From: Eric Dumazet <eduma...@google.com>
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 <stas...@gmail.com>
Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: WANG Cong <xiyou.wangc...@gmail.com>
Cc: Jamal Hadi Salim <j...@mojatatu.com>
---
net/sched/sch_fq_codel.c | 24 ++++++++++++++++++------
1 file 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()
