sch_cbq.c

Linux内核源代码 为压缩文件 是<<Linux内核>>一书中的源代码

/*
 * net/sched/sch_cbq.c	Class-Based Queueing discipline.
 *
 *		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, <[e-mail]>
 *
 */

#include <linux/config.h>
#include <linux/module.h>
#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>


/*	Class-Based Queueing (CBQ) algorithm.
	=======================================

	Sources: [1] Sally Floyd and Van Jacobson, "Link-sharing and Resource
	         Management Models for Packet Networks",
		 IEEE/ACM Transactions on Networking, Vol.3, No.4, 1995

	         [2] Sally Floyd, "Notes on CBQ and Guaranted Service", 1995

	         [3] Sally Floyd, "Notes on Class-Based Queueing: Setting
		 Parameters", 1996

		 [4] Sally Floyd and Michael Speer, "Experimental Results
		 for Class-Based Queueing", 1998, not published.

	-----------------------------------------------------------------------

	Algorithm skeleton was taken from NS simulator cbq.cc.
	If someone wants to check this code against the LBL version,
	he should take into account that ONLY the skeleton was borrowed,
	the implementation is different. Particularly:

	--- The WRR algorithm is different. Our version looks more
        reasonable (I hope) and works when quanta are allowed to be
        less than MTU, which is always the case when real time classes
        have small rates. Note, that the statement of [3] is
        incomplete, delay may actually be estimated even if class
        per-round allotment is less than MTU. Namely, if per-round
        allotment is W*r_i, and r_1+...+r_k = r < 1

	delay_i <= ([MTU/(W*r_i)]*W*r + W*r + k*MTU)/B

	In the worst case we have IntServ estimate with D = W*r+k*MTU
	and C = MTU*r. The proof (if correct at all) is trivial.


	--- It seems that cbq-2.0 is not very accurate. At least, I cannot
	interpret some places, which look like wrong translations
	from NS. Anyone is advised to find these differences
	and explain to me, why I am wrong 8).

	--- Linux has no EOI event, so that we cannot estimate true class
	idle time. Workaround is to consider the next dequeue event
	as sign that previous packet is finished. This is wrong because of
	internal device queueing, but on a permanently loaded link it is true.
	Moreover, combined with clock integrator, this scheme looks
	very close to an ideal solution.  */

struct cbq_sched_data;


struct cbq_class
{
	struct cbq_class	*next;		/* hash table link */
	struct cbq_class	*next_alive;	/* next class with backlog in this priority band */

/* Parameters */
	u32			classid;
	unsigned char		priority;	/* class priority */
	unsigned char		priority2;	/* priority to be used after overlimit */
	unsigned char		ewma_log;	/* time constant for idle time calculation */
	unsigned char		ovl_strategy;
#ifdef CONFIG_NET_CLS_POLICE
	unsigned char		police;
#endif

	u32			defmap;

	/* Link-sharing scheduler parameters */
	long			maxidle;	/* Class paramters: see below. */
	long			offtime;
	long			minidle;
	u32			avpkt;
	struct qdisc_rate_table	*R_tab;

	/* Overlimit strategy parameters */
	void			(*overlimit)(struct cbq_class *cl);
	long			penalty;

	/* General scheduler (WRR) parameters */
	long			allot;
	long			quantum;	/* Allotment per WRR round */
	long			weight;		/* Relative allotment: see below */

	struct Qdisc		*qdisc;		/* Ptr to CBQ discipline */
	struct cbq_class	*split;		/* Ptr to split node */
	struct cbq_class	*share;		/* Ptr to LS parent in the class tree */
	struct cbq_class	*tparent;	/* Ptr to tree parent in the class tree */
	struct cbq_class	*borrow;	/* NULL if class is bandwidth limited;
						   parent otherwise */
	struct cbq_class	*sibling;	/* Sibling chain */
	struct cbq_class	*children;	/* Pointer to children chain */

	struct Qdisc		*q;		/* Elementary queueing discipline */


/* Variables */
	unsigned char		cpriority;	/* Effective priority */
	unsigned char		delayed;
	unsigned char		level;		/* level of the class in hierarchy:
						   0 for leaf classes, and maximal
						   level of children + 1 for nodes.
						 */

	psched_time_t		last;		/* Last end of service */
	psched_time_t		undertime;
	long			avgidle;
	long			deficit;	/* Saved deficit for WRR */
	unsigned long		penalized;
	struct tc_stats		stats;
	struct tc_cbq_xstats	xstats;

	struct tcf_proto	*filter_list;

	int			refcnt;
	int			filters;

	struct cbq_class 	*defaults[TC_PRIO_MAX+1];
};

struct cbq_sched_data
{
	struct cbq_class	*classes[16];		/* Hash table of all classes */
	int			nclasses[TC_CBQ_MAXPRIO+1];
	unsigned		quanta[TC_CBQ_MAXPRIO+1];

	struct cbq_class	link;

	unsigned		activemask;
	struct cbq_class	*active[TC_CBQ_MAXPRIO+1];	/* List of all classes
								   with backlog */

#ifdef CONFIG_NET_CLS_POLICE
	struct cbq_class	*rx_class;
#endif
	struct cbq_class	*tx_class;
	struct cbq_class	*tx_borrowed;
	int			tx_len;
	psched_time_t		now;		/* Cached timestamp */
	psched_time_t		now_rt;		/* Cached real time */
	unsigned		pmask;

	struct timer_list	delay_timer;
	struct timer_list	wd_timer;	/* Watchdog timer,
						   started when CBQ has
						   backlog, but cannot
						   transmit just now */
	long			wd_expires;
	int			toplevel;
	u32			hgenerator;
};


#define L2T(cl,len)	((cl)->R_tab->data[(len)>>(cl)->R_tab->rate.cell_log])


static __inline__ unsigned cbq_hash(u32 h)
{
	h ^= h>>8;
	h ^= h>>4;
	return h&0xF;
}

static __inline__ struct cbq_class *
cbq_class_lookup(struct cbq_sched_data *q, u32 classid)
{
	struct cbq_class *cl;

	for (cl = q->classes[cbq_hash(classid)]; cl; cl = cl->next)
		if (cl->classid == classid)
			return cl;
	return NULL;
}

#ifdef CONFIG_NET_CLS_POLICE

static struct cbq_class *
cbq_reclassify(struct sk_buff *skb, struct cbq_class *this)
{
	struct cbq_class *cl, *new;

	for (cl = this->tparent; cl; cl = cl->tparent)
		if ((new = cl->defaults[TC_PRIO_BESTEFFORT]) != NULL && new != this)
			return new;

	return NULL;
}

#endif

/* Classify packet. The procedure is pretty complicated, but
   it allows us to combine link sharing and priority scheduling
   transparently.

   Namely, you can put link sharing rules (f.e. route based) at root of CBQ,
   so that it resolves to split nodes. Then packets are classified
   by logical priority, or a more specific classifier may be attached
   to the split node.
 */

static struct cbq_class *
cbq_classify(struct sk_buff *skb, struct Qdisc *sch)
{
	struct cbq_sched_data *q = (struct cbq_sched_data*)sch->data;
	struct cbq_class *head = &q->link;
	struct cbq_class **defmap;
	struct cbq_class *cl = NULL;
	u32 prio = skb->priority;
	struct tcf_result res;

	/*
	 *  Step 1. If skb->priority points to one of our classes, use it.
	 */
	if (TC_H_MAJ(prio^sch->handle) == 0 &&
	    (cl = cbq_class_lookup(q, prio)) != NULL)
			return cl;

	for (;;) {
		int result = 0;

		defmap = head->defaults;

		/*
		 * Step 2+n. Apply classifier.
		 */
		if (!head->filter_list || (result = tc_classify(skb, head->filter_list, &res)) < 0)
			goto fallback;

		if ((cl = (void*)res.class) == NULL) {
			if (TC_H_MAJ(res.classid))
				cl = cbq_class_lookup(q, res.classid);
			else if ((cl = defmap[res.classid&TC_PRIO_MAX]) == NULL)
				cl = defmap[TC_PRIO_BESTEFFORT];

			if (cl == NULL || cl->level >= head->level)
				goto fallback;
		}

#ifdef CONFIG_NET_CLS_POLICE
		switch (result) {
		case TC_POLICE_RECLASSIFY:
			return cbq_reclassify(skb, cl);
		case TC_POLICE_SHOT:
			return NULL;
		default:
		}
#endif
		if (cl->level == 0)
			return cl;

		/*
		 * Step 3+n. If classifier selected a link sharing class,
		 *	   apply agency specific classifier.
		 *	   Repeat this procdure until we hit a leaf node.
		 */
		head = cl;
	}

fallback:
	cl = head;

	/*
	 * Step 4. No success...
	 */
	if (TC_H_MAJ(prio) == 0 &&
	    !(cl = head->defaults[prio&TC_PRIO_MAX]) &&
	    !(cl = head->defaults[TC_PRIO_BESTEFFORT]))
		return head;

	return cl;
}

/*
   A packet has just been enqueued on the empty class.
   cbq_activate_class adds it to the tail of active class list
   of its priority band.
 */

static __inline__ void cbq_activate_class(struct cbq_class *cl)
{
	struct cbq_sched_data *q = (struct cbq_sched_data*)cl->qdisc->data;
	int prio = cl->cpriority;
	struct cbq_class *cl_tail;

	cl_tail = q->active[prio];
	q->active[prio] = cl;

	if (cl_tail != NULL) {
		cl->next_alive = cl_tail->next_alive;
		cl_tail->next_alive = cl;
	} else {
		cl->next_alive = cl;
		q->activemask |= (1<<prio);
	}
}

/*
   Unlink class from active chain.
   Note that this same procedure is done directly in cbq_dequeue*
   during round-robin procedure.
 */

static void cbq_deactivate_class(struct cbq_class *this)
{
	struct cbq_sched_data *q = (struct cbq_sched_data*)this->qdisc->data;
	int prio = this->cpriority;
	struct cbq_class *cl;
	struct cbq_class *cl_prev = q->active[prio];

	do {
		cl = cl_prev->next_alive;
		if (cl == this) {
			cl_prev->next_alive = cl->next_alive;
			cl->next_alive = NULL;

			if (cl == q->active[prio]) {
				q->active[prio] = cl_prev;
				if (cl == q->active[prio]) {
					q->active[prio] = NULL;
					q->activemask &= ~(1<<prio);
					return;
				}
			}

			cl = cl_prev->next_alive;
			return;
		}
	} while ((cl_prev = cl) != q->active[prio]);
}

static void
cbq_mark_toplevel(struct cbq_sched_data *q, struct cbq_class *cl)
{
	int toplevel = q->toplevel;

	if (toplevel > cl->level && !(cl->q->flags&TCQ_F_THROTTLED)) {
		psched_time_t now;
		psched_tdiff_t incr;

		PSCHED_GET_TIME(now);
		incr = PSCHED_TDIFF(now, q->now_rt);
		PSCHED_TADD2(q->now, incr, now);

		do {
			if (PSCHED_TLESS(cl->undertime, now)) {
				q->toplevel = cl->level;
				return;
			}
		} while ((cl=cl->borrow) != NULL && toplevel > cl->level);
	}
}

static int
cbq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
{
	struct cbq_sched_data *q = (struct cbq_sched_data *)sch->data;
	struct cbq_class *cl = cbq_classify(skb, sch);
	int len = skb->len;
	int ret = NET_XMIT_POLICED;

#ifdef CONFIG_NET_CLS_POLICE
	q->rx_class = cl;
#endif
	if (cl) {
#ifdef CONFIG_NET_CLS_POLICE
		cl->q->__parent = sch;
#endif
		if ((ret = cl->q->enqueue(skb, cl->q)) == 0) {
			sch->q.qlen++;
			sch->stats.packets++;
			sch->stats.bytes+=len;
			cbq_mark_toplevel(q, cl);
			if (!cl->next_alive)
				cbq_activate_class(cl);
			return 0;
		}
	}

	sch->stats.drops++;
	if (cl == NULL)
		kfree_skb(skb);
	else {
		cbq_mark_toplevel(q, cl);
		cl->stats.drops++;
	}
	return ret;
}

static int
cbq_requeue(struct sk_buff *skb, struct Qdisc *sch)
{
	struct cbq_sched_data *q = (struct cbq_sched_data *)sch->data;
	struct cbq_class *cl;
	int ret;

	if ((cl = q->tx_class) == NULL) {
		kfree_skb(skb);
		sch->stats.drops++;
		return NET_XMIT_CN;
	}
	q->tx_class = NULL;

	cbq_mark_toplevel(q, cl);

#ifdef CONFIG_NET_CLS_POLICE
	q->rx_class = cl;
	cl->q->__parent = sch;
#endif
	if ((ret = cl->q->ops->requeue(skb, cl->q)) == 0) {
		sch->q.qlen++;
		if (!cl->next_alive)
			cbq_activate_class(cl);
		return 0;
	}
	sch->stats.drops++;
	cl->stats.drops++;
	return ret;
}

/* Overlimit actions */

/* TC_CBQ_OVL_CLASSIC: (default) penalize leaf class by adding offtime */

static void cbq_ovl_classic(struct cbq_class *cl)
{
	struct cbq_sched_data *q = (struct cbq_sched_data *)cl->qdisc->data;
	psched_tdiff_t delay = PSCHED_TDIFF(cl->undertime, q->now);

	if (!cl->delayed) {
		delay += cl->offtime;

		/* 
		   Class goes to sleep, so that it will have no
		   chance to work avgidle. Let's forgive it 8)

		   BTW cbq-2.0 has a crap in this
		   place, apparently they forgot to shift it by cl->ewma_log.
		 */
		if (cl->avgidle < 0)
			delay -= (-cl->avgidle) - ((-cl->avgidle) >> cl->ewma_log);
		if (cl->avgidle < cl->minidle)
			cl->avgidle = cl->minidle;
		if (delay <= 0)
			delay = 1;
		PSCHED_TADD2(q->now, delay, cl->undertime);

		cl->xstats.overactions++;
		cl->delayed = 1;
	}
	if (q->wd_expires == 0 || q->wd_expires > delay)
		q->wd_expires = delay;

	/* Dirty work! We must schedule wakeups based on
	   real available rate, rather than leaf rate,
	   which may be tiny (even zero).
	 */
	if (q->toplevel == TC_CBQ_MAXLEVEL) {
		struct cbq_class *b;
		psched_tdiff_t base_delay = q->wd_expires;

		for (b = cl->borrow; b; b = b->borrow) {
			delay = PSCHED_TDIFF(b->undertime, q->now);
			if (delay < base_delay) {
				if (delay <= 0)
					delay = 1;
				base_delay = delay;
			}
		}

		q->wd_expires = delay;
	}
}

/* TC_CBQ_OVL_RCLASSIC: penalize by offtime classes in hierarchy, when
   they go overlimit
 */

static void cbq_ovl_rclassic(struct cbq_class *cl)
{
	struct cbq_sched_data *q = (struct cbq_sched_data *)cl->qdisc->data;
	struct cbq_class *this = cl;

	do {
		if (cl->level > q->toplevel) {
			cl = NULL;
			break;
		}
	} while ((cl = cl->borrow) != NULL);

	if (cl == NULL)