From: Zh-yuan Ye ye.zh-yuan@socionext.com
[ Upstream commit 961d0e5b32946703125964f9f5b6321d60f4d706 ]
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: 585d763af09c ("net/sched: Introduce Credit Based Shaper (CBS) qdisc") Signed-off-by: Zh-yuan Ye ye.zh-yuan@socionext.com Reviewed-by: Vinicius Costa Gomes vinicius.gomes@intel.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sched/sch_cbs.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
--- a/net/sched/sch_cbs.c +++ b/net/sched/sch_cbs.c @@ -181,6 +181,11 @@ static struct sk_buff *cbs_dequeue_soft( 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( 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; }