Message-ID: <1377400082.8828.100.camel@edumazet-glaptop>
Date:	Sat, 24 Aug 2013 20:08:02 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next] pkt_sched: fq: Fair Queue packet scheduler

From: Eric Dumazet <edumazet@...gle.com>

Fair Queue packet scheduler with optional per flow rate shaping.

- Uses perfect flow match (not stochastic hash like SFQ/FQ_codel)
- Uses the new_flow/old_flow separation from FQ_codel
- Special FIFO queue for high prio packets (no need for PRIO + FQ)
- Uses a hash table of RB trees to locate the flows at enqueue() time
- Smart on demand gc (at enqueue() time, RB tree lookup evicts old
  unused flows)
- Dynamic memory allocations.
- Designed to allow millions of concurrent flows per Qdisc.
- Small memory footprint : ~2K per Qdisc, and 96 bytes per flow.
- Single high resolution timer for throttled flows (if any).
- One RB tree to link throttled flows.
- Ability to have a max rate per flow. We might add a socket option
  to add per socket limitation.

Attempts have been made to add TCP pacing in TCP stack, but this
seems to add complex code to an already complex stack.

TCP pacing is welcomed for flows having idle times, as the cwnd
permits TCP stack to queue a possibly large number of packets.

This removes the 'slow start after idle' choice, hitting badly
large BDP flows.

Nicely spaced packets : here interface is 10Gbit, but flow bottleneck is
~100Mbit

cwin is big, yet FQ avoids the typical burst generated by TCP
(as in netperf TCP_RR -- -r 200000,200000)

04:29:48.340246 IP A > B: P 349144:349320(176) ack 200001 win 6431 <nop,nop,timestamp 244267845 2106896>
04:29:48.340270 IP B > A: . 200001:226065(26064) ack 349320 win 5204 <nop,nop,timestamp 2106905 244267845>
04:29:48.340830 IP B > A: . 226065:252129(26064) ack 349320 win 5204 <nop,nop,timestamp 2106905 244267845>
04:29:48.341354 IP A > B: . ack 223169 win 6431 <nop,nop,timestamp 244267853 2106905>
04:29:48.341392 IP B > A: . 252129:278193(26064) ack 349320 win 5204 <nop,nop,timestamp 2106905 244267845>
04:29:48.341891 IP B > A: . 278193:304257(26064) ack 349320 win 5204 <nop,nop,timestamp 2106905 244267845>
04:29:48.342392 IP B > A: . 304257:330321(26064) ack 349320 win 5204 <nop,nop,timestamp 2106905 244267845>
04:29:48.342892 IP B > A: . 330321:356385(26064) ack 349320 win 5204 <nop,nop,timestamp 2106905 244267845>
04:29:48.343077 IP A > B: . ack 226065 win 6431 <nop,nop,timestamp 244267854 2106905>
04:29:48.343319 IP A > B: . ack 249233 win 6431 <nop,nop,timestamp 244267855 2106905>
04:29:48.343393 IP B > A: . 356385:382449(26064) ack 349320 win 5204 <nop,nop,timestamp 2106905 244267845>
04:29:48.343808 IP B > A: . 382449:399825(17376) ack 349320 win 5204 <nop,nop,timestamp 2106906 244267853>
04:29:48.344085 IP B > A: P 399825:400001(176) ack 349320 win 5204 <nop,nop,timestamp 2106906 244267853>
04:29:48.345174 IP A > B: . ack 252129 win 6431 <nop,nop,timestamp 244267856 2106905>
04:29:48.345414 IP A > B: . ack 275297 win 6431 <nop,nop,timestamp 244267857 2106905>
04:29:48.347268 IP A > B: . ack 278193 win 6431 <nop,nop,timestamp 244267859 2106905>
04:29:48.347507 IP A > B: . ack 301361 win 6431 <nop,nop,timestamp 244267859 2106905>

TCP timestamps show that most packets were queued in the same ms
timeframe (TSval 2106905), but FQ managed to send them right
in time to avoid a big burst, and fill the pipe.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/uapi/linux/pkt_sched.h |   34 +
 net/sched/Kconfig              |   14 
 net/sched/Makefile             |    1 
 net/sched/sch_fq.c             |  771 +++++++++++++++++++++++++++++++
 4 files changed, 820 insertions(+)

diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 09d62b92..ed434c5 100644
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h
@@ -744,4 +744,38 @@ struct tc_fq_codel_xstats {
 	};
 };
 
+/* FQ */
+
+enum {
+	TCA_FQ_UNSPEC,
+
+	TCA_FQ_PLIMIT,		/* limit of total number of packets in queue */
+
+	TCA_FQ_FLOW_PLIMIT,	/* limit of packets per flow */
+
+	TCA_FQ_QUANTUM,		/* RR quantum */
+
+	TCA_FQ_RATE_ENABLE,	/* enable/disable rate limiting */
+
+	TCA_FQ_FLOW_DEFAULT_RATE,/* for sockets with unspecified sk_rate,
+				  * use the following rate
+				  */
+
+	TCA_FQ_FLOW_MAX_RATE,	/* per flow max rate */
+
+	TCA_FQ_BUCKETS_LOG,	/* log2(number of buckets) */
+	__TCA_FQ_MAX
+};
+
+#define TCA_FQ_MAX	(__TCA_FQ_MAX - 1)
+
+struct tc_fq_qd_stats {
+	__u64	gc_flows;
+	__u64	highprio_packets;
+	__u64	tcp_retrans;
+	__u64	throttled;
+	__u64	flows_plimit;
+	__u64	pkts_too_long;
+	__u64	allocation_errors;
+};
 #endif
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index 235e01a..c03a32a 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -272,6 +272,20 @@ config NET_SCH_FQ_CODEL
 
 	  If unsure, say N.
 
+config NET_SCH_FQ
+	tristate "Fair Queue"
+	help
+	  Say Y here if you want to use the FQ packet scheduling algorithm.
+
+	  FQ does flow separation, and is able to respect pacing requirements
+	  set by TCP stack into sk->sk_pacing_rate (for localy generated
+	  traffic)
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called sch_fq.
+
+	  If unsure, say N.
+
 config NET_SCH_INGRESS
 	tristate "Ingress Qdisc"
 	depends on NET_CLS_ACT
diff --git a/net/sched/Makefile b/net/sched/Makefile
index 978cbf0..e5f9abe 100644
--- a/net/sched/Makefile
+++ b/net/sched/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_NET_SCH_CHOKE)	+= sch_choke.o
 obj-$(CONFIG_NET_SCH_QFQ)	+= sch_qfq.o
 obj-$(CONFIG_NET_SCH_CODEL)	+= sch_codel.o
 obj-$(CONFIG_NET_SCH_FQ_CODEL)	+= sch_fq_codel.o
+obj-$(CONFIG_NET_SCH_FQ)	+= sch_fq.o
 
 obj-$(CONFIG_NET_CLS_U32)	+= cls_u32.o
 obj-$(CONFIG_NET_CLS_ROUTE4)	+= cls_route.o
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
new file mode 100644
index 0000000..87a054d
--- /dev/null
+++ b/net/sched/sch_fq.c
@@ -0,0 +1,771 @@
+/*
+ * net/sched/sch_fq.c Fair Queue Packet Scheduler (per flow pacing)
+ *
+ *  Copyright (C) 2013 Eric Dumazet <edumazet@...gle.com>
+ *
+ *	This program is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU General Public License
+ *	as published by the Free Software Foundation; either version
+ *	2 of the License, or (at your option) any later version.
+ *
+ *  Meant to be used for localy generated traffic :
+ *  Fast classification depends on skb->sk being set before reaching us.
+ *  If not, (router workload), we use rxhash as fallback, with 32 bits wide hash.
+ *  All packets belonging to a socket are considered as a 'flow'.
+ *
+ *  Flows are dynamically allocated and stored in a hash table of RB trees
+ *  They are also part of one Round Robin 'queues' (new or old flows)
+ *
+ *  Burst avoidance (aka pacing) capability :
+ *  Transport (eg TCP) can set in sk->sk_pacing_rate a rate, enqueue a
+ *  bunch of packets, and this packet scheduler adds delay between
+ *  packets to respect rate limitation.
+ *
+ *  enqueue() :
+ *   - lookup one RB tree (out of 256 or more) to find the flow.
+ *     If non existent flow, create it, add it to the tree.
+ *     Add skb to the per flow list of skb (fifo).
+ *   - Use a special fifo for high prio packets
+ *
+ *  dequeue() : serves flows in Round Robin
+ *  Note : When a flow becomes empty, we do not immediately remove it from
+ *  rb trees, for performance reasons (its expected to send additional packets,
+ *  or SLAB cache will reuse socket for another flow)
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/jiffies.h>
+#include <linux/string.h>
+#include <linux/in.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <linux/rbtree.h>
+#include <linux/hash.h>
+#include <net/netlink.h>
+#include <net/pkt_sched.h>
+#include <net/sock.h>
+#include <net/tcp_states.h>
+
+/*
+ * Per flow structure, dynamically allocated
+ */
+struct fq_flow {
+	struct sk_buff	*head; /* list of skbs for this flow : first skb */
+	union {
+		struct sk_buff *tail;	/* last skb in the list */
+		unsigned long  age;	/* jiffies when flow was emptied, for gc */
+	};
+	struct rb_node	fq_node; /* anchor in fq_root[] trees */
+	struct sock	*sk;
+	int		qlen;	/* number of packets in flow queue */
+	int		deficit;
+	struct fq_flow *next;	/* next pointer in RR lists, or &detached */
+
+	struct rb_node  rate_node; /* anchor in q->delayed tree */
+	u64		time_next_packet;
+};
+
+struct fq_flow_head {
+	struct fq_flow *first;
+	struct fq_flow *last;
+};
+
+struct fq_sched_data {
+	struct fq_flow_head new_flows;
+
+	struct fq_flow_head old_flows;
+
+	struct rb_root	delayed; /* for rate limited flows */
+	u64		time_next_delayed_flow;
+
+	struct fq_flow	internal;	/* for non classified or high prio packets */
+	u32		quantum;
+	u32		flow_default_rate;/* rate per flow : bytes per second */
+	u32		flow_max_rate;	/* optional max rate per flow */
+	u32		flow_plimit;	/* max packets per flow */
+	struct rb_root	*fq_root;
+	u8		rate_enable;
+	u8		fq_trees_log;
+
+	u32		flows;
+	u32		inactive_flows;
+	u32		throttled_flows;
+
+	u64		stat_gc_flows;
+	u64		stat_internal_packets;
+	u64		stat_tcp_retrans;
+	u64		stat_throttled;
+	u64		stat_flows_plimit;
+	u64		stat_pkts_too_long;
+	u64		stat_allocation_errors;
+	struct qdisc_watchdog watchdog;
+};
+
+/* special value to mark a detached flow (not on old/new list) */
+static struct fq_flow detached, throttled;
+
+static void fq_flow_set_detached(struct fq_flow *f)
+{
+	f->next = &detached;
+}
+
+static bool fq_flow_is_detached(const struct fq_flow *f)
+{
+	return f->next == &detached;
+}
+
+static void fq_flow_set_throttled(struct fq_sched_data *q, struct fq_flow *f)
+{
+	struct rb_node **p = &q->delayed.rb_node, *parent = NULL;
+
+	while (*p) {
+		struct fq_flow *aux;
+
+		parent = *p;
+		aux = container_of(parent, struct fq_flow, rate_node);
+		if (f->time_next_packet >= aux->time_next_packet)
+			p = &parent->rb_right;
+		else
+			p = &parent->rb_left;
+	}
+	rb_link_node(&f->rate_node, parent, p);
+	rb_insert_color(&f->rate_node, &q->delayed);
+	q->throttled_flows++;
+	q->stat_throttled++;
+
+	f->next = &throttled;
+	if (q->time_next_delayed_flow > f->time_next_packet)
+		q->time_next_delayed_flow = f->time_next_packet;
+}
+
+
+static struct kmem_cache *fq_flow_cachep __read_mostly;
+
+static void fq_flow_add_tail(struct fq_flow_head *head, struct fq_flow *flow)
+{
+	if (head->first)
+		head->last->next = flow;
+	else
+		head->first = flow;
+	head->last = flow;
+	flow->next = NULL;
+}
+
+/* limit number of collected flows per round */
+#define FQ_GC_MAX 8
+#define FQ_GC_AGE (3*HZ)
+
+static bool fq_gc_candidate(const struct fq_flow *f)
+{
+	return fq_flow_is_detached(f) &&
+	       time_after(jiffies, f->age + FQ_GC_AGE);
+}
+
+static void fq_gc(struct fq_sched_data *q,
+		  struct rb_root *root,
+		  struct sock *sk)
+{
+	struct fq_flow *f, *tofree[FQ_GC_MAX];
+	struct rb_node **p, *parent;
+	int fcnt = 0;
+
+	p = &root->rb_node;
+	parent = NULL;
+	while (*p) {
+		parent = *p;
+
+		f = container_of(parent, struct fq_flow, fq_node);
+		if (f->sk == sk)
+			break;
+
+		if (fq_gc_candidate(f)) {
+			tofree[fcnt++] = f;
+			if (fcnt == FQ_GC_MAX)
+				break;
+		}
+
+		if (f->sk > sk)
+			p = &parent->rb_right;
+		else
+			p = &parent->rb_left;
+	}
+
+	q->flows -= fcnt;
+	q->inactive_flows -= fcnt;
+	q->stat_gc_flows += fcnt;
+	while (fcnt) {
+		struct fq_flow *f = tofree[--fcnt];
+
+		rb_erase(&f->fq_node, root);
+		kmem_cache_free(fq_flow_cachep, f);
+	}
+}
+
+static const u8 prio2band[TC_PRIO_MAX + 1] = {
+	1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1
+};
+
+static struct fq_flow *fq_classify(struct sk_buff *skb, struct fq_sched_data *q)
+{
+	struct rb_node **p, *parent;
+	struct sock *sk = skb->sk;
+	struct rb_root *root;
+	struct fq_flow *f;
+	int band;
+
+	/* warning: no starvation prevention... */
+	band = prio2band[skb->priority & TC_PRIO_MAX];
+	if (unlikely(band == 0))
+		return &q->internal;
+
+	if (unlikely(!sk)) {
+		/* By forcing low order bit to 1, we make sure to not
+		 * collide with a local flow (socket pointers are word aligned)
+		 */
+		sk = (struct sock *)(skb_get_rxhash(skb) | 1L);
+	}
+
+	root = &q->fq_root[hash_32((u32)(long)sk, q->fq_trees_log)];
+
+	if (q->flows >= (2U << q->fq_trees_log) &&
+	    q->inactive_flows > q->flows/2)
+		fq_gc(q, root, sk);
+
+	p = &root->rb_node;
+	parent = NULL;
+	while (*p) {
+		parent = *p;
+
+		f = container_of(parent, struct fq_flow, fq_node);
+		if (f->sk == sk)
+			return f;
+
+		if (f->sk > sk)
+			p = &parent->rb_right;
+		else
+			p = &parent->rb_left;
+	}
+
+	f = kmem_cache_zalloc(fq_flow_cachep, GFP_ATOMIC | __GFP_NOWARN);
+	if (unlikely(!f)) {
+		q->stat_allocation_errors++;
+		return &q->internal;
+	}
+	fq_flow_set_detached(f);
+	f->sk = sk;
+
+	rb_link_node(&f->fq_node, parent, p);
+	rb_insert_color(&f->fq_node, root);
+
+	q->flows++;
+	q->inactive_flows++;
+	return f;
+}
+
+
+/* remove one skb from head of flow queue */
+static struct sk_buff *fq_dequeue_head(struct fq_flow *flow)
+{
+	struct sk_buff *skb = flow->head;
+
+	if (skb) {
+		flow->head = skb->next;
+		skb->next = NULL;
+		flow->qlen--;
+	}
+	return skb;
+}
+
+/* We might add in the future detection of retransmits
+ * For the time being, just return false
+ */
+static bool skb_is_retransmit(struct sk_buff *skb)
+{
+	return false;
+}
+
+/* add skb to flow queue
+ * flow queue is a linked list, kind of FIFO, except for TCP retransmits
+ * We special case tcp retransmits to be transmitted before other packets.
+ * We rely on fact that TCP retransmits are unlikely, so we do not waste
+ * a separate queue or a pointer.
+ * head->  [retrans pkt 1]
+ *         [retrans pkt 2]
+ *         [ normal pkt 1]
+ *         [ normal pkt 2]
+ *         [ normal pkt 3]
+ * tail->  [ normal pkt 4]
+ */
+static void flow_queue_add(struct fq_flow *flow, struct sk_buff *skb)
+{
+	struct sk_buff *prev, *head = flow->head;
+
+	skb->next = NULL;
+	if (!head) {
+		flow->head = skb;
+		flow->tail = skb;
+		return;
+	}
+	if (likely(!skb_is_retransmit(skb))) {
+		flow->tail->next = skb;
+		flow->tail = skb;
+		return;
+	}
+
+	/* This skb is a tcp retransmit,
+	 * find the last retrans packet in the queue
+	 */
+	prev = NULL;
+	while (skb_is_retransmit(head)) {
+		prev = head;
+		head = head->next;
+		if (!head)
+			break;
+	}
+	if (!prev) { /* no rtx packet in queue, become the new head */
+		skb->next = flow->head;
+		flow->head = skb;
+	} else {
+		if (prev == flow->tail)
+			flow->tail = skb;
+		else
+			skb->next = prev->next;
+		prev->next = skb;
+	}
+}
+
+static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+{
+	struct fq_sched_data *q = qdisc_priv(sch);
+	struct fq_flow *f;
+
+	if (sch->q.qlen >= sch->limit)
+		return qdisc_drop(skb, sch);
+
+	f = fq_classify(skb, q);
+	if (f->qlen >= q->flow_plimit && f != &q->internal) {
+		q->stat_flows_plimit++;
+		return qdisc_drop(skb, sch);
+	}
+
+	f->qlen++;
+	flow_queue_add(f, skb);
+	if (skb_is_retransmit(skb))
+		q->stat_tcp_retrans++;
+	sch->qstats.backlog += qdisc_pkt_len(skb);
+	if (fq_flow_is_detached(f)) {
+		fq_flow_add_tail(&q->new_flows, f);
+		f->deficit = q->quantum;
+		q->inactive_flows--;
+		qdisc_unthrottled(sch);
+	}
+	if (f == &q->internal) {
+		q->stat_internal_packets++;
+		qdisc_unthrottled(sch);
+	}
+	sch->q.qlen++;
+
+	return NET_XMIT_SUCCESS;
+}
+
+static void fq_check_throttled(struct fq_sched_data *q, u64 now)
+{
+	struct rb_node *p;
+
+	if (q->time_next_delayed_flow > now)
+		return;
+
+	q->time_next_delayed_flow = ~0ULL;
+	while ((p = rb_first(&q->delayed)) != NULL) {
+		struct fq_flow *f = container_of(p, struct fq_flow, rate_node);
+		if (f->time_next_packet > now) {
+			q->time_next_delayed_flow = f->time_next_packet;
+			break;
+		}
+		rb_erase(p, &q->delayed);
+		q->throttled_flows--;
+		fq_flow_add_tail(&q->old_flows, f);
+	}
+}
+
+static struct sk_buff *fq_dequeue(struct Qdisc *sch)
+{
+	struct fq_sched_data *q = qdisc_priv(sch);
+	u64 now = ktime_to_ns(ktime_get());
+	struct fq_flow_head *head;
+	struct sk_buff *skb;
+	struct fq_flow *f;
+
+	skb = fq_dequeue_head(&q->internal);
+	if (skb)
+		goto out;
+	fq_check_throttled(q, now);
+begin:
+	head = &q->new_flows;
+	if (!head->first) {
+		head = &q->old_flows;
+		if (!head->first) {
+			if (q->time_next_delayed_flow != ~0ULL)
+				qdisc_watchdog_schedule_ns(&q->watchdog,
+							   q->time_next_delayed_flow);
+			return NULL;
+		}
+	}
+	f = head->first;
+
+	if (f->deficit <= 0) {
+		f->deficit += q->quantum;
+		head->first = f->next;
+		fq_flow_add_tail(&q->old_flows, f);
+		goto begin;
+	}
+
+	if (f->head && now < f->time_next_packet) {
+		head->first = f->next;
+		fq_flow_set_throttled(q, f);
+		goto begin;
+	}
+
+	skb = fq_dequeue_head(f);
+	if (!skb) {
+		head->first = f->next;
+		/* force a pass through old_flows to prevent starvation */
+		if ((head == &q->new_flows) && q->old_flows.first) {
+			fq_flow_add_tail(&q->old_flows, f);
+		} else {
+			fq_flow_set_detached(f);
+			f->age = jiffies;
+			q->inactive_flows++;
+		}
+		goto begin;
+	}
+	f->deficit -= qdisc_pkt_len(skb);
+	f->time_next_packet = now;
+
+	/* TOCHECK : The TCP_TIME_WAIT test might be not needed,
+	 * egress/ingress
+	 */
+
+	if (q->rate_enable && skb->sk && skb->sk->sk_state != TCP_TIME_WAIT) {
+		u32 rate = skb->sk->sk_pacing_rate ?: q->flow_default_rate;
+	
+		rate = min(rate, q->flow_max_rate);
+		if (rate) {
+			u64 len = (u64)qdisc_pkt_len(skb) * NSEC_PER_SEC;
+
+			do_div(len, rate);
+
+			/* Since socket rate can change later,
+			 * clamp the delay to 125 ms.
+			 * TODO: maybe segment the too big skb, as in commit
+			 * e43ac79a4bc ("sch_tbf: segment too big GSO packets")
+			 */
+			if (unlikely(len > 125 * NSEC_PER_MSEC)) {
+				len = 125 * NSEC_PER_MSEC;
+				q->stat_pkts_too_long++;
+			}
+
+			f->time_next_packet = now + len;
+		}
+	}
+out:
+	prefetch(&skb->end);
+	sch->qstats.backlog -= qdisc_pkt_len(skb);
+	qdisc_bstats_update(sch, skb);
+	sch->q.qlen--;
+	qdisc_unthrottled(sch);
+	return skb;
+}
+
+static void fq_reset(struct Qdisc *sch)
+{
+	struct sk_buff *skb;
+
+	while ((skb = fq_dequeue(sch)) != NULL)
+		kfree_skb(skb);
+}
+
+static void fq_rehash(struct fq_sched_data *q,
+		      struct rb_root *old_array, u32 old_log,
+		      struct rb_root *new_array, u32 new_log)
+{
+	struct rb_node *op, **np, *parent;
+	struct rb_root *oroot, *nroot;
+	struct fq_flow *of, *nf;
+	int fcnt = 0;
+	u32 idx;
+
+	for (idx = 0; idx < (1U << old_log); idx++) {
+		oroot = &old_array[idx];
+		while ((op = rb_first(oroot)) != NULL) {
+			rb_erase(op, oroot);
+			of = container_of(op, struct fq_flow, fq_node);
+			if (fq_gc_candidate(of)) {
+				fcnt++;
+				kmem_cache_free(fq_flow_cachep, of);
+				continue;
+			}
+			nroot = &new_array[hash_32((u32)(long)of->sk, new_log)];
+			
+			np = &nroot->rb_node;
+			parent = NULL;
+			while (*np) {
+				parent = *np;
+
+				nf = container_of(parent, struct fq_flow, fq_node);
+				BUG_ON(nf->sk == of->sk);
+
+				if (nf->sk > of->sk)
+					np = &parent->rb_right;
+				else
+					np = &parent->rb_left;
+			}
+
+			rb_link_node(&of->fq_node, parent, np);
+			rb_insert_color(&of->fq_node, nroot);
+		}
+	}
+	q->flows -= fcnt;
+	q->inactive_flows -= fcnt;
+	q->stat_gc_flows += fcnt;
+}
+
+static int fq_resize(struct fq_sched_data *q, u32 log)
+{
+	struct rb_root *array;
+	u32 idx;
+
+	if (q->fq_root && log == q->fq_trees_log)
+		return 0;
+
+	array = kmalloc(sizeof(struct rb_root) << log, GFP_KERNEL);
+	if (!array)
+		return -ENOMEM;
+
+	for (idx = 0; idx < (1U << log); idx++)
+		array[idx] = RB_ROOT;
+
+	if (q->fq_root) {
+		fq_rehash(q, q->fq_root, q->fq_trees_log, array, log);
+		kfree(q->fq_root);
+	}
+	q->fq_root = array;
+	q->fq_trees_log = log;
+
+	return 0;
+}
+
+static const struct nla_policy fq_policy[TCA_FQ_MAX + 1] = {
+	[TCA_FQ_PLIMIT]			= { .type = NLA_U32 },
+	[TCA_FQ_FLOW_PLIMIT]		= { .type = NLA_U32 },
+	[TCA_FQ_QUANTUM]		= { .type = NLA_U32 },
+	[TCA_FQ_RATE_ENABLE]		= { .type = NLA_U32 },
+	[TCA_FQ_FLOW_DEFAULT_RATE]	= { .type = NLA_U32 },
+	[TCA_FQ_FLOW_MAX_RATE]		= { .type = NLA_U32 },
+	[TCA_FQ_BUCKETS_LOG]		= { .type = NLA_U32 },
+};
+
+static int fq_change(struct Qdisc *sch, struct nlattr *opt)
+{
+	struct fq_sched_data *q = qdisc_priv(sch);
+	struct nlattr *tb[TCA_FQ_MAX + 1];
+	int err, drop_count = 0;
+	u32 fq_log;
+
+	if (!opt)
+		return -EINVAL;
+
+	err = nla_parse_nested(tb, TCA_FQ_MAX, opt, fq_policy);
+	if (err < 0)
+		return err;
+
+	sch_tree_lock(sch);
+
+	fq_log = q->fq_trees_log;
+
+	if (tb[TCA_FQ_BUCKETS_LOG]) {
+		u32 nval = nla_get_u32(tb[TCA_FQ_BUCKETS_LOG]);
+
+		if (nval >= 1 && nval <= ilog2(256*1024))
+			fq_log = nval;
+		else
+			err = -EINVAL;
+	}
+	if (tb[TCA_FQ_PLIMIT])
+		sch->limit = nla_get_u32(tb[TCA_FQ_PLIMIT]);
+
+	if (tb[TCA_FQ_FLOW_PLIMIT])
+		q->flow_plimit = nla_get_u32(tb[TCA_FQ_FLOW_PLIMIT]);
+
+	if (tb[TCA_FQ_QUANTUM])
+		q->quantum = nla_get_u32(tb[TCA_FQ_QUANTUM]);
+
+	if (tb[TCA_FQ_FLOW_DEFAULT_RATE])
+		q->flow_default_rate = nla_get_u32(tb[TCA_FQ_FLOW_DEFAULT_RATE]);
+
+	if (tb[TCA_FQ_FLOW_MAX_RATE])
+		q->flow_max_rate = nla_get_u32(tb[TCA_FQ_FLOW_MAX_RATE]);
+
+	if (tb[TCA_FQ_RATE_ENABLE]) {
+		u32 enable = nla_get_u32(tb[TCA_FQ_RATE_ENABLE]);
+
+		if (enable <= 1)
+			q->rate_enable = enable;
+		else
+			err = -EINVAL;
+	}
+
+	if (!err)
+		err = fq_resize(q, fq_log);
+
+	while (sch->q.qlen > sch->limit) {
+		struct sk_buff *skb = fq_dequeue(sch);
+
+		kfree_skb(skb);
+		drop_count++;
+	}
+	qdisc_tree_decrease_qlen(sch, drop_count);
+
+	sch_tree_unlock(sch);
+	return err;
+}
+
+static void fq_destroy(struct Qdisc *sch)
+{
+	struct fq_sched_data *q = qdisc_priv(sch);
+	struct rb_root *root;
+	struct rb_node *p;
+	unsigned int idx;
+
+	if (q->fq_root) {
+		for (idx = 0; idx < (1U << q->fq_trees_log); idx++) {
+			root = &q->fq_root[idx];
+			while ((p = rb_first(root)) != NULL) {
+				rb_erase(p, root);
+				kmem_cache_free(fq_flow_cachep,
+						container_of(p, struct fq_flow, fq_node));
+			}	
+		}
+		kfree(q->fq_root);
+	}
+	qdisc_watchdog_cancel(&q->watchdog);	
+}
+
+static int fq_init(struct Qdisc *sch, struct nlattr *opt)
+{
+	struct fq_sched_data *q = qdisc_priv(sch);
+	int err;
+
+	sch->limit = 10000;
+	q->flow_plimit = 100;
+	q->quantum = 2 * psched_mtu(qdisc_dev(sch));
+	q->flow_default_rate = 0;
+	q->flow_max_rate = ~0U;
+	q->rate_enable = 1;
+	q->new_flows.first = NULL;
+	q->old_flows.first = NULL;
+	q->delayed = RB_ROOT;
+	q->fq_root = NULL;
+	q->fq_trees_log = ilog2(256);
+	qdisc_watchdog_init(&q->watchdog, sch);
+
+	if (opt)
+		err = fq_change(sch, opt);
+	else
+		err = fq_resize(q, q->fq_trees_log);
+
+	return err;
+}
+
+static int fq_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+	struct fq_sched_data *q = qdisc_priv(sch);
+	struct nlattr *opts;
+
+	opts = nla_nest_start(skb, TCA_OPTIONS);
+	if (opts == NULL)
+		goto nla_put_failure;
+
+	if (nla_put_u32(skb, TCA_FQ_PLIMIT, sch->limit) ||
+	    nla_put_u32(skb, TCA_FQ_FLOW_PLIMIT, q->flow_plimit) ||
+	    nla_put_u32(skb, TCA_FQ_QUANTUM, q->quantum) ||
+	    nla_put_u32(skb, TCA_FQ_RATE_ENABLE, q->rate_enable) ||
+	    nla_put_u32(skb, TCA_FQ_FLOW_DEFAULT_RATE, q->flow_default_rate) ||
+	    nla_put_u32(skb, TCA_FQ_FLOW_MAX_RATE, q->flow_max_rate) ||
+	    nla_put_u32(skb, TCA_FQ_BUCKETS_LOG, q->fq_trees_log))
+		goto nla_put_failure;
+
+	nla_nest_end(skb, opts);
+	return skb->len;
+
+nla_put_failure:
+	return -1;
+}
+
+static int fq_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
+{
+	struct fq_sched_data *q = qdisc_priv(sch);
+	struct tc_fq_qd_stats st = {
+		.gc_flows		= q->stat_gc_flows,
+		.highprio_packets	= q->stat_internal_packets,
+		.tcp_retrans		= q->stat_tcp_retrans,
+		.throttled		= q->stat_throttled,
+		.flows_plimit		= q->stat_flows_plimit,
+		.pkts_too_long		= q->stat_pkts_too_long,
+		.allocation_errors	= q->stat_allocation_errors,
+	};
+		
+	pr_debug("fq_dump_stats tcp_retrans %llu flows %u inactive %u gc %llu throttled %u/%llu internal %llu\n",
+		 q->stat_tcp_retrans, q->flows, q->inactive_flows,
+		 q->stat_gc_flows, q->throttled_flows, q->stat_throttled,
+		 q->stat_internal_packets);
+
+	return gnet_stats_copy_app(d, &st, sizeof(st));
+}
+
+static struct Qdisc_ops fq_qdisc_ops __read_mostly = {
+	.id		=	"fq",
+	.priv_size	=	sizeof(struct fq_sched_data),
+
+	.enqueue	=	fq_enqueue,
+	.dequeue	=	fq_dequeue,
+	.peek		=	qdisc_peek_dequeued,
+	.init		=	fq_init,
+	.reset		=	fq_reset,
+	.destroy	=	fq_destroy,
+	.change		=	fq_change,
+	.dump		=	fq_dump,
+	.dump_stats	=	fq_dump_stats,
+	.owner		=	THIS_MODULE,
+};
+
+static int __init fq_module_init(void)
+{
+	int ret;
+
+	fq_flow_cachep = kmem_cache_create("fq_flow_cache",
+					   sizeof(struct fq_flow),
+					   0, 0, NULL);
+	if (!fq_flow_cachep)
+		return -ENOMEM;
+
+	ret = register_qdisc(&fq_qdisc_ops);
+	if (ret)
+		kmem_cache_destroy(fq_flow_cachep);
+	return ret;
+}
+
+static void __exit fq_module_exit(void)
+{
+	unregister_qdisc(&fq_qdisc_ops);
+	kmem_cache_destroy(fq_flow_cachep);
+}
+
+module_init(fq_module_init)
+module_exit(fq_module_exit)
+MODULE_AUTHOR("Eric Dumazet");
+MODULE_LICENSE("GPL");


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