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Date:   Wed, 16 Sep 2020 23:05:33 -0700
From:   Xiaoyong Yan <yanxiaoyong5@...il.com>
To:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Xiaoyong Yan <yanxiaoyong5@...il.com>
Subject: [PATCH] [PATCH] net/sched : cbs : fix calculation error of idleslope credits

in the function cbs_dequeue_soft, when q->credits <0, [now - q->last]
should be accounted for sendslope,not idleslope.

so the solution as follows: when q->credits is less than 0, directly
calculate delay time, activate hrtimer and when hrtimer fires,
calculate idleslope credits and update it to q->credits.

because of the lack of self-defined qdisc_watchdog_func, so in the
generic sch_api, add qdisc_watchdog_init_func and
qdisc_watchdog_init_clockid_func, so sch_cbs can use it to define its
own process.

the patch is changed based on v5.4.42,and the test result as follows:
the NIC is 100Mb/s ,full duplex.

step1:
tc qdisc add dev ens33 root cbs idleslope 75 sendslope -25 hicredit 1000000 locredit -1000000 offload 0
step2:
root@...ntu:/home/yxy/kernel/linux-stable# iperf -c 192.168.1.114 -i 1
------------------------------------------------------------
Client connecting to 192.168.1.114, TCP port 5001
TCP window size:  246 KByte (default)
------------------------------------------------------------
[  3] local 192.168.1.120 port 42004 connected with 192.168.1.114 port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 1.0 sec  9.00 MBytes  75.5 Mbits/sec
[  3]  1.0- 2.0 sec  8.50 MBytes  71.3 Mbits/sec
[  3]  2.0- 3.0 sec  8.50 MBytes  71.3 Mbits/sec
[  3]  3.0- 4.0 sec  8.38 MBytes  70.3 Mbits/sec
[  3]  4.0- 5.0 sec  8.38 MBytes  70.3 Mbits/sec
[  3]  5.0- 6.0 sec  8.50 MBytes  71.3 Mbits/sec
[  3]  6.0- 7.0 sec  8.50 MBytes  71.3 Mbits/sec
[  3]  7.0- 8.0 sec  8.62 MBytes  72.4 Mbits/sec
[  3]  8.0- 9.0 sec  8.50 MBytes  71.3 Mbits/sec
[  3]  9.0-10.0 sec  8.62 MBytes  72.4 Mbits/sec
[  3]  0.0-10.0 sec  85.5 MBytes  71.5 Mbits/sec

Signed-off-by: Xiaoyong Yan <yanxiaoyong5@...il.com>
---
 include/net/pkt_sched.h |  7 +++++++
 net/sched/sch_api.c     | 20 ++++++++++++++++++--
 net/sched/sch_cbs.c     | 41 +++++++++++++++++++++++++----------------
 3 files changed, 50 insertions(+), 18 deletions(-)

diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 6a70845bd9ab..5fec23b15e1c 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -9,6 +9,7 @@
 #include <net/sch_generic.h>
 #include <net/net_namespace.h>
 #include <uapi/linux/pkt_sched.h>
+#include <linux/hrtimer.h>

#define DEFAULT_TX_QUEUE_LEN	1000

@@ -72,6 +73,12 @@ struct qdisc_watchdog {
 	struct Qdisc	*qdisc;
 };

+typedef enum hrtimer_restart (*qdisc_watchdog_func_t)(struct hrtimer *timer);
+void qdisc_watchdog_init_clockid_func(struct qdisc_watchdog *wd, struct Qdisc *qdisc,
+		 clockid_t clockid,qdisc_watchdog_func_t func);
+void qdisc_watchdog_init_func(struct qdisc_watchdog *wd,struct Qdisc *qdisc,qdisc_watchdog_func_t func);
+enum hrtimer_restart qdisc_watchdog(struct hrtimer *timer);
+
 void qdisc_watchdog_init_clockid(struct qdisc_watchdog *wd, struct Qdisc *qdisc,
 				 clockid_t clockid);
 void qdisc_watchdog_init(struct qdisc_watchdog *wd, struct Qdisc *qdisc);
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 50794125bf02..fea08d10c811 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -22,7 +22,6 @@
 #include <linux/seq_file.h>
 #include <linux/kmod.h>
 #include <linux/list.h>
-#include <linux/hrtimer.h>
 #include <linux/slab.h>
 #include <linux/hashtable.h>

@@ -591,7 +590,7 @@ void qdisc_warn_nonwc(const char *txt, struct Qdisc *qdisc)
 }
 EXPORT_SYMBOL(qdisc_warn_nonwc);

-static enum hrtimer_restart qdisc_watchdog(struct hrtimer *timer)
+enum hrtimer_restart qdisc_watchdog(struct hrtimer *timer)
 {
 	struct qdisc_watchdog *wd = container_of(timer, struct qdisc_watchdog,
 						 timer);
@@ -602,7 +601,24 @@ static enum hrtimer_restart qdisc_watchdog(struct hrtimer *timer)

 	return HRTIMER_NORESTART;
 }
+EXPORT_SYMBOL(qdisc_watchdog);

+void qdisc_watchdog_init_clockid_func(struct qdisc_watchdog *wd,struct Qdisc *qdisc,clockid_t clockid,qdisc_watchdog_func_t func)
+{
+	hrtimer_init(&wd->timer,clockid,HRTIMER_MODE_ABS_PINNED);
+	if(!func)
+		wd->timer.function = qdisc_watchdog;
+	else
+		wd->timer.function = func;
+	wd->qdisc = qdisc;
+}
+EXPORT_SYMBOL(qdisc_watchdog_init_clockid_func);
+
+void qdisc_watchdog_init_func(struct qdisc_watchdog *wd,struct Qdisc *qdisc,qdisc_watchdog_func_t func)
+{
+	qdisc_watchdog_init_clockid_func(wd,qdisc,CLOCK_MONOTONIC,func);
+}
+EXPORT_SYMBOL(qdisc_watchdog_init_func);
 void qdisc_watchdog_init_clockid(struct qdisc_watchdog *wd, struct Qdisc *qdisc,
 				 clockid_t clockid)
 {
diff --git a/net/sched/sch_cbs.c b/net/sched/sch_cbs.c
index 2eaac2ff380f..351d3927e107 100644
--- a/net/sched/sch_cbs.c
+++ b/net/sched/sch_cbs.c
@@ -187,21 +187,15 @@ static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch)
 		return NULL;
 	}
 	if (q->credits < 0) {
-		credits = timediff_to_credits(now - q->last, q->idleslope);
+		s64 delay;
+
+		delay = delay_from_credits(q->credits, q->idleslope);
+		qdisc_watchdog_schedule_ns(&q->watchdog, now + delay);

-		credits = q->credits + credits;
-		q->credits = min_t(s64, credits, q->hicredit);
-
-		if (q->credits < 0) {
-			s64 delay;
-
-			delay = delay_from_credits(q->credits, q->idleslope);
-			qdisc_watchdog_schedule_ns(&q->watchdog, now + delay);
-
-			q->last = now;
+		q->last = now;

-			return NULL;
-		}
+		return NULL;
+
 	}
 	skb = cbs_child_dequeue(sch, qdisc);
 	if (!skb)
@@ -212,11 +206,12 @@ static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch)
 	/* As sendslope is a negative number, this will decrease the
 	 * amount of q->credits.
 	 */
+
 	credits = credits_from_len(len, q->sendslope,
 				   atomic64_read(&q->port_rate));
 	credits += q->credits;

-	q->credits = max_t(s64, credits, q->locredit);
+	q->credits = clamp_t(s64, credits, q->locredit,q->hicredit);
 	/* Estimate of the transmission of the last byte of the packet in ns */
 	if (unlikely(atomic64_read(&q->port_rate) == 0))
 		q->last = now;
@@ -323,7 +318,7 @@ static void cbs_set_port_rate(struct net_device *dev, struct cbs_sched_data *q)
 	port_rate = speed * 1000 * BYTES_PER_KBIT;

 	atomic64_set(&q->port_rate, port_rate);
-	netdev_dbg(dev, "cbs: set %s's port_rate to: %lld, linkspeed: %d\n",
+	netdev_dbg(dev,"cbs: set %s's port_rate to: %lld, linkspeed: %d\n",
 		   dev->name, (long long)atomic64_read(&q->port_rate),
 		   ecmd.base.speed);
 }
@@ -396,7 +391,21 @@ static int cbs_change(struct Qdisc *sch, struct nlattr *opt,

 	return 0;
 }
+static enum hrtimer_restart cbs_qdisc_watchdog(struct hrtimer *timer)
+{
+	struct qdisc_watchdog *wd = container_of(timer,struct qdisc_watchdog,timer);
+	struct Qdisc *sch = wd->qdisc;
+	struct cbs_sched_data *q = qdisc_priv(sch);
+	s64 now = ktime_get_ns();
+	s64 credits;
+
+	credits  = timediff_to_credits(now-q->last,q->idleslope);
+	credits = q->credits+credits;
+	q->credits = clamp_t(s64,credits,q->locredit,q->hicredit);
+	q->last = now;

+	return qdisc_watchdog(timer);
+}
 static int cbs_init(struct Qdisc *sch, struct nlattr *opt,
 		    struct netlink_ext_ack *extack)
 {
@@ -424,7 +433,7 @@ static int cbs_init(struct Qdisc *sch, struct nlattr *opt,
 	q->enqueue = cbs_enqueue_soft;
 	q->dequeue = cbs_dequeue_soft;

-	qdisc_watchdog_init(&q->watchdog, sch);
+	qdisc_watchdog_init_func(&q->watchdog, sch,cbs_qdisc_watchdog);

 	return cbs_change(sch, opt, extack);
 }
--
2.25.1

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