Message-ID: <28bff9d7-fa2d-5284-f6d5-e08cd792c9c6@alibaba-inc.com>
Date:   Tue, 07 Jul 2020 02:08:13 +0800
From:   "YU, Xiangning" <xiangning.yu@...baba-inc.com>
To:     netdev@...r.kernel.org
Subject: [PATCH net-next 2/2] net: sched: Lockless Token Bucket (LTB) Qdisc

Lockless Token Bucket (LTB) is a qdisc implementation that controls the
use of outbound bandwidth on a shared link. With the help of lockless
qdisc, and by decoupling rate limiting and bandwidth sharing, LTB is
designed to scale in the cloud data centers.

Signed-off-by: Xiangning Yu <xiangning.yu@...baba-inc.com>
---
 include/uapi/linux/pkt_sched.h |   35 ++
 net/sched/Kconfig              |   12 +
 net/sched/Makefile             |    1 +
 net/sched/sch_ltb.c            | 1280 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 1328 insertions(+)
 create mode 100644 net/sched/sch_ltb.c

diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 9e7c2c6..310a627 100644
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h
@@ -447,6 +447,41 @@ struct tc_htb_xstats {
 	__s32 ctokens;
 };
 
+/* LTB section */
+
+#define TC_LTB_PROTOVER	3 /* the same as LTB and TC's major */
+#define TC_LTB_NUMPRIO	16
+enum {
+	TCA_LTB_UNSPEC,
+	TCA_LTB_PARMS,
+	TCA_LTB_INIT,
+	TCA_LTB_RATE64,
+	TCA_LTB_CEIL64,
+	TCA_LTB_PAD,
+	__TCA_LTB_MAX,
+};
+#define TCA_LTB_MAX (__TCA_LTB_MAX - 1)
+
+struct tc_ltb_opt {
+	struct tc_ratespec rate;
+	struct tc_ratespec ceil;
+	__u64 measured;
+	__u64 allocated;
+	__u64 high_water;
+	__u32 prio;
+};
+
+struct tc_ltb_glob {
+	__u32 version;          /* to match LTB/TC */
+	__u32 defcls;           /* default class number */
+};
+
+struct tc_ltb_xstats {
+	__u64 measured;
+	__u64 allocated;
+	__u64 high_water;
+};
+
 /* HFSC section */
 
 struct tc_hfsc_qopt {
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index a3b37d8..9a8adb6 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -76,6 +76,18 @@ config NET_SCH_HTB
 	  To compile this code as a module, choose M here: the
 	  module will be called sch_htb.
 
+config NET_SCH_LTB
+	tristate "Lockless Token Bucket (LTB)"
+	help
+	  Say Y here if you want to use the Lockless Token Buckets (LTB)
+	  packet scheduling algorithm.
+
+	  LTB is very similar to HTB regarding its goals however is has
+	  different implementation and different algorithm.
+
+	  To compile this code as a module, choose M here: the
+	  module will be called sch_ltb.
+
 config NET_SCH_HFSC
 	tristate "Hierarchical Fair Service Curve (HFSC)"
 	help
diff --git a/net/sched/Makefile b/net/sched/Makefile
index 66bbf9a..6caa34d 100644
--- a/net/sched/Makefile
+++ b/net/sched/Makefile
@@ -34,6 +34,7 @@ obj-$(CONFIG_NET_ACT_GATE)	+= act_gate.o
 obj-$(CONFIG_NET_SCH_FIFO)	+= sch_fifo.o
 obj-$(CONFIG_NET_SCH_CBQ)	+= sch_cbq.o
 obj-$(CONFIG_NET_SCH_HTB)	+= sch_htb.o
+obj-$(CONFIG_NET_SCH_LTB)	+= sch_ltb.o
 obj-$(CONFIG_NET_SCH_HFSC)	+= sch_hfsc.o
 obj-$(CONFIG_NET_SCH_RED)	+= sch_red.o
 obj-$(CONFIG_NET_SCH_GRED)	+= sch_gred.o
diff --git a/net/sched/sch_ltb.c b/net/sched/sch_ltb.c
new file mode 100644
index 0000000..494b15f
--- /dev/null
+++ b/net/sched/sch_ltb.c
@@ -0,0 +1,1280 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* net/sched/sch_ltb.c Lockless Token Bucket.
+ *
+ * Authors:	Xiangning Yu <xiangning.yu@...baba-inc.com>
+ *		Ke Ma <k.ma@...baba-inc.com>
+ *		Jianjun Duan <jianjun.duan@...baba-inc.com>
+ *		Kun Liu <shubo.lk@...baba-inc.com>
+ */
+#include <linux/moduleparam.h>
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/skbuff.h>
+#include <linux/list.h>
+#include <linux/compiler.h>
+#include <linux/rbtree.h>
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/ip.h>
+#include <linux/if_vlan.h>
+#include <linux/kthread.h>
+#include <linux/wait.h>
+#include <linux/atomic.h>
+#include <linux/kfifo.h>
+#include <linux/kallsyms.h>
+#include <linux/irq_work.h>
+#include <linux/percpu.h>
+#include <linux/preempt.h>
+#include <linux/hashtable.h>
+#include <linux/vmalloc.h>
+#include <linux/ethtool.h>
+#include <net/ip.h>
+#include <net/netlink.h>
+#include <net/sch_generic.h>
+#include <net/pkt_sched.h>
+
+#define	LTB_VERSION		0x30001
+#define	LTB_CLASS_CONDEMED	1
+#define	HIGH_FREQ_INTERVAL	1000	/* ns */
+#define	LOW_FREQ_INTERVAL	50	/* sampling rate, in ms */
+#define	SHADOW_CLASSID		0
+
+#define	BYTES_PER_JIFF(bps)	((bps) / HZ)
+#define	BYTES_PER_INTERVAL(bps)	(LOW_FREQ_INTERVAL * BYTES_PER_JIFF(bps))
+#define	MINBW			(10 * 1000 * 1000L)
+#define	HIGH_THRESHOLD		80
+#define	SUPPRESS_THRESHOLD	90
+#define	MAX_CPU_COUNT		128	/* make it dynamic */
+#define	SKB_QLEN		512
+#define	NOW()			(jiffies / LOW_FREQ_INTERVAL)
+#define	BPS2MBPS(x)		((x) * 8 / 1000000) /* Bps to Mbps */
+
+static struct Qdisc_ops ltb_pcpu_qdisc_ops;
+
+static const struct nla_policy ltb_policy[TCA_LTB_MAX + 1] = {
+	[TCA_LTB_PARMS]	= { .len = sizeof(struct tc_ltb_opt) },
+	[TCA_LTB_INIT] = { .len = sizeof(struct tc_ltb_glob) },
+	[TCA_LTB_RATE64] = { .type = NLA_U64 },
+	[TCA_LTB_CEIL64] = { .type = NLA_U64 },
+};
+
+struct ltb_class {
+	struct Qdisc_class_common common;
+	struct psched_ratecfg ratecfg;
+	struct psched_ratecfg ceilcfg;
+	u32 prio;
+	struct ltb_class *parent;
+	struct Qdisc *qdisc;
+	struct Qdisc *root_qdisc;
+	u32 classid;
+	struct list_head pnode;
+	unsigned long state; ____cacheline_aligned_in_smp
+
+	/* Aggr/drain context only */
+	s64 next_timestamp; ____cacheline_aligned_in_smp
+	int num_cpus;
+	int last_cpu;
+	s64 bw_used;
+	s64 last_bytes;
+	s64 last_timestamp;
+	s64 stat_bytes;
+	s64 stat_packets;
+	atomic64_t stat_drops;
+
+	/* Balance thread only */
+	s64 rate; ____cacheline_aligned_in_smp
+	s64 ceil;
+	s64 high_water;
+	int drop_delay;
+	s64 bw_allocated;
+	bool want_more;
+
+	/* Shared b/w aggr/drain thread and balancer */
+	unsigned long curr_interval; ____cacheline_aligned_in_smp
+	s64 bw_measured;	/* Measured actual bandwidth */
+	s64 maxbw;	/* Calculated bandwidth */
+
+	STRUCT_KFIFO(struct sk_buff *, SKB_QLEN) aggr_queues[MAX_CPU_COUNT];
+	____cacheline_aligned_in_smp
+	STRUCT_KFIFO(struct sk_buff *, SKB_QLEN * MAX_CPU_COUNT) drain_queue;
+	____cacheline_aligned_in_smp
+	STRUCT_KFIFO(struct sk_buff *, SKB_QLEN) fanout_queues[MAX_CPU_COUNT];
+	____cacheline_aligned_in_smp
+
+	struct tasklet_struct aggr_tasklet;
+	struct hrtimer aggr_timer;
+};
+
+struct ltb_pcpu_data {
+	struct Qdisc *qdisc; ____cacheline_aligned_in_smp
+	bool active;
+};
+
+/* Root qdisc private data */
+struct ltb_sched {
+	struct task_struct *bwbalancer_task;
+	wait_queue_head_t bwbalancer_wq;
+
+	int num_cpus;
+	s64 link_speed;
+	struct Qdisc *root_qdisc;
+	struct net_device *dev;
+
+	struct ltb_pcpu_data *pcpu_data; ____cacheline_aligned_in_smp
+	struct tasklet_struct fanout_tasklet;
+
+	struct ltb_class *default_cls;
+	struct ltb_class *shadow_cls; /* If there is no class created */
+	u32 default_classid;
+
+	rwlock_t prio_rows_lock;
+	struct list_head prio_rows[TC_LTB_NUMPRIO]; /* Priority list */
+	struct Qdisc_class_hash clhash;
+};
+
+/* Per-cpu qdisc private data */
+struct ltb_pcpu_sched {
+	struct ltb_sched *ltb;
+	struct Qdisc *qdisc;
+	int cpu;
+	struct irq_work fanout_irq_work;
+	s64 last_irq_timestamp;
+};
+
+/* The cpu where skb is from */
+struct ltb_skb_cb {
+	int cpu;
+};
+
+static inline struct ltb_skb_cb *ltb_skb_cb(const struct sk_buff *skb)
+{
+	qdisc_cb_private_validate(skb, sizeof(struct ltb_skb_cb));
+	return (struct ltb_skb_cb *)qdisc_skb_cb(skb)->data;
+}
+
+static inline s64 get_linkspeed(struct net_device *dev)
+{
+	struct ethtool_link_ksettings ecmd;
+
+	ASSERT_RTNL();
+	if (netif_running(dev) && !__ethtool_get_link_ksettings(dev, &ecmd))
+		/* Convert to bytes per second */
+		return ecmd.base.speed * 1000 * 1000L / 8;
+	return 0;
+}
+
+static int ltb_update_linkspeed(struct ltb_sched *ltb)
+{
+	s64 linkspeed;
+
+	/* Avoid race with kthread_stop() */
+	if (!rtnl_trylock())
+		return -1;
+
+	linkspeed = get_linkspeed(ltb->dev);
+	if (ltb->link_speed != linkspeed)
+		ltb->link_speed = linkspeed;
+	rtnl_unlock();
+	return 0;
+}
+
+static inline int ltb_drain(struct ltb_class *cl)
+{
+	typeof(&cl->drain_queue) queue;
+	struct sk_buff *skb;
+	int npkts, bytes;
+	unsigned long now = NOW();
+	int cpu;
+	struct ltb_sched *ltb = qdisc_priv(cl->root_qdisc);
+	struct ltb_pcpu_sched *pcpu_q;
+	s64 timestamp;
+	bool need_watchdog = false;
+	struct cpumask cpumask;
+
+	npkts = 0;
+	bytes = 0;
+	cpumask_clear(&cpumask);
+	queue = &cl->drain_queue;
+	while (kfifo_peek(queue, &skb) > 0) {
+		int len = qdisc_pkt_len(skb);
+
+		if (cl->curr_interval != now) {
+			cl->curr_interval = now;
+			timestamp = ktime_get_ns();
+			cl->bw_measured = (cl->stat_bytes - cl->last_bytes) *
+				NSEC_PER_SEC / (timestamp - cl->last_timestamp);
+			cl->last_bytes = cl->stat_bytes;
+			cl->last_timestamp = timestamp;
+			cl->bw_used = 0;
+		} else if (len + cl->bw_used > cl->maxbw) {
+			need_watchdog = true;
+			break;
+		}
+		kfifo_skip(queue);
+		cl->bw_used += len;
+
+		/* Fanout */
+		cpu = ltb_skb_cb(skb)->cpu;
+		ltb_skb_cb(skb)->cpu = 0;
+		if (unlikely(kfifo_put(&cl->fanout_queues[cpu], skb) == 0)) {
+			kfree_skb(skb);
+			atomic64_inc(&cl->stat_drops);
+		} else {
+			/* Account for Generic Segmentation Offload(gso). */
+			cl->stat_bytes += len;
+			cl->stat_packets += skb_is_gso(skb) ?
+			    skb_shinfo(skb)->gso_segs : 1;
+			cpumask_set_cpu(cpu, &cpumask);
+		}
+	}
+
+	for_each_cpu(cpu, &cpumask) {
+		struct Qdisc *q = per_cpu_ptr(ltb->pcpu_data, cpu)->qdisc;
+
+		pcpu_q = (struct ltb_pcpu_sched *)qdisc_priv(q);
+		if (!(q->state & __QDISC_STATE_SCHED) && !qdisc_is_running(q))
+			irq_work_queue_on(&pcpu_q->fanout_irq_work, cpu);
+	}
+
+	return need_watchdog;
+}
+
+static void ltb_aggregate(struct ltb_class *cl)
+{
+	s64 timestamp = ktime_get_ns();
+	struct ltb_sched *ltb = qdisc_priv(cl->root_qdisc);
+	int num_cpus = ltb->num_cpus;
+	int i;
+
+	/* The worker might wake up more often than required */
+	if (cl->next_timestamp > timestamp)
+		/* Try again to keep the pipeline running */
+		goto watchdog;
+
+	cl->next_timestamp = timestamp + HIGH_FREQ_INTERVAL;
+
+	/* Aggregate sk_buff from all CPUs. The memory footprint here should
+	 * be fine because we don't touch each packet.
+	 *
+	 * It's possible to see out of order packets here. While within 1us,
+	 * there won't be too many packets for a single flow, and the Linux
+	 * scheduler is not expected to schedule an application too often
+	 * within this tiny time gap, i.e. 1/1000 jiffes.
+	 */
+	for (i = 0; i < num_cpus; i++) {
+		/* Process CPUs in a round-robin fashion */
+		typeof(&cl->aggr_queues[0]) queue;
+		int queue_len, drain_room;
+		int j;
+
+		queue = &cl->aggr_queues[(i + cl->last_cpu) % num_cpus];
+		queue_len = kfifo_len(queue);
+		drain_room = kfifo_avail(&cl->drain_queue);
+		if (drain_room == 0)
+			break;
+
+		queue_len = queue_len < drain_room ? queue_len : drain_room;
+		for (j = 0; j < queue_len; j++) {
+			struct sk_buff *skb;
+
+			if (kfifo_get(queue, &skb)) {
+				if (unlikely(kfifo_put(&cl->drain_queue,
+						       skb) == 0)) {
+					kfree_skb(skb);
+					atomic64_inc(&cl->stat_drops);
+				}
+			}
+		}
+	}
+	cl->last_cpu++;
+	if (cl->last_cpu == num_cpus)
+		cl->last_cpu = 0;
+
+	if (ltb_drain(cl) == false)
+		return;
+
+watchdog:
+	if (!test_bit(LTB_CLASS_CONDEMED, &cl->state))
+		hrtimer_start(&cl->aggr_timer,
+			      ns_to_ktime(1000 + ktime_get_ns()),
+			      HRTIMER_MODE_ABS_PINNED);
+}
+
+static enum hrtimer_restart ltb_aggr_watchdog(struct hrtimer *timer)
+{
+	struct ltb_class *cl = container_of(timer,
+			     struct ltb_class, aggr_timer);
+
+	if (!test_bit(LTB_CLASS_CONDEMED, &cl->state))
+		tasklet_schedule(&cl->aggr_tasklet);
+
+	return HRTIMER_NORESTART;
+}
+
+static void ltb_aggr_tasklet(unsigned long arg)
+{
+	struct ltb_class *cl = (struct ltb_class *)arg;
+
+	rcu_read_lock_bh();
+	if (!test_bit(LTB_CLASS_CONDEMED, &cl->state))
+		ltb_aggregate(cl);
+	rcu_read_unlock_bh();
+}
+
+static inline void ltb_fanout(struct ltb_sched *ltb)
+{
+	int cpu;
+
+	for (cpu = 0; cpu < ltb->num_cpus; cpu++) {
+		struct Qdisc *q = per_cpu_ptr(ltb->pcpu_data, cpu)->qdisc;
+		struct ltb_pcpu_sched *pcpu_q =
+			(struct ltb_pcpu_sched *)qdisc_priv(q);
+
+		if (q->q.qlen > 0 && !(q->state & __QDISC_STATE_SCHED) &&
+		    !qdisc_is_running(q))
+			irq_work_queue_on(&pcpu_q->fanout_irq_work, cpu);
+	}
+}
+
+static void ltb_fanout_tasklet(unsigned long data)
+{
+	struct ltb_sched *ltb = (struct ltb_sched *)data;
+
+	ltb_fanout(ltb);
+}
+
+static void ltb_fanout_irq_tx_func(struct irq_work *work)
+{
+	struct ltb_pcpu_sched *pcpu_q =
+	    container_of(work, struct ltb_pcpu_sched, fanout_irq_work);
+
+	__netif_schedule(pcpu_q->qdisc);
+}
+
+/* How many classes within the same group want more bandwidth */
+static inline int bw_class_want_more_count(struct list_head *head)
+{
+	int n = 0;
+	struct ltb_class *cl;
+
+	list_for_each_entry(cl, head, pnode) {
+		if (cl->want_more)
+			n++;
+	}
+	return n;
+}
+
+/* Redistribute bandwidth among classes with the same priority */
+static int bw_redistribute_prio(struct list_head *lhead, int bw_available,
+				int n, bool *all_reached_ceil)
+{
+	struct ltb_class *cl;
+	int avg = 0;
+	int orig_bw_allocated;
+	int safe_loop = 0;
+
+	do {
+		if (n > 0)
+			avg = bw_available / n;
+		list_for_each_entry(cl, lhead, pnode) {
+			if (!cl->want_more)
+				continue;
+
+			/* Try to allocate as much as possible */
+			orig_bw_allocated = cl->bw_allocated;
+			cl->bw_allocated = min_t(s64, (cl->bw_allocated + avg),
+						 cl->ceil);
+			/* Significantly larger than high water */
+			if (cl->bw_allocated > cl->high_water * 120 / 100)
+				cl->bw_allocated = cl->high_water;
+			bw_available -= cl->bw_allocated - orig_bw_allocated;
+			if (cl->bw_allocated >= cl->high_water ||
+			    cl->bw_allocated == cl->ceil) {
+				cl->want_more = false;
+				n--;
+			}
+		}
+	} while (bw_available > 0 && n > 0 && safe_loop++ < 2);
+
+	*all_reached_ceil = true;
+	list_for_each_entry(cl, lhead, pnode) {
+		if (cl->bw_allocated != cl->ceil)
+			*all_reached_ceil = false;
+	}
+
+	return bw_available;
+}
+
+static void bw_suppress_lower(struct ltb_sched *ltb, int high)
+{
+	int prio;
+
+	read_lock_bh(&ltb->prio_rows_lock);
+	for (prio = TC_LTB_NUMPRIO - 1; prio > high; prio--) {
+		struct ltb_class *cl;
+
+		list_for_each_entry(cl, &ltb->prio_rows[prio], pnode) {
+			if (cl->bw_allocated > cl->rate) {
+				cl->bw_allocated = max_t(s64,
+							 cl->bw_measured *
+							 90 / 100, cl->rate);
+			}
+		}
+	}
+	read_unlock_bh(&ltb->prio_rows_lock);
+}
+
+static int bw_redistribute(struct ltb_sched *ltb, int bw_available)
+{
+	int prio = 0;
+	int n;
+	int highest_non_saturated_prio = TC_LTB_NUMPRIO;
+	bool all_reached_ceil;
+
+	read_lock_bh(&ltb->prio_rows_lock);
+	for (; prio < TC_LTB_NUMPRIO; prio++) {
+		struct list_head *head = &ltb->prio_rows[prio];
+
+		all_reached_ceil = true;
+
+		n = bw_class_want_more_count(head);
+		bw_available = bw_redistribute_prio(head, bw_available,
+						    n, &all_reached_ceil);
+		if (!all_reached_ceil && highest_non_saturated_prio > prio)
+			highest_non_saturated_prio = prio;
+
+		if (bw_available < 0)
+			break;
+	}
+	read_unlock_bh(&ltb->prio_rows_lock);
+	return highest_non_saturated_prio;
+}
+
+static void bw_sync_all(struct ltb_sched *ltb, int bw_available,
+			int is_light_traffic)
+{
+	struct ltb_class *cl;
+	int i;
+
+	for (i = 0; i < ltb->clhash.hashsize; i++) {
+		hlist_for_each_entry_rcu(cl, &ltb->clhash.hash[i],
+					 common.hnode) {
+			if (cl->classid == SHADOW_CLASSID)
+				continue;
+
+			if (is_light_traffic)
+				cl->bw_allocated = min_t(s64, cl->ceil,
+							 cl->bw_allocated +
+							 bw_available);
+			cl->maxbw = BYTES_PER_INTERVAL((s64)cl->bw_allocated);
+			/* Maxbw will be visiable eventually. */
+			smp_mb();
+		}
+	}
+}
+
+static void bw_balance(struct ltb_sched *ltb)
+{
+	struct ltb_class *cl;
+	s64 link_speed = ltb->link_speed;
+	int bw_available = link_speed;
+	s64 total = 0;
+	int high = TC_LTB_NUMPRIO;
+	int is_light_traffic = 1;
+	int i;
+
+	if (unlikely(link_speed <= 0))
+		return;
+
+	for (i = 0; i < ltb->clhash.hashsize; i++) {
+		hlist_for_each_entry_rcu(cl, &ltb->clhash.hash[i],
+					 common.hnode) {
+			if (cl->classid == SHADOW_CLASSID)
+				continue;
+
+			/* It's been a while the bw measurement has stopped */
+			if (NOW() - cl->curr_interval > 2 &&
+			    cl->bw_measured != 0)
+				cl->bw_measured = 0;
+
+			if (cl->bw_measured > cl->high_water * 95 / 100) {
+				/* Increase */
+				if (cl->high_water < cl->rate)
+					cl->high_water = min_t(s64,
+							       cl->high_water *
+							       2, cl->rate);
+				else
+					cl->high_water =
+					    cl->high_water * 120 / 100;
+				cl->high_water = min_t(s64, cl->ceil,
+						       cl->high_water);
+				if (cl->drop_delay != 0)
+					cl->drop_delay = 0;
+			} else if (cl->bw_measured <
+			    cl->high_water * 85 / 100) {
+				/* Drop */
+				cl->drop_delay++;
+				if (cl->drop_delay == 5) {
+					cl->high_water =
+					    cl->bw_measured * 110 / 100;
+					cl->drop_delay = 0;
+				}
+			} else {
+				/* Stable */
+				cl->high_water = cl->bw_allocated;
+				if (cl->drop_delay != 0)
+					cl->drop_delay = 0;
+			}
+
+			cl->high_water = max_t(s64, cl->high_water, MINBW);
+			cl->bw_allocated = min_t(s64, cl->rate, cl->high_water);
+			bw_available -= cl->bw_allocated;
+			if (cl->bw_allocated < cl->high_water)
+				cl->want_more = true;
+			else
+				cl->want_more = false;
+			total += cl->bw_measured;
+		}
+	}
+
+	if (total > HIGH_THRESHOLD * ltb->link_speed / 100) {
+		is_light_traffic  = 0;
+
+		/* Redistribute the remaining bandwidth by priority
+		 */
+		if (bw_available > 0)
+			high = bw_redistribute(ltb, bw_available);
+
+		/* The link is near satuarated, we need to suppress
+		 * those classes that:
+		 *	- are not of the highest priority that haven't
+		 *	reached all ceiling.
+		 *	- consume more than rate.
+		 *
+		 * This will give the higher priority class a better chance
+		 * to gain full speed.
+		 */
+		if (total > SUPPRESS_THRESHOLD * ltb->link_speed / 100)
+			bw_suppress_lower(ltb, high);
+	}
+	bw_sync_all(ltb, bw_available, is_light_traffic);
+}
+
+static int ltb_bw_balancer_kthread(void *arg)
+{
+	struct ltb_sched *ltb = (struct ltb_sched *)arg;
+
+	for (;;) {
+		wait_event_interruptible_timeout(ltb->bwbalancer_wq,
+						 kthread_should_stop(),
+						 LOW_FREQ_INTERVAL);
+		if (kthread_should_stop())
+			break;
+
+		if (ltb_update_linkspeed(ltb) != 0)
+			continue;
+
+		rcu_read_lock_bh();
+		bw_balance(ltb);
+		rcu_read_unlock_bh();
+	}
+	return 0;
+}
+
+static int ltb_parse_opts(struct nlattr *opt, u32 *defcls)
+{
+	struct nlattr *tb[TCA_LTB_MAX + 1];
+	struct tc_ltb_glob *gopt;
+	int err;
+
+	err = nla_parse_nested_deprecated(tb, TCA_LTB_MAX, opt,
+					  ltb_policy, NULL);
+	if (err < 0)
+		return err;
+
+	if (!tb[TCA_LTB_INIT])
+		return -EINVAL;
+
+	gopt = nla_data(tb[TCA_LTB_INIT]);
+	if (gopt->version != LTB_VERSION >> 16)
+		return -EINVAL;
+
+	if (defcls)
+		*defcls = gopt->defcls;
+	return 0;
+}
+
+static int ltb_pcpu_init(struct Qdisc *sch, struct nlattr *opt,
+			 struct netlink_ext_ack *extack)
+{
+	struct ltb_pcpu_sched *pcpu_q =
+		(struct ltb_pcpu_sched *)qdisc_priv(sch);
+
+	memset(pcpu_q, 0, sizeof(*pcpu_q));
+	pcpu_q->qdisc = sch;
+	init_irq_work(&pcpu_q->fanout_irq_work, ltb_fanout_irq_tx_func);
+	return 0;
+}
+
+static struct sk_buff *ltb_pcpu_class_dequeue(struct ltb_pcpu_sched *pcpu_q,
+					      struct ltb_class *cl)
+{
+	struct sk_buff *skb;
+	typeof(&cl->fanout_queues[0]) queue;
+
+	queue = &cl->fanout_queues[pcpu_q->cpu];
+	if (kfifo_peek(queue, &skb) > 0) {
+		kfifo_skip(queue);
+		pcpu_q->qdisc->q.qlen--;
+		return skb;
+	}
+
+	return NULL;
+}
+
+static struct sk_buff *ltb_pcpu_dequeue(struct Qdisc *sch)
+{
+	struct ltb_sched *ltb;
+	struct ltb_pcpu_sched *pcpu_q;
+	struct ltb_class *cl;
+	struct sk_buff *skb;
+	int i;
+
+	pcpu_q = (struct ltb_pcpu_sched *)qdisc_priv(sch);
+	ltb = pcpu_q->ltb;
+
+	for (i = 0; i < ltb->clhash.hashsize; i++) {
+		hlist_for_each_entry(cl, &ltb->clhash.hash[i], common.hnode) {
+			skb = ltb_pcpu_class_dequeue(pcpu_q, cl);
+			if (skb)
+				return skb;
+		}
+	}
+	return NULL;
+}
+
+static inline struct ltb_class *ltb_find_class(struct Qdisc *sch, u32 handle)
+{
+	struct ltb_sched *q = qdisc_priv(sch);
+	struct Qdisc_class_common *clc;
+
+	clc = qdisc_class_find(&q->clhash, handle);
+	if (!clc)
+		return NULL;
+
+	return container_of(clc, struct ltb_class, common);
+}
+
+static struct ltb_class *ltb_alloc_class(struct Qdisc *sch,
+					 struct ltb_class *parent, u32 classid,
+					 struct psched_ratecfg *ratecfg,
+					 struct psched_ratecfg *ceilcfg,
+					 u32 prio)
+{
+	struct ltb_sched *ltb  = qdisc_priv(sch);
+	struct ltb_class *cl;
+	int i;
+
+	if (ratecfg->rate_bytes_ps > ceilcfg->rate_bytes_ps ||
+	    prio < 0 || prio >= TC_LTB_NUMPRIO)
+		return NULL;
+
+	cl = kzalloc(sizeof(*cl), GFP_KERNEL);
+	if (!cl)
+		return NULL;
+
+	cl->common.classid = classid;
+	cl->parent = parent;
+	cl->ratecfg = *ratecfg;
+	cl->ceilcfg = *ceilcfg;
+	cl->prio = prio;
+	cl->classid = classid;
+	cl->root_qdisc = sch;
+	cl->num_cpus = ltb->num_cpus;
+	cl->last_cpu = 0;
+	cl->ceil = ceilcfg->rate_bytes_ps;
+	cl->rate = ratecfg->rate_bytes_ps;
+	cl->bw_allocated = ratecfg->rate_bytes_ps;
+	cl->high_water = cl->bw_allocated * 110 / 100;
+	cl->maxbw = BYTES_PER_INTERVAL((s64)ratecfg->rate_bytes_ps);
+
+	INIT_KFIFO(cl->drain_queue);
+	for (i = 0; i < cl->num_cpus; i++) {
+		INIT_KFIFO(cl->aggr_queues[i]);
+		INIT_KFIFO(cl->fanout_queues[i]);
+	}
+	hrtimer_init(&cl->aggr_timer, CLOCK_MONOTONIC,
+		     HRTIMER_MODE_ABS_PINNED);
+	cl->aggr_timer.function = ltb_aggr_watchdog;
+	tasklet_init(&cl->aggr_tasklet, ltb_aggr_tasklet,
+		     (unsigned long)cl);
+
+	if (classid == ltb->default_classid)
+		rcu_assign_pointer(ltb->default_cls, cl);
+	if (classid != SHADOW_CLASSID) {
+		write_lock_bh(&ltb->prio_rows_lock);
+		list_add(&cl->pnode, &ltb->prio_rows[prio]);
+		write_unlock_bh(&ltb->prio_rows_lock);
+	}
+
+	sch_tree_lock(sch);
+	qdisc_class_hash_insert(&ltb->clhash, &cl->common);
+	sch_tree_unlock(sch);
+
+	return cl;
+}
+
+static int ltb_modify_class(struct Qdisc *sch, struct ltb_class *cl,
+			    struct psched_ratecfg *ratecfg,
+			    struct psched_ratecfg *ceilcfg,
+			    u32 prio)
+{
+	struct ltb_sched *ltb = qdisc_priv(sch);
+
+	rcu_read_lock_bh();
+	cl->ratecfg = *ratecfg;
+	cl->ceilcfg = *ceilcfg;
+	cl->prio = prio;
+	cl->rate = ratecfg->rate_bytes_ps;
+	cl->ceil = ceilcfg->rate_bytes_ps;
+	cl->bw_allocated = ratecfg->rate_bytes_ps;
+	cl->high_water = cl->bw_allocated * 110 / 100;
+	cl->maxbw = BYTES_PER_INTERVAL((s64)ratecfg->rate_bytes_ps);
+
+	write_lock_bh(&ltb->prio_rows_lock);
+	list_del(&cl->pnode);
+	list_add(&cl->pnode, &ltb->prio_rows[prio]);
+	write_unlock_bh(&ltb->prio_rows_lock);
+
+	rcu_read_unlock_bh();
+
+	return 0;
+}
+
+static void ltb_destroy_class(struct Qdisc *sch, struct ltb_class *cl)
+{
+	struct ltb_sched *ltb = qdisc_priv(sch);
+	struct sk_buff *skb;
+	int i;
+
+	if (ltb->default_classid == cl->classid)
+		rcu_assign_pointer(ltb->default_cls, ltb->shadow_cls);
+	cl->state |= LTB_CLASS_CONDEMED;
+	if (cl->classid != SHADOW_CLASSID) {
+		write_lock_bh(&ltb->prio_rows_lock);
+		list_del(&cl->pnode);
+		write_unlock_bh(&ltb->prio_rows_lock);
+	}
+
+	hrtimer_cancel(&cl->aggr_timer);
+	tasklet_kill(&cl->aggr_tasklet);
+
+	/* Cleanup pending packets */
+	for (i = 0; i < cl->num_cpus; i++) {
+		while (kfifo_get(&cl->aggr_queues[i], &skb) > 0)
+			kfree_skb(skb);
+
+		while (kfifo_get(&cl->fanout_queues[i], &skb) > 0)
+			kfree_skb(skb);
+	}
+	while (kfifo_get(&cl->drain_queue, &skb) > 0)
+		kfree_skb(skb);
+
+	kfree(cl);
+}
+
+static int ltb_graft_class(struct Qdisc *sch, unsigned long arg,
+			   struct Qdisc *new, struct Qdisc **old,
+			   struct netlink_ext_ack *extack)
+{
+	struct ltb_class *cl = (struct ltb_class *)arg;
+
+	if (!new)
+		return -EINVAL;
+
+	*old = qdisc_replace(sch, new, &cl->qdisc);
+	return 0;
+}
+
+static struct Qdisc *ltb_leaf(struct Qdisc *sch, unsigned long arg)
+{
+	struct ltb_class *cl = (struct ltb_class *)arg;
+
+	return cl->qdisc;
+}
+
+static void ltb_qlen_notify(struct Qdisc *sch, unsigned long arg)
+{
+}
+
+static unsigned long ltb_find(struct Qdisc *sch, u32 handle)
+{
+	return (unsigned long)ltb_find_class(sch, handle);
+}
+
+static int ltb_change_class(struct Qdisc *sch, u32 classid,
+			    u32 parentid, struct nlattr **tca,
+			    unsigned long *arg, struct netlink_ext_ack *extack)
+{
+	struct ltb_sched *ltb  = qdisc_priv(sch);
+	struct ltb_class *cl = (struct ltb_class *)*arg, *parent;
+	struct nlattr *opt = tca[TCA_OPTIONS];
+	struct nlattr *tb[TCA_LTB_MAX + 1];
+	struct tc_ltb_opt *lopt;
+	u64 rate64, ceil64;
+	struct psched_ratecfg ratecfg, ceilcfg;
+	u32 prio;
+	int err;
+
+	if (!opt)
+		goto failure;
+
+	err = nla_parse_nested_deprecated(tb, TCA_LTB_MAX, opt, ltb_policy,
+					  NULL);
+	if (err < 0)
+		goto failure;
+
+	err = -EINVAL;
+	if (!tb[TCA_LTB_PARMS])
+		goto failure;
+
+	parent = parentid == TC_H_ROOT ? NULL : ltb_find_class(sch, parentid);
+
+	lopt = nla_data(tb[TCA_LTB_PARMS]);
+	if (!lopt->rate.rate || !lopt->ceil.rate)
+		goto failure;
+
+	rate64 = tb[TCA_LTB_RATE64] ? nla_get_u64(tb[TCA_LTB_RATE64]) : 0;
+	ceil64 = tb[TCA_LTB_CEIL64] ? nla_get_u64(tb[TCA_LTB_CEIL64]) : 0;
+	if (rate64 > ceil64)
+		goto failure;
+
+	psched_ratecfg_precompute(&ratecfg, &lopt->rate, rate64);
+	psched_ratecfg_precompute(&ceilcfg, &lopt->ceil, ceil64);
+	prio = lopt->prio;
+	if (prio >= TC_LTB_NUMPRIO)
+		prio = TC_LTB_NUMPRIO - 1;
+
+	if (!cl) {
+		if (!classid || TC_H_MAJ(classid ^ sch->handle) ||
+		    ltb_find_class(sch, classid)) {
+			err = -EINVAL;
+			goto failure;
+		}
+		cl = ltb_alloc_class(sch, parent, classid, &ratecfg, &ceilcfg,
+				     prio);
+		if (!cl) {
+			err = -ENOBUFS;
+			goto failure;
+		}
+	} else {
+		/* Modify existing class */
+		ltb_modify_class(sch, cl, &ratecfg, &ceilcfg, prio);
+	}
+	qdisc_class_hash_grow(sch, &ltb->clhash);
+	*arg = (unsigned long)cl;
+	return 0;
+
+failure:
+	return err;
+}
+
+static int ltb_delete_class(struct Qdisc *sch, unsigned long arg)
+{
+	struct ltb_sched *ltb = qdisc_priv(sch);
+	struct ltb_class *cl = (struct ltb_class *)arg;
+
+	sch_tree_lock(sch);
+	if (cl->qdisc)
+		qdisc_purge_queue(cl->qdisc);
+	qdisc_class_hash_remove(&ltb->clhash, &cl->common);
+	sch_tree_unlock(sch);
+
+	ltb_destroy_class(sch, cl);
+	return 0;
+}
+
+static void ltb_walk(struct Qdisc *sch, struct qdisc_walker *arg)
+{
+	struct ltb_sched *q = qdisc_priv(sch);
+	struct ltb_class *cl;
+	unsigned int i;
+
+	if (arg->stop)
+		return;
+
+	for (i = 0; i < q->clhash.hashsize; i++) {
+		hlist_for_each_entry(cl, &q->clhash.hash[i], common.hnode) {
+			/* We don't want to walk the shadow class */
+			if (cl->classid == SHADOW_CLASSID)
+				continue;
+
+			if (arg->count < arg->skip) {
+				arg->count++;
+				continue;
+			}
+			if (arg->fn(sch, (unsigned long)cl, arg) < 0) {
+				arg->stop = 1;
+				return;
+			}
+			arg->count++;
+		}
+	}
+}
+
+static int ltb_dump_class(struct Qdisc *sch, unsigned long arg,
+			  struct sk_buff *skb, struct tcmsg *tcm)
+{
+	struct ltb_class *cl = (struct ltb_class *)arg;
+	struct nlattr *nest;
+	struct tc_ltb_opt opt;
+
+	tcm->tcm_parent = cl->parent ? cl->parent->common.classid : TC_H_ROOT;
+	tcm->tcm_handle = cl->common.classid;
+
+	nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
+	if (!nest)
+		goto nla_put_failure;
+
+	memset(&opt, 0, sizeof(opt));
+	psched_ratecfg_getrate(&opt.rate, &cl->ratecfg);
+	psched_ratecfg_getrate(&opt.ceil, &cl->ceilcfg);
+
+	opt.measured = BPS2MBPS(cl->bw_measured);
+	opt.allocated = BPS2MBPS(cl->bw_allocated);
+	opt.high_water = BPS2MBPS(cl->high_water);
+	opt.prio = cl->prio;
+
+	if (nla_put(skb, TCA_LTB_PARMS, sizeof(opt), &opt))
+		goto nla_put_failure;
+
+	if ((cl->ratecfg.rate_bytes_ps >= (1ULL << 32)) &&
+	    nla_put_u64_64bit(skb, TCA_LTB_RATE64, cl->ratecfg.rate_bytes_ps,
+			      TCA_LTB_PAD))
+		goto nla_put_failure;
+	if ((cl->ceilcfg.rate_bytes_ps >= (1ULL << 32)) &&
+	    nla_put_u64_64bit(skb, TCA_LTB_CEIL64, cl->ceilcfg.rate_bytes_ps,
+			      TCA_LTB_PAD))
+		goto nla_put_failure;
+
+	return nla_nest_end(skb, nest);
+
+nla_put_failure:
+	nla_nest_cancel(skb, nest);
+	return -1;
+}
+
+static int ltb_dump_class_stats(struct Qdisc *sch, unsigned long arg,
+				struct gnet_dump *d)
+{
+	struct ltb_class *cl = (struct ltb_class *)arg;
+	struct gnet_stats_basic_packed bstats;
+	struct gnet_stats_queue qstats;
+	struct tc_ltb_xstats xstats;
+
+	memset(&bstats, 0, sizeof(bstats));
+	bstats.bytes = cl->stat_bytes;
+	bstats.packets = cl->stat_packets;
+	memset(&qstats, 0, sizeof(qstats));
+	qstats.drops = cl->stat_drops.counter;
+	memset(&xstats, 0, sizeof(xstats));
+	xstats.measured = BPS2MBPS(cl->bw_measured);
+	xstats.allocated = BPS2MBPS(cl->bw_allocated);
+	xstats.high_water = BPS2MBPS(cl->high_water);
+	if (gnet_stats_copy_basic(qdisc_root_sleeping_running(sch),
+				  d, NULL, &bstats) < 0 ||
+	    gnet_stats_copy_queue(d, NULL, &qstats, 0) < 0)
+		return -1;
+
+	return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
+}
+
+static struct ltb_class *ltb_classify(struct Qdisc *sch,
+				      struct ltb_sched *ltb,
+				      struct sk_buff *skb)
+{
+	struct ltb_class *cl;
+
+	/* Allow to select a class by setting skb->priority */
+	if (likely(skb->priority != 0)) {
+		cl = ltb_find_class(sch, skb->priority);
+		if (cl)
+			return cl;
+	}
+	return rcu_dereference_bh(ltb->default_cls);
+}
+
+static int ltb_enqueue(struct sk_buff *skb, struct Qdisc *sch, spinlock_t *root_lock,
+		       struct sk_buff **to_free)
+{
+	struct ltb_sched *ltb = qdisc_priv(sch);
+	struct ltb_pcpu_sched *pcpu_q;
+	struct ltb_class *cl;
+	struct ltb_pcpu_data *pcpu = this_cpu_ptr(ltb->pcpu_data);
+	int cpu;
+
+	cpu = smp_processor_id();
+	pcpu_q = qdisc_priv(pcpu->qdisc);
+	ltb_skb_cb(skb)->cpu = cpu;
+
+	cl = ltb_classify(sch, ltb, skb);
+	if (unlikely(!cl)) {
+		kfree_skb(skb);
+		return NET_XMIT_DROP;
+	}
+
+	pcpu->active = true;
+	if (unlikely(kfifo_put(&cl->aggr_queues[cpu], skb) == 0)) {
+		kfree_skb(skb);
+		atomic64_inc(&cl->stat_drops);
+		return NET_XMIT_DROP;
+	}
+
+	sch->q.qlen = 1;
+	pcpu_q->qdisc->q.qlen++;
+	tasklet_schedule(&cl->aggr_tasklet);
+	return NET_XMIT_SUCCESS;
+}
+
+static struct sk_buff *ltb_dequeue(struct Qdisc *sch)
+{
+	struct ltb_sched *ltb = qdisc_priv(sch);
+	struct ltb_pcpu_data *pcpu;
+
+	pcpu = this_cpu_ptr(ltb->pcpu_data);
+
+	if (likely(pcpu->active))
+		pcpu->active = false;
+	else
+		tasklet_schedule(&ltb->fanout_tasklet);
+
+	return NULL;
+}
+
+static void ltb_reset(struct Qdisc *sch)
+{
+	struct ltb_sched *ltb = qdisc_priv(sch);
+	struct ltb_class *cl;
+	int i;
+
+	sch->q.qlen = 0;
+	for (i = 0; i < ltb->num_cpus; i++)
+		qdisc_reset(per_cpu_ptr(ltb->pcpu_data, i)->qdisc);
+
+	for (i = 0; i < ltb->clhash.hashsize; i++) {
+		hlist_for_each_entry(cl, &ltb->clhash.hash[i], common.hnode) {
+			if (cl->qdisc)
+				qdisc_reset(cl->qdisc);
+		}
+	}
+}
+
+static void ltb_destroy(struct Qdisc *sch)
+{
+	struct ltb_sched *ltb = qdisc_priv(sch);
+	struct hlist_node *tmp;
+	struct ltb_class *cl;
+	int i;
+
+	sch->q.qlen = 0;
+	ltb->default_cls = NULL;
+	ltb->shadow_cls = NULL;
+	tasklet_kill(&ltb->fanout_tasklet);
+	if (ltb->bwbalancer_task) {
+		kthread_stop(ltb->bwbalancer_task);
+		ltb->bwbalancer_task = NULL;
+	}
+
+	for (i = 0; i < ltb->num_cpus; i++)
+		qdisc_put(per_cpu_ptr(ltb->pcpu_data, i)->qdisc);
+
+	for (i = 0; i < ltb->clhash.hashsize; i++) {
+		hlist_for_each_entry_safe(cl, tmp, &ltb->clhash.hash[i],
+					  common.hnode)
+			ltb_destroy_class(sch, cl);
+	}
+	qdisc_class_hash_destroy(&ltb->clhash);
+	free_percpu(ltb->pcpu_data);
+}
+
+static int ltb_init(struct Qdisc *sch, struct nlattr *opt,
+		    struct netlink_ext_ack *extack)
+{
+	struct ltb_sched *ltb = (struct ltb_sched *)qdisc_priv(sch);
+	struct Qdisc *q;
+	int err, i;
+	struct ltb_pcpu_sched *pcpu_q;
+	struct net_device *dev = qdisc_dev(sch);
+	u32 default_classid = 0;
+	struct psched_ratecfg ratecfg;
+
+	if (sch->parent != TC_H_ROOT)
+		return -EOPNOTSUPP;
+
+	if (opt) {
+		err = ltb_parse_opts(opt, &default_classid);
+		if (err != 0)
+			return err;
+	}
+
+	memset(ltb, 0, sizeof(*ltb));
+	rwlock_init(&ltb->prio_rows_lock);
+	for (i = 0; i < TC_LTB_NUMPRIO; i++)
+		INIT_LIST_HEAD(&ltb->prio_rows[i]);
+
+	ltb->root_qdisc = sch;
+	ltb->dev = dev;
+	ltb->num_cpus = num_online_cpus();
+	if (ltb->num_cpus > MAX_CPU_COUNT)
+		return -EOPNOTSUPP;
+
+	ltb->link_speed = get_linkspeed(ltb->dev);
+	if (ltb->link_speed <= 0)
+		pr_warn("Failed to obtain link speed\n");
+
+	err = qdisc_class_hash_init(&ltb->clhash);
+	if (err < 0)
+		return err;
+
+	ltb->pcpu_data = alloc_percpu_gfp(struct ltb_pcpu_data,
+					  GFP_KERNEL | __GFP_ZERO);
+	if (!ltb->pcpu_data) {
+		err = -ENOMEM;
+		goto error;
+	}
+
+	for (i = 0; i < ltb->num_cpus; i++) {
+		q = qdisc_create_dflt(sch->dev_queue,
+				      &ltb_pcpu_qdisc_ops, 0, NULL);
+		if (!q) {
+			err = -ENODEV;
+			goto error;
+		}
+		/* These cannot be initialized in qdisc_init() */
+		pcpu_q = (struct ltb_pcpu_sched *)qdisc_priv(q);
+		pcpu_q->cpu = i;
+		pcpu_q->ltb = ltb;
+
+		per_cpu_ptr(ltb->pcpu_data, i)->qdisc = q;
+		per_cpu_ptr(ltb->pcpu_data, i)->active = false;
+	}
+
+	ltb->default_classid = TC_H_MAKE(TC_H_MAJ(sch->handle),
+					 default_classid);
+	ratecfg.rate_bytes_ps = ltb->link_speed;
+	ltb->shadow_cls = ltb_alloc_class(sch, NULL, SHADOW_CLASSID,
+					  &ratecfg, &ratecfg, 0);
+	if (!ltb->shadow_cls) {
+		err = -EINVAL;
+		goto error;
+	}
+	ltb->default_cls = ltb->shadow_cls; /* Default hasn't been created */
+	tasklet_init(&ltb->fanout_tasklet, ltb_fanout_tasklet,
+		     (unsigned long)ltb);
+
+	/* Bandwidth balancer, this logic can be implemented in user-land. */
+	init_waitqueue_head(&ltb->bwbalancer_wq);
+	ltb->bwbalancer_task =
+	    kthread_create(ltb_bw_balancer_kthread, ltb, "ltb-balancer");
+	wake_up_process(ltb->bwbalancer_task);
+
+	sch->flags |= TCQ_F_NOLOCK;
+	return 0;
+
+error:
+	for (i = 0; i < ltb->num_cpus; i++) {
+		struct ltb_pcpu_data *pcpu = per_cpu_ptr(ltb->pcpu_data, i);
+
+		if (pcpu->qdisc) {
+			qdisc_put(pcpu->qdisc);
+			pcpu->qdisc = NULL;
+		}
+	}
+	if (ltb->pcpu_data) {
+		free_percpu(ltb->pcpu_data);
+		ltb->pcpu_data = NULL;
+	}
+	if (ltb->bwbalancer_task) {
+		kthread_stop(ltb->bwbalancer_task);
+		ltb->bwbalancer_task = NULL;
+	}
+	qdisc_class_hash_destroy(&ltb->clhash);
+	return err;
+}
+
+static int ltb_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+	struct ltb_sched *ltb  = qdisc_priv(sch);
+	struct nlattr *nest;
+	struct tc_ltb_glob gopt;
+
+	gopt.version = LTB_VERSION;
+	gopt.defcls = ltb->default_classid;
+
+	nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
+	if (!nest)
+		goto nla_put_failure;
+	if (nla_put(skb, TCA_LTB_INIT, sizeof(gopt), &gopt))
+		goto nla_put_failure;
+
+	return nla_nest_end(skb, nest);
+
+nla_put_failure:
+	nla_nest_cancel(skb, nest);
+	return -1;
+}
+
+static struct Qdisc_ops ltb_pcpu_qdisc_ops __read_mostly = {
+	.cl_ops		= NULL,
+	.id		= "ltb_percore",
+	.priv_size	= sizeof(struct ltb_sched),
+	.enqueue	= NULL,
+	.dequeue	= ltb_pcpu_dequeue,
+	.peek		= qdisc_peek_dequeued,
+	.init		= ltb_pcpu_init,
+	.dump		= NULL,
+	.owner		= THIS_MODULE,
+};
+
+static const struct Qdisc_class_ops ltb_class_ops = {
+	.graft		= ltb_graft_class,
+	.leaf		= ltb_leaf,
+	.qlen_notify	= ltb_qlen_notify,
+	.find		= ltb_find,
+	.change		= ltb_change_class,
+	.delete		= ltb_delete_class,
+	.walk		= ltb_walk,
+	.dump		= ltb_dump_class,
+	.dump_stats	= ltb_dump_class_stats,
+};
+
+static struct Qdisc_ops ltb_qdisc_ops __read_mostly = {
+	.cl_ops		= &ltb_class_ops,
+	.id		= "ltb",
+	.priv_size	= sizeof(struct ltb_sched),
+	.enqueue	= ltb_enqueue,
+	.dequeue	= ltb_dequeue,
+	.peek		= qdisc_peek_dequeued,
+	.init		= ltb_init,
+	.reset		= ltb_reset,
+	.destroy	= ltb_destroy,
+	.dump		= ltb_dump,
+	.owner		= THIS_MODULE,
+};
+
+static int __init ltb_module_init(void)
+{
+	return register_qdisc(&ltb_qdisc_ops);
+}
+
+static void __exit ltb_module_exit(void)
+{
+	unregister_qdisc(&ltb_qdisc_ops);
+}
+
+module_init(ltb_module_init)
+module_exit(ltb_module_exit)
+MODULE_LICENSE("GPL");
-- 
1.8.3.1

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