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| author | Eric Dumazet <edumazet@google.com> | 2016-06-04 12:55:13 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-06-07 14:49:56 -0700 |
| commit | 80e509db54c81247b32fcb75bb1730fc789b893d (patch) | |
| tree | 6252613ac72781d36051be76b3248cce6f9c3e9a /net/sched | |
| parent | 5b6c1b4d46b0dae4edea636a776d09f2064f4cd7 (diff) | |
| download | lwn-80e509db54c81247b32fcb75bb1730fc789b893d.tar.gz lwn-80e509db54c81247b32fcb75bb1730fc789b893d.zip | |
fq_codel: fix NET_XMIT_CN behavior
My prior attempt to fix the backlogs of parents failed.
If we return NET_XMIT_CN, our parents wont increase their backlog,
so our qdisc_tree_reduce_backlog() should take this into account.
v2: Florian Westphal pointed out that we could drop the packet,
so we need to save qdisc_pkt_len(skb) in a temp variable before
calling fq_codel_drop()
Fixes: 9d18562a2278 ("fq_codel: add batch ability to fq_codel_drop()")
Fixes: 2ccccf5fb43f ("net_sched: update hierarchical backlog too")
Reported-by: Stas Nichiporovich <stasn77@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched')
| -rw-r--r-- | net/sched/sch_fq_codel.c | 24 |
1 files changed, 18 insertions, 6 deletions
diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c index 6883a8971562..fff7867f4a4f 100644 --- a/net/sched/sch_fq_codel.c +++ b/net/sched/sch_fq_codel.c @@ -199,6 +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); + unsigned int pkt_len; bool memory_limited; idx = fq_codel_classify(skb, sch, &ret); @@ -230,6 +231,8 @@ static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch) prev_backlog = sch->qstats.backlog; prev_qlen = sch->q.qlen; + /* save this packet length as it might be dropped by fq_codel_drop() */ + pkt_len = qdisc_pkt_len(skb); /* fq_codel_drop() is quite expensive, as it performs a linear search * in q->backlogs[] to find a fat flow. * So instead of dropping a single packet, drop half of its backlog @@ -237,14 +240,23 @@ 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; + prev_qlen -= sch->q.qlen; + prev_backlog -= sch->qstats.backlog; + q->drop_overlimit += prev_qlen; if (memory_limited) - q->drop_overmemory += prev_qlen - sch->q.qlen; - /* As we dropped packet(s), better let upper stack know this */ - qdisc_tree_reduce_backlog(sch, prev_qlen - sch->q.qlen, - prev_backlog - sch->qstats.backlog); + q->drop_overmemory += prev_qlen; - return ret == idx ? NET_XMIT_CN : NET_XMIT_SUCCESS; + /* As we dropped packet(s), better let upper stack know this. + * If we dropped a packet for this flow, return NET_XMIT_CN, + * but in this case, our parents wont increase their backlogs. + */ + if (ret == idx) { + qdisc_tree_reduce_backlog(sch, prev_qlen - 1, + prev_backlog - pkt_len); + return NET_XMIT_CN; + } + qdisc_tree_reduce_backlog(sch, prev_qlen, prev_backlog); + return NET_XMIT_SUCCESS; } /* This is the specific function called from codel_dequeue() |