> +                               tot_bkl += t->tin_backlog;              \
> +                       net_warn_ratelimited("Loop counter " #v " hit
> 100k; aborting! i %d j %d k %d l %d m %d qlen %d qbkllog %d tin %d deficit
> %d tot backlog %d", i, j, k, l, m, sch->q.qlen, sch->qstats.backlog,
> q->cur_tin, b->tin_deficit, tot_bkl); \
> +                       return NULL;                                    \
> +               }                                                       \
> +       } while(0);
> +
>  begin:
>         if (!sch->q.qlen)
>                 return NULL;
> @@ -1912,6 +1926,7 @@ begin:
>                 /* In unlimited mode, can't rely on shaper timings, just
> balance
>                  * with DRR
>                  */
> +               i=0;
>                 while (b->tin_deficit < 0 ||
>                        !(b->sparse_flow_count + b->bulk_flow_count)) {
>                         if (b->tin_deficit <= 0)
> @@ -1923,6 +1938,7 @@ begin:
>                                 q->cur_tin = 0;
>                                 b = q->tins;
>                         }
> +                       COUNT_LOOP(i);
>                 }
>         } else {
>                 /* In shaped mode, choose:
> @@ -1960,8 +1976,10 @@ retry:
>                         head = &b->old_flows;
>                         if (unlikely(list_empty(head))) {
>                                 head = &b->decaying_flows;
> -                               if (unlikely(list_empty(head)))
> +                               if (unlikely(list_empty(head))) {
> +                                       COUNT_LOOP(j);
>                                         goto begin;
> +                               }
>                         }
>                 }
>         }
> @@ -2008,6 +2026,7 @@ retry:
>                                 flow->set = CAKE_SET_SPARSE_WAIT;
>                         }
>                 }
> +               COUNT_LOOP(k);
>                 goto retry;
>         }
>
> @@ -2050,6 +2069,7 @@ retry:
>                                 srchost->srchost_refcnt--;
>                                 dsthost->dsthost_refcnt--;
>                         }
> +                       COUNT_LOOP(l);
>                         goto begin;
>                 }
>
> @@ -2075,6 +2095,8 @@ retry:
>                 kfree_skb(skb);
>                 if (q->rate_flags & CAKE_FLAG_INGRESS)
>                         goto retry;
> +
> +               COUNT_LOOP(m);
>         }
>
>         b->tin_ecn_mark += !!flow->cvars.ecn_marked;
>
>
>
>

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  reply	other threads:[~2018-07-05 23:48 UTC|newest]

Thread overview: 77+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <mailman.381.1530347349.3512.cake@lists.bufferbloat.net>
2018-06-30 16:37 ` [Cake] Cake on openwrt - falling behind Georgios Amanakis
2018-06-30 17:26   ` Pete Heist
2018-06-30 18:09     ` Georgios Amanakis
2018-06-30 18:55       ` Kevin Darbyshire-Bryant
2018-06-30 19:57         ` Pete Heist
2018-06-30 20:58           ` Georgios Amanakis
2018-06-30 21:37             ` Pete Heist
2018-06-30 22:43               ` Pete Heist
2018-06-30 23:20                 ` Pete Heist
     [not found]                   ` <CACvFP_gkdAPKSEO7j9+cMPqTa-fJYd8XFEEBD6ZzLuVvaNwsvg@mail.gmail.com>
2018-07-01  2:37                     ` [Cake] Fwd: " Georgios Amanakis
2018-07-01  7:18                       ` [Cake] " Pete Heist
2018-07-01 13:48                         ` Pete Heist
2018-07-01 14:02                           ` Dave Taht
2018-07-01 15:30                             ` Pete Heist
2018-07-01 14:38                           ` Kevin Darbyshire-Bryant
2018-07-01 16:54                             ` Pete Heist
2018-07-01 19:41                               ` Kevin Darbyshire-Bryant
2018-07-02 10:19                                 ` Pete Heist
2018-07-02 11:38                                   ` Pete Heist
2018-07-02 11:59                                     ` Kevin Darbyshire-Bryant
2018-07-02 14:01                                       ` Pete Heist
2018-07-02 12:03                                     ` Toke Høiland-Jørgensen
2018-07-02 14:51                                       ` Pete Heist
2018-07-02 16:14                                         ` Toke Høiland-Jørgensen
2018-07-02 16:59                                           ` Kevin Darbyshire-Bryant
2018-07-02 17:04                                           ` Pete Heist
2018-07-02 17:12                                             ` Kevin Darbyshire-Bryant
2018-07-02 18:24                                             ` Pete Heist
2018-07-02 19:31                                               ` Toke Høiland-Jørgensen
2018-07-02 20:09                                                 ` Pete Heist
2018-07-02 20:11                                                   ` Toke Høiland-Jørgensen
2018-07-02 20:46                                                     ` Pete Heist
     [not found]                                           ` <mailman.407.1530550780.3512.cake@lists.bufferbloat.net>
2018-07-02 17:50                                             ` Kevin Darbyshire-Bryant
2018-07-02 19:33                                               ` Toke Høiland-Jørgensen
2018-07-02 19:36                                                 ` Kevin Darbyshire-Bryant
2018-07-02 19:39                                                   ` Toke Høiland-Jørgensen
2018-07-02 20:03                                                     ` [Cake] cake at 60gbit Dave Taht
2018-07-02 20:09                                                       ` Toke Høiland-Jørgensen
2018-07-02 21:16                                                         ` Pete Heist
2018-07-02 21:35                                                           ` Toke Høiland-Jørgensen
2018-07-02 22:07                                                             ` Georgios Amanakis
2018-07-02 22:12                                                               ` Dave Taht
2018-07-02 23:48                                                                 ` Georgios Amanakis
2018-07-02 22:23                                                               ` Toke Høiland-Jørgensen
2018-07-03  7:35                                                                 ` Pete Heist
2018-07-03  9:18                                                                 ` Jonathan Morton
2018-07-03  9:57                                                                   ` Pete Heist
2018-07-03 10:27                                                                   ` Toke Høiland-Jørgensen
2018-07-03 10:41                                                                     ` Pete Heist
2018-07-05 22:31                                                                     ` Toke Høiland-Jørgensen
2018-07-05 23:48                                                                       ` Georgios Amanakis [this message]
2018-07-06  1:21                                                                         ` Dave Taht
2018-07-06  2:55                                                                           ` George Amanakis
2018-07-06  3:06                                                                             ` George Amanakis
2018-07-06  9:22                                                                               ` Toke Høiland-Jørgensen
2018-07-06  9:21                                                                           ` Toke Høiland-Jørgensen
2018-07-06  8:55                                                                       ` Pete Heist
2018-07-06  9:29                                                                         ` Toke Høiland-Jørgensen
2018-07-06 10:00                                                                           ` Pete Heist
2018-07-06 10:46                                                                             ` Toke Høiland-Jørgensen
2018-07-06 11:33                                                                               ` Toke Høiland-Jørgensen
2018-07-06 11:43                                                                                 ` Jonathan Morton
2018-07-06 11:48                                                                                   ` Toke Høiland-Jørgensen
2018-07-06 11:58                                                                                 ` Pete Heist
2018-07-06 12:04                                                                                   ` Toke Høiland-Jørgensen
2018-07-02 18:39                                           ` [Cake] Cake on openwrt - falling behind Dave Taht
2018-07-02 19:11                                             ` Kevin Darbyshire-Bryant
2018-07-02 19:23                                               ` Toke Høiland-Jørgensen
2018-07-02 19:27                                                 ` Dave Taht
2018-07-02 19:38                                                   ` Toke Høiland-Jørgensen
2018-07-02 20:05                                                     ` Toke Høiland-Jørgensen
2018-07-02 19:31                                             ` Pete Heist
     [not found]                               ` <mailman.397.1530474091.3512.cake@lists.bufferbloat.net>
2018-07-01 23:55                                 ` Dave Taht
2018-07-02  0:05                                   ` Dave Taht
     [not found]                           ` <mailman.392.1530455913.3512.cake@lists.bufferbloat.net>
2018-07-01 15:17                             ` Jonathan Morton
     [not found]       ` <mailman.384.1530384918.3512.cake@lists.bufferbloat.net>
2018-07-01  9:46         ` Magnus Olsson
2018-07-01 12:34           ` Kevin Darbyshire-Bryant

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