From 53e2126a242f4ff6505e3442ebe784a0ebfc61cf Mon Sep 17 00:00:00 2001 From: Zh-yuan Ye Date: Tue, 24 Mar 2020 17:28:25 +0900 Subject: [PATCH] net: cbs: Fix software cbs to consider packet sending time Currently the software CBS does not consider the packet sending time when depleting the credits. It caused the throughput to be Idleslope[kbps] * (Port transmit rate[kbps] / |Sendslope[kbps]|) where Idleslope * (Port transmit rate / (Idleslope + |Sendslope|)) = Idleslope is expected. In order to fix the issue above, this patch takes the time when the packet sending completes into account by moving the anchor time variable "last" ahead to the send completion time upon transmission and adding wait when the next dequeue request comes before the send completion time of the previous packet. changelog: V2->V3: - remove unnecessary whitespace cleanup - add the checks if port_rate is 0 before division V1->V2: - combine variable "send_completed" into "last" - add the comment for estimate of the packet sending Fixes: 92c6bd6c8cc7 ("net/sched: Introduce Credit Based Shaper (CBS) qdisc") Signed-off-by: Zh-yuan Ye Reviewed-by: Vinicius Costa Gomes Signed-off-by: David S. Miller --- net/sched/sch_cbs.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_cbs.c b/net/sched/sch_cbs.c index b2905b03a432f..2eaac2ff380fa 100644 --- a/net/sched/sch_cbs.c +++ b/net/sched/sch_cbs.c @@ -181,6 +181,11 @@ static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch) s64 credits; int len; + /* The previous packet is still being sent */ + if (now < q->last) { + qdisc_watchdog_schedule_ns(&q->watchdog, q->last); + return NULL; + } if (q->credits < 0) { credits = timediff_to_credits(now - q->last, q->idleslope); @@ -212,7 +217,12 @@ static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch) credits += q->credits; q->credits = max_t(s64, credits, q->locredit); - q->last = now; + /* Estimate of the transmission of the last byte of the packet in ns */ + if (unlikely(atomic64_read(&q->port_rate) == 0)) + q->last = now; + else + q->last = now + div64_s64(len * NSEC_PER_SEC, + atomic64_read(&q->port_rate)); return skb; } -- 2.39.5