netdev - Re: [PATCH] net_sched/hhf: update hierarchical backlog when drop packet

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Date:   Mon, 21 Aug 2017 09:52:12 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jiri Pirko <jiri@...nulli.us>
Subject: Re: [PATCH] net_sched/hhf: update hierarchical backlog when drop packet

On Mon, Aug 21, 2017 at 1:12 AM, Konstantin Khlebnikov
<khlebnikov@...dex-team.ru> wrote:
> When hhf_enqueue() drops packet from another bucket it
> have to update backlog at upper qdiscs too.
>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> Fixes: 2ccccf5fb43f ("net_sched: update hierarchical backlog too")
> ---
>  net/sched/sch_hhf.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/net/sched/sch_hhf.c b/net/sched/sch_hhf.c
> index 51d3ba682af9..c8d84436e427 100644
> --- a/net/sched/sch_hhf.c
> +++ b/net/sched/sch_hhf.c
> @@ -406,8 +406,11 @@ static int hhf_enqueue(struct sk_buff *skb, struct Qdisc *sch,
>         /* Return Congestion Notification only if we dropped a packet from this
>          * bucket.
>          */
> -       if (hhf_drop(sch, to_free) == idx)
> +       if (hhf_drop(sch, to_free) == idx) {
> +               qdisc_tree_reduce_backlog(sch, 0,


It should be 1 here instead of 0, because one packet is dropped
even if hhf_drop() == idx.


> +                                         prev_backlog - sch->qstats.backlog);
>                 return NET_XMIT_CN;
> +       }
>
>         /* As we dropped a packet, better let upper stack know this. */
>         qdisc_tree_reduce_backlog(sch, 1, prev_backlog - sch->qstats.backlog);
>