patch-2.1.68 linux/net/sched/sch_csz.c

• Lines: 833
• Date: Sun Nov 30 14:00:40 1997
• Orig file: v2.1.67/linux/net/sched/sch_csz.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.1.67/linux/net/sched/sch_csz.c linux/net/sched/sch_csz.c
@@ -0,0 +1,832 @@
+/*
+ * net/sched/sch_csz.c	Clark-Shenker-Zhang scheduler.
+ *
+ *		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.
+ *
+ * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
+ *
+ */
+
+#include <asm/uaccess.h>
+#include <asm/system.h>
+#include <asm/bitops.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <linux/in.h>
+#include <linux/errno.h>
+#include <linux/interrupt.h>
+#include <linux/if_ether.h>
+#include <linux/inet.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/notifier.h>
+#include <net/ip.h>
+#include <net/route.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <net/pkt_sched.h>
+
+
+/*	Clark-Shenker-Zhang algorithm.
+	=======================================
+
+	SOURCE.
+
+	David D. Clark, Scott Shenker and Lixia Zhang
+	"Supporting Real-Time Applications in an Integrated Services Packet
+	Network: Architecture and Mechanism".
+
+	CBQ presents a flexible universal algorithm for packet scheduling,
+	but it has pretty poor delay characteristics.
+	Round-robin scheduling and link-sharing goals
+	apparently contradict to minimization of network delay and jitter.
+	Moreover, correct handling of predicted flows seems to be
+	impossible in CBQ.
+
+	CSZ presents more precise but less flexible and less efficient
+	approach. As I understand, the main idea is to create
+	WFQ flows for each guaranteed service and to allocate
+	the rest of bandwith to dummy flow-0. Flow-0 comprises
+	the predicted services and the best effort traffic;
+	it is handled by a priority scheduler with the highest
+	priority band allocated	for predicted services, and the rest ---
+	to the best effort packets.
+
+	Note, that in CSZ flows are NOT limited to their bandwidth.
+	It is supposed, that flow passed admission control at the edge
+	of QoS network and it more need no shaping. Any attempt to improve
+	the flow or to shape it to a token bucket at intermediate hops
+	will introduce undesired delays and raise jitter.
+
+	At the moment CSZ is the only scheduler that provides
+	real guaranteed service. Another schemes (including CBQ)
+	do not provide guaranteed delay and randomize jitter.
+	There exists the statement (Sally Floyd), that delay
+	can be estimated by a IntServ compliant formulae.
+	This result is true formally, but it is wrong in principle.
+	At first, it ignores delays introduced by link sharing.
+	And the second (and main) it limits bandwidth,
+	it is fatal flaw.
+
+        ALGORITHM.
+
+	--- Notations.
+
+	$B$ is link bandwidth (bits/sec).
+
+	$I$ is set of all flows, including flow $0$.
+	Every flow $a \in I$ has associated bandwidth slice $r_a < 1$ and
+	$\sum_{a \in I} r_a = 1$.
+
+	--- Flow model.
+
+	Let $m_a$ is number of backlogged bits in flow $a$.
+	The flow is {\em active }, if $m_a > 0$.
+	This number is discontinuous function of time;
+	when a packet $i$ arrives:
+	\[
+	m_a(t_i+0) - m_a(t_i-0) = L^i,
+	\]
+	where $L^i$ is the length of arrived packet.
+	The flow queue is drained continuously until $m_a == 0$:
+	\[
+	{d m_a \over dt} = - { B r_a \over \sum_{b \in A} r_b}.
+	\]
+	I.e. flow rates are their allocated rates proportionally
+	scaled to take all available link bandwidth. Apparently,
+	it is not the only possible policy. F.e. CBQ classes
+	without borrowing would be modelled by:
+	\[
+	{d m_a \over dt} = - B r_a .
+	\]
+	More complicated hierarchical bandwidth allocation
+	policies are possible, but, unfortunately, basic
+	flows equation have simple solution only for proportional
+	scaling.
+
+	--- Departure times.
+
+	We calculate time until the last bit of packet will be sent:
+	\[
+	E_a^i(t) = { m_a(t_i) - \delta_a(t) \over r_a },
+	\]
+	where $\delta_a(t)$ is number of bits drained since $t_i$.
+	We have to evaluate $E_a^i$ for all queued packets,
+	then find packet with minimal $E_a^i$ and send it.
+
+	It sounds good, but direct implementation of the algorithm
+	is absolutely infeasible. Luckily, if flow rates
+	are scaled proportionally, the equations have simple solution.
+	
+	The differential equation for $E_a^i$ is
+	\[
+	{d E_a^i (t) \over dt } = - { d \delta_a(t) \over dt} { 1 \over r_a} =
+	{ B \over \sum_{b \in A} r_b}
+	\]
+	with initial condition
+	\[
+	E_a^i (t_i) = { m_a(t_i) \over r_a } .
+	\]
+
+	Let's introduce an auxiliary function $R(t)$:
+
+	--- Round number.
+
+	Consider the following model: we rotate over active flows,
+	sending $r_a B$ bits from every flow, so that we send
+	$B \sum_{a \in A} r_a$ bits per round, that takes
+	$\sum_{a \in A} r_a$ seconds.
+	
+	Hence, $R(t)$ (round number) is monotonically increasing
+	linear function	of time when $A$ is not changed
+	\[
+	{ d R(t) \over dt } = { 1 \over \sum_{a \in A} r_a }
+	\]
+	and it is continuous when $A$ changes.
+
+	The central observation is that the quantity
+	$F_a^i = R(t) + E_a^i(t)/B$ does not depend on time at all!
+	$R(t)$ does not depend on flow, so that $F_a^i$ can be
+	calculated only once on packet arrival, and we need not
+	recalculation of $E$ numbers and resorting queues.
+	Number $F_a^i$ is called finish number of the packet.
+	It is just value of $R(t)$, when the last bit of packet
+	will be sent out.
+
+	Maximal finish number on flow is called finish number of flow
+	and minimal one is "start number of flow".
+	Apparently, flow is active if and only if $F_a \leq R$.
+
+	When packet of length $L_i$ bit arrives to flow $a$ at time $t_i$,
+	we calculate number $F_a^i$ as:
+
+	If flow was inactive ($F_a < R$):
+	$F_a^i = R(t) + {L_i \over B r_a}$
+	otherwise
+	$F_a^i = F_a + {L_i \over B r_a}$
+
+	These equations complete the algorithm specification.
+
+	It looks pretty hairy, but there exists a simple
+	procedure for solving these equations.
+	See procedure csz_update(), that is a generalization of
+	algorithm from S. Keshav's thesis Chapter 3
+	"Efficient Implementation of Fair Queeing".
+
+	NOTES.
+
+	* We implement only the simplest variant of CSZ,
+	when flow-0 is explicit 4band priority fifo.
+	It is bad, but we need "peek" operation in addition
+	to "dequeue" to implement complete CSZ.
+	I do not want to make it, until it is not absolutely
+	necessary.
+	
+	* A primitive support for token bucket filtering
+	presents too. It directly contradicts to CSZ, but
+	though the Internet is on the globe ... :-)
+	yet "the edges of the network" really exist.
+	
+	BUGS.
+
+	* Fixed point arithmetic is overcomplicated, suboptimal and even
+	wrong. Check it later.
+*/
+
+
+/* This number is arbitrary */
+
+#define CSZ_MAX_GUARANTEED 16
+
+#define CSZ_FLOW_ID(skb)   (CSZ_MAX_GUARANTEED)
+
+struct csz_head
+{
+	struct csz_head		*snext;
+	struct csz_head		*sprev;
+	struct csz_head		*fnext;
+	struct csz_head		*fprev;
+};
+
+struct csz_flow
+{
+	struct csz_head		*snext;
+	struct csz_head		*sprev;
+	struct csz_head		*fnext;
+	struct csz_head		*fprev;
+
+/* Parameters */
+	unsigned long		rate;	/* Flow rate. Fixed point is at rate_log */
+	unsigned long		*L_tab;	/* Lookup table for L/(B*r_a) values */
+	unsigned long		max_bytes;	/* Maximal length of queue */
+#ifdef CSZ_PLUS_TBF
+	unsigned long		depth;	/* Depth of token bucket, normalized
+					   as L/(B*r_a) */
+#endif
+
+/* Variables */
+#ifdef CSZ_PLUS_TBF
+	unsigned long		tokens; /* Tokens number: usecs */
+	psched_time_t		t_tbf;
+	unsigned long		R_tbf;
+	int			throttled;
+#endif
+	unsigned		peeked;
+	unsigned long		start;	/* Finish number of the first skb */
+	unsigned long		finish;	/* Finish number of the flow */
+
+	struct sk_buff_head	q;	/* FIFO queue */
+};
+
+#define L2R(q,f,L) ((f)->L_tab[(L)>>(q)->cell_log])
+
+struct csz_sched_data
+{
+/* Parameters */
+	unsigned char	cell_log;	/* 1<<cell_log is quantum of packet size */
+	unsigned char	rate_log;	/* fixed point position for rate;
+					 * really we need not it */
+	unsigned char	R_log;		/* fixed point position for round number */
+	unsigned char	delta_log;	/* 1<<delta_log is maximal timeout in usecs;
+					 * 21 <-> 2.1sec is MAXIMAL value */
+
+/* Variables */
+#ifdef CSZ_PLUS_TBF
+	struct timer_list wd_timer;
+	long		wd_expires;
+#endif
+	psched_time_t	t_c;		/* Time check-point */
+	unsigned long	R_c;		/* R-number check-point	*/
+	unsigned long	rate;		/* Current sum of rates of active flows */
+	struct csz_head	s;		/* Flows sorted by "start" */
+	struct csz_head	f;		/* Flows sorted by "finish"	*/
+
+	struct sk_buff_head	other[4];/* Predicted (0) and the best efforts
+					     classes (1,2,3) */
+	struct csz_flow	flow[CSZ_MAX_GUARANTEED]; /* Array of flows */
+};
+
+/* These routines (csz_insert_finish and csz_insert_start) are
+   the most time consuming part of all the algorithm.
+
+   We insert to sorted list, so that time
+   is linear with respect to number of active flows in the worst case.
+   Note that we have not very large number of guaranteed flows,
+   so that logarithmic algorithms (heap etc.) are useless,
+   they are slower than linear one when length of list <= 32.
+
+   Heap would take sence if we used WFQ for best efforts
+   flows, but SFQ is better choice in this case.
+ */
+
+
+/* Insert flow "this" to the list "b" before
+   flow with greater finish number.
+ */
+
+#if 0
+/* Scan forward */
+extern __inline__ void csz_insert_finish(struct csz_head *b,
+					 struct csz_flow *this)
+{
+	struct csz_head *f = b->fnext;
+	unsigned long finish = this->finish;
+
+	while (f != b) {
+		if (((struct csz_flow*)f)->finish - finish > 0)
+			break;
+		f = f->fnext;
+	}
+	this->fnext = f;
+	this->fprev = f->fprev;
+	this->fnext->fprev = this->fprev->fnext = (struct csz_head*)this;
+}
+#else
+/* Scan backward */
+extern __inline__ void csz_insert_finish(struct csz_head *b,
+					 struct csz_flow *this)
+{
+	struct csz_head *f = b->fprev;
+	unsigned long finish = this->finish;
+
+	while (f != b) {
+		if (((struct csz_flow*)f)->finish - finish <= 0)
+			break;
+		f = f->fprev;
+	}
+	this->fnext = f->fnext;
+	this->fprev = f;
+	this->fnext->fprev = this->fprev->fnext = (struct csz_head*)this;
+}
+#endif
+
+/* Insert flow "this" to the list "b" before
+   flow with greater start number.
+ */
+
+extern __inline__ void csz_insert_start(struct csz_head *b,
+					struct csz_flow *this)
+{
+	struct csz_head *f = b->snext;
+	unsigned long start = this->start;
+
+	while (f != b) {
+		if (((struct csz_flow*)f)->start - start > 0)
+			break;
+		f = f->snext;
+	}
+	this->snext = f;
+	this->sprev = f->sprev;
+	this->snext->sprev = this->sprev->snext = (struct csz_head*)this;
+}
+
+
+/* Calculate and return current round number.
+   It is another time consuming part, but
+   it is impossible to avoid it.
+
+   Fixed point arithmetic is not ... does not ... Well, it is just CRAP.
+ */
+
+static unsigned long csz_update(struct Qdisc *sch)
+{
+	struct csz_sched_data	*q = (struct csz_sched_data*)sch->data;
+	struct csz_flow 	*a;
+	unsigned long		F;
+	unsigned long		tmp;
+	psched_time_t		now;
+	unsigned long		delay;
+	unsigned long		R_c;
+
+	PSCHED_GET_TIME(now);
+	delay = PSCHED_TDIFF_SAFE(now, q->t_c, 0, goto do_reset);
+
+	if (delay>>q->delta_log) {
+do_reset:
+		/* Delta is too large.
+		   It is possible if MTU/BW > 1<<q->delta_log
+		   (i.e. configuration error) or because of hardware
+		   fault. We have no choice...
+		 */
+		qdisc_reset(sch);
+		return 0;
+	}
+
+	q->t_c = now;
+
+	for (;;) {
+		a = (struct csz_flow*)q->f.fnext;
+
+		/* No more active flows. Reset R and exit. */
+		if (a == (struct csz_flow*)&q->f) {
+#ifdef CSZ_DEBUG
+			if (q->rate) {
+				printk("csz_update: rate!=0 on inactive csz\n");
+				q->rate = 0;
+			}
+#endif
+			q->R_c = 0;
+			return 0;
+		}
+
+		F = a->finish;
+
+#ifdef CSZ_DEBUG
+		if (q->rate == 0) {
+			printk("csz_update: rate=0 on active csz\n");
+			goto do_reset;
+		}
+#endif
+
+		/*
+		 *           tmp = (t - q->t_c)/q->rate;
+		 */
+
+		tmp = ((delay<<(31-q->delta_log))/q->rate)>>(31-q->delta_log+q->R_log);
+
+		tmp += q->R_c;
+
+		/* OK, this flow (and all flows with greater
+		   finish numbers) is still active */
+		if (F - tmp > 0)
+			break;
+
+		/* It is more not active */
+
+		a->fprev->fnext = a->fnext;
+		a->fnext->fprev = a->fprev;
+
+		/*
+		 * q->t_c += (F - q->R_c)*q->rate
+		 */
+
+		tmp = ((F-q->R_c)*q->rate)<<q->R_log;
+		R_c = F;
+		q->rate -= a->rate;
+
+		if (delay - tmp >= 0) {
+			delay -= tmp;
+			continue;
+		}
+		delay = 0;
+	}
+
+	q->R_c = tmp;
+	return tmp;
+}
+
+static int
+csz_enqueue(struct sk_buff *skb, struct Qdisc* sch)
+{
+	struct csz_sched_data *q = (struct csz_sched_data *)sch->data;
+	unsigned flow_id = CSZ_FLOW_ID(skb);
+	unsigned long R;
+	int prio;
+	struct csz_flow *this;
+
+	if (flow_id >= CSZ_MAX_GUARANTEED) {
+		prio = flow_id - CSZ_MAX_GUARANTEED;
+		flow_id = 0;
+	}
+
+	this = &q->flow[flow_id];
+	if (this->q.qlen >= this->max_bytes || this->L_tab == NULL) {
+		kfree_skb(skb, FREE_WRITE);
+		return 0;
+	}
+
+	R = csz_update(sch);
+
+	if (this->finish - R >= 0) {
+		/* It was active */
+		this->finish += L2R(q,this,skb->len);
+	} else {
+		/* It is inactive; activate it */
+		this->finish = R + L2R(q,this,skb->len);
+		q->rate += this->rate;
+		csz_insert_finish(&q->f, this);
+	}
+
+	/* If this flow was empty, remember start number
+	   and insert it into start queue */
+	if (this->q.qlen == 0) {
+		this->start = this->finish;
+		csz_insert_start(&q->s, this);
+	}
+	if (flow_id)
+		skb_queue_tail(&this->q, skb);
+	else
+		skb_queue_tail(&q->other[prio], skb);
+	sch->q.qlen++;
+	return 1;
+}
+
+static __inline__ struct sk_buff *
+skb_dequeue_best(struct csz_sched_data * q)
+{
+	int i;
+	struct sk_buff *skb;
+
+	for (i=0; i<4; i++) {
+		skb = skb_dequeue(&q->other[i]);
+		if (skb) {
+			q->flow[0].q.qlen--;
+			return skb;
+		}
+	}
+	return NULL;
+}
+
+static __inline__ struct sk_buff *
+skb_peek_best(struct csz_sched_data * q)
+{
+	int i;
+	struct sk_buff *skb;
+
+	for (i=0; i<4; i++) {
+		skb = skb_peek(&q->other[i]);
+		if (skb)
+			return skb;
+	}
+	return NULL;
+}
+
+#ifdef CSZ_PLUS_TBF
+
+static void csz_watchdog(unsigned long arg)
+{
+	struct Qdisc *sch = (struct Qdisc*)arg;
+	struct csz_sched_data *q = (struct csz_sched_data*)sch->data;
+
+	q->wd_timer.expires = 0;
+	q->wd_timer.function = NULL;
+
+	qdisc_wakeup(sch->dev);
+}
+
+static __inline__ void
+csz_move_queue(struct csz_flow *this, long delta)
+{
+	this->fprev->fnext = this->fnext;
+	this->fnext->fprev = this->fprev;
+
+	this->start += delta;
+	this->finish += delta;
+
+	csz_insert_finish(this);
+}
+
+static __inline__ int csz_enough_tokens(struct csz_sched_data *q,
+					struct csz_flow *this,
+					struct sk_buff *skb)
+{
+	long toks;
+	long shift;
+	psched_time_t now;
+
+	PSCHED_GET_TIME(now);
+
+	toks = PSCHED_TDIFF(now, t_tbf) + this->tokens - L2R(q,this,skb->len);
+
+	shift = 0;
+	if (this->throttled) {
+		/* Remember aposteriory delay */
+
+		unsigned long R = csz_update(q);
+		shift = R - this->R_tbf;
+		this->R_tbf = R;
+	}
+
+	if (toks >= 0) {
+		/* Now we have enough tokens to proceed */
+
+		this->tokens = toks <= this->depth ? toks ? this->depth;
+		this->t_tbf = now;
+	
+		if (!this->throttled)
+			return 1;
+
+		/* Flow was throttled. Update its start&finish numbers
+		   with delay calculated aposteriori.
+		 */
+
+		this->throttled = 0;
+		if (shift > 0)
+			csz_move_queue(this, shift);
+		return 1;
+	}
+
+	if (!this->throttled) {
+		/* Flow has just been throttled; remember
+		   current round number to calculate aposteriori delay
+		 */
+		this->throttled = 1;
+		this->R_tbf = csz_update(q);
+	}
+
+	/* Move all the queue to the time when it will be allowed to send.
+	   We should translate time to round number, but it is impossible,
+	   so that we made the most conservative estimate i.e. we suppose
+	   that only this flow is active and, hence, R = t.
+	   Really toks <= R <= toks/r_a.
+
+	   This apriory shift in R will be adjusted later to reflect
+	   real delay. We cannot avoid it because of:
+	   - throttled flow continues to be active from the viewpoint
+	     of CSZ, so that it would acquire highest priority,
+	     if you not adjusted start numbers.
+	   - Eventually, finish number would become less than round
+	     number and flow were declared inactive.
+	 */
+
+	toks = -toks;
+
+	/* Remeber, that we should start watchdog */
+	if (toks < q->wd_expires)
+		q->wd_expires = toks;
+
+	toks >>= q->R_log;
+	shift += toks;
+	if (shift > 0) {
+		this->R_tbf += toks;
+		csz_move_queue(this, shift);
+	}
+	csz_insert_start(this);
+	return 0;
+}
+#endif
+
+
+static struct sk_buff *
+csz_dequeue(struct Qdisc* sch)
+{
+	struct csz_sched_data *q = (struct csz_sched_data *)sch->data;
+	struct sk_buff *skb;
+	struct csz_flow *this;
+
+#ifdef CSZ_PLUS_TBF
+	q->wd_expires = 0;
+#endif
+	this = (struct csz_flow*)q->s.snext;
+
+	while (this != (struct csz_flow*)&q->s) {
+
+		/* First of all: unlink from start list */
+		this->sprev->snext = this->snext;
+		this->snext->sprev = this->sprev;
+
+		if (this != &q->flow[0]) {	/* Guaranteed flow */
+			skb = __skb_dequeue(&this->q);
+			if (skb) {
+#ifdef CSZ_PLUS_TBF
+				if (this->depth) {
+					if (!csz_enough_tokens(q, this, skb))
+						continue;
+				}
+#endif
+				if (this->q.qlen) {
+					struct sk_buff *nskb = skb_peek(&this->q);
+					this->start += L2R(q,this,nskb->len);
+					csz_insert_start(&q->s, this);
+				}
+				sch->q.qlen--;
+				return skb;
+			}
+		} else {	/* Predicted or best effort flow */
+			skb = skb_dequeue_best(q);
+			if (skb) {
+				unsigned peeked = this->peeked;
+				this->peeked = 0;
+
+				if (--this->q.qlen) {
+					struct sk_buff *nskb;
+					unsigned dequeued = L2R(q,this,skb->len);
+
+					/* We got not the same thing that
+					   peeked earlier; adjust start number
+					   */
+					if (peeked != dequeued && peeked)
+						this->start += dequeued - peeked;
+
+					nskb = skb_peek_best(q);
+					peeked = L2R(q,this,nskb->len);
+					this->start += peeked;
+					this->peeked = peeked;
+					csz_insert_start(&q->s, this);
+				}
+				sch->q.qlen--;
+				return skb;
+			}
+		}
+	}
+#ifdef CSZ_PLUS_TBF
+	/* We are about to return no skb.
+	   Schedule watchdog timer, if it occured because of shaping.
+	 */
+	if (q->wd_expires) {
+		if (q->wd_timer.function)
+			del_timer(&q->wd_timer);
+		q->wd_timer.function = csz_watchdog;
+		q->wd_timer.expires = jiffies + PSCHED_US2JIFFIE(q->wd_expires);
+		add_timer(&q->wd_timer);
+	}
+#endif
+	return NULL;
+}
+
+static void
+csz_reset(struct Qdisc* sch)
+{
+	struct csz_sched_data *q = (struct csz_sched_data *)sch->data;
+	struct sk_buff *skb;
+	int    i;
+
+	for (i=0; i<4; i++)
+		while ((skb=skb_dequeue(&q->other[i])) != NULL)
+			kfree_skb(skb, 0);
+
+	for (i=0; i<CSZ_MAX_GUARANTEED; i++) {
+		struct csz_flow *this = q->flow + i;
+		while ((skb = skb_dequeue(&this->q)) != NULL)
+			kfree_skb(skb, FREE_WRITE);
+		this->snext = this->sprev =
+		this->fnext = this->fprev = (struct csz_head*)this;
+		this->start = this->finish = 0;
+	}
+	q->s.snext = q->s.sprev = &q->s;
+	q->f.fnext = q->f.fprev = &q->f;
+	q->R_c = 0;
+#ifdef CSZ_PLUS_TBF
+	PSCHED_GET_TIME(&q->t_tbf);
+	q->tokens = q->depth;
+	if (q->wd_timer.function) {
+		del_timer(&q->wd_timer);
+		q->wd_timer.function = NULL;
+	}
+#endif
+	sch->q.qlen = 0;
+}
+
+static void
+csz_destroy(struct Qdisc* sch)
+{
+/*
+	struct csz_sched_data *q = (struct csz_sched_data *)sch->data;
+	int	i;
+
+	for (i=0; i<4; i++)
+		qdisc_destroy(q->other[i]);
+ */
+}
+
+static int csz_init(struct Qdisc *sch, void *arg)
+{
+	struct csz_sched_data *q = (struct csz_sched_data *)sch->data;
+	struct cszinitctl *ctl = (struct cszinitctl*)arg;
+	int    i;
+
+	for (i=0; i<4; i++)
+		skb_queue_head_init(&q->other[i]);
+
+	for (i=0; i<CSZ_MAX_GUARANTEED; i++) {
+		struct csz_flow *this = q->flow + i;
+		skb_queue_head_init(&this->q);
+		this->snext = this->sprev =
+		this->fnext = this->fprev = (struct csz_head*)this;
+		this->start = this->finish = 0;
+	}
+	q->s.snext = q->s.sprev = &q->s;
+	q->f.fnext = q->f.fprev = &q->f;
+	q->R_c = 0;
+#ifdef CSZ_PLUS_TBF
+	init_timer(&q->wd_timer);
+	q->wd_timer.data = (unsigned long)sch;
+#endif
+	if (ctl) {
+		if (ctl->flows != CSZ_MAX_GUARANTEED)
+			return -EINVAL;
+		q->cell_log = ctl->cell_log;
+	}
+	return 0;
+}
+
+static int csz_control(struct Qdisc *sch, struct pschedctl *gctl)
+{
+/*
+	struct csz_sched_data *q = (struct csz_sched_data *)sch->data;
+	struct cszctl *ctl = (struct cszctl*)gctl->arg;
+	struct sk_buff *skb;
+	int    i;
+
+	if (op == PSCHED_TC_ATTACH) {
+		
+	}
+*/
+	return 0;
+}
+
+
+
+
+struct Qdisc_ops csz_ops =
+{
+	NULL,
+	"csz",
+	0,
+	sizeof(struct csz_sched_data),
+	csz_enqueue,
+	csz_dequeue,
+	csz_reset,
+	csz_destroy,
+	csz_init,
+	csz_control,
+};
+
+
+#ifdef MODULE
+#include <linux/module.h>
+int init_module(void)
+{
+	int err;
+
+	/* Load once and never free it. */
+	MOD_INC_USE_COUNT;
+
+	err = register_qdisc(&csz_ops);
+	if (err)
+		MOD_DEC_USE_COUNT;
+	return err;
+}
+
+void cleanup_module(void) 
+{
+}
+#endif