diff mbox series

[net,v2] net: cbs: Fix software cbs to consider packet sending time

Message ID 20200323061709.1881-1-ye.zh-yuan@socionext.com
State New
Headers show
Series [net,v2] net: cbs: Fix software cbs to consider packet sending time | expand

Commit Message

Zh-yuan Ye March 23, 2020, 6:17 a.m. UTC 
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.

Signed-off-by: Zh-yuan Ye <ye.zh-yuan@socionext.com>

---
changes in v2:
 - combine variable "send_completed" into "last"
 - add the comment for estimate of the packet sending

---
 net/sched/sch_cbs.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/net/sched/sch_cbs.c b/net/sched/sch_cbs.c
index b2905b03a432..20f95f0b9d5b 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);
 
@@ -192,7 +197,6 @@  static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch)
 
 			delay = delay_from_credits(q->credits, q->idleslope);
 			qdisc_watchdog_schedule_ns(&q->watchdog, now + delay);
-
 			q->last = now;
 
 			return NULL;
@@ -212,7 +216,9 @@  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 */
+	q->last = now + div64_s64(len * NSEC_PER_SEC,
+				  atomic64_read(&q->port_rate));
 
 	return skb;
 }