netdev - Re: [PATCH net-next] fq_codel: add memory limitation per queue

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Date:	Sun, 8 May 2016 21:14:13 -0700
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	Jesper Dangaard Brouer <brouer@...hat.com>,
	Dave Täht <dave.taht@...il.com>,
	netdev <netdev@...r.kernel.org>, moeller0 <moeller0@....de>
Subject: Re: [PATCH net-next] fq_codel: add memory limitation per queue

On Fri, May 6, 2016 at 8:55 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> @@ -193,6 +199,7 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch)
>         unsigned int idx, prev_backlog, prev_qlen;
>         struct fq_codel_flow *flow;
>         int uninitialized_var(ret);
> +       bool memory_limited;
>
>         idx = fq_codel_classify(skb, sch, &ret);
>         if (idx == 0) {
> @@ -215,7 +222,9 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch)
>                 flow->deficit = q->quantum;
>                 flow->dropped = 0;
>         }
> -       if (++sch->q.qlen <= sch->limit)
> +       q->memory_usage += skb->truesize;
> +       memory_limited = q->memory_usage > q->memory_limit;
> +       if (++sch->q.qlen <= sch->limit && !memory_limited)
>                 return NET_XMIT_SUCCESS;
>
>         prev_backlog = sch->qstats.backlog;
> @@ -229,7 +238,8 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch)
>         ret = fq_codel_drop(sch, q->drop_batch_size);
>
>         q->drop_overlimit += prev_qlen - sch->q.qlen;
> -
> +       if (memory_limited)
> +               q->drop_overmemory += prev_qlen - sch->q.qlen;

So when the packet is dropped due to memory over limit, should
we return failure for this case? Or I miss anything?