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

• Lines: 334
• Date: Sun Nov 30 14:00:40 1997
• Orig file: v2.1.67/linux/net/sched/sch_sfq.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.1.67/linux/net/sched/sch_sfq.c linux/net/sched/sch_sfq.c
@@ -0,0 +1,333 @@
+/*
+ * net/sched/sch_sfq.c	Stochastic Fairness Queueing 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/config.h>
+#include <linux/module.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 <linux/init.h>
+#include <net/ip.h>
+#include <net/route.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <net/pkt_sched.h>
+
+
+/*	Stochastic Fairness Queuing algorithm.
+	=======================================
+
+	Source:
+	Paul E. McKenney "Stochastic Fairness Queuing",
+	IEEE INFOCOMM'90 Proceedings, San Francisco, 1990.
+
+	Paul E. McKenney "Stochastic Fairness Queuing",
+	"Interworking: Research and Experience", v.2, 1991, p.113-131.
+
+
+	See also:
+	M. Shreedhar and George Varghese "Efficient Fair
+	Queuing using Deficit Round Robin", Proc. SIGCOMM 95.
+
+
+	It is not the thing that usually called (W)FQ nowadays. It does not
+	use any timestamp mechanism, but instead processes queues
+	in round-robin order.
+
+	ADVANTAGE:
+
+	- It is very cheap. Both CPU and memory requirements are minimal.
+
+	DRAWBACKS:
+
+	- "Stochastic" -> It is not 100% fair. 
+	When hash collisions occur, several flows are considred as one.
+
+	- "Round-robin" -> It introduces larger delays than virtual clock
+	based schemes, and should not be used for isolation interactive
+	traffic	from non-interactive. It means, that this scheduler
+	should be used as leaf of CBQ or P3, which put interactive traffic
+	to higher priority band.
+
+	We still need true WFQ for top level CSZ, but using WFQ
+	for the best effort traffic is absolutely pointless:
+	SFQ is superior for this purpose.
+
+	IMPLEMENTATION:
+	This implementation limits maximal queue length to 128;
+	maximal mtu to 2^15-1; number of hash buckets to 1024.
+	The only goal of this restrictions was that all data
+	fitted to one 4K page :-). Struct sfq_sched_data is
+	organized in anti-cache manner: all the data for bucket
+	scattered over different locations. It is not good,
+	but it allowed to put it into 4K.
+
+	It is easy to increase these values.
+*/
+
+#define SFQ_DEPTH		128
+#define SFQ_HASH_DIVISOR	1024
+
+#define SFQ_HASH(a)		0
+
+/* This type should contain at least SFQ_DEPTH*2 values */
+typedef unsigned char sfq_index;
+
+struct sfq_head
+{
+	sfq_index	next;
+	sfq_index	prev;
+};
+
+struct sfq_sched_data
+{
+/* Parameters */
+	unsigned	quantum;	/* Allotment per round: MUST BE >= MTU */
+
+/* Variables */
+	sfq_index	tail;		/* Index of current slot in round */
+	sfq_index	max_depth;	/* Maximal depth */
+
+	sfq_index	ht[SFQ_HASH_DIVISOR];	/* Hash table */
+	sfq_index	next[SFQ_DEPTH];	/* Active slots link */
+	short		allot[SFQ_DEPTH];	/* Current allotment per slot */
+	unsigned short	hash[SFQ_DEPTH];	/* Hash value indexed by slots */
+	struct sk_buff_head	qs[SFQ_DEPTH];		/* Slot queue */
+	struct sfq_head	dep[SFQ_DEPTH*2];	/* Linked list of slots, indexed by depth */
+};
+
+extern __inline__ void sfq_link(struct sfq_sched_data *q, sfq_index x)
+{
+	sfq_index p, n;
+	int d = q->qs[x].qlen;
+
+	p = d;
+	n = q->dep[d].next;
+	q->dep[x].next = n;
+	q->dep[x].prev = p;
+	q->dep[p].next = q->dep[n].prev = x;
+}
+
+extern __inline__ void sfq_dec(struct sfq_sched_data *q, sfq_index x)
+{
+	sfq_index p, n;
+
+	n = q->dep[x].next;
+	p = q->dep[x].prev;
+	q->dep[p].next = n;
+	q->dep[n].prev = p;
+
+	if (n == p && q->max_depth == q->qs[x].qlen + 1)
+		q->max_depth--;
+
+	sfq_link(q, x);
+}
+
+extern __inline__ void sfq_inc(struct sfq_sched_data *q, sfq_index x)
+{
+	sfq_index p, n;
+	int d;
+
+	n = q->dep[x].next;
+	p = q->dep[x].prev;
+	q->dep[p].next = n;
+	q->dep[n].prev = p;
+	d = q->qs[x].qlen;
+	if (q->max_depth < d)
+		q->max_depth = d;
+
+	sfq_link(q, x);
+}
+
+static __inline__ void sfq_drop(struct sfq_sched_data *q)
+{
+	struct sk_buff *skb;
+	sfq_index d = q->max_depth;
+
+	/* Queue is full! Find the longest slot and
+	   drop a packet from it */
+
+	if (d != 1) {
+		sfq_index x = q->dep[d].next;
+		skb = q->qs[x].prev;
+		__skb_unlink(skb, &q->qs[x]);
+		kfree_skb(skb, FREE_WRITE);
+		sfq_dec(q, x);
+/*
+		sch->q.qlen--;
+ */
+		return;
+	}
+
+	/* It is difficult to believe, but ALL THE SLOTS HAVE LENGTH 1. */
+
+	d = q->next[q->tail];
+	q->next[q->tail] = q->next[d];
+	q->allot[q->next[d]] += q->quantum;
+	skb = q->qs[d].prev;
+	__skb_unlink(skb, &q->qs[d]);
+	kfree_skb(skb, FREE_WRITE);
+	sfq_dec(q, d);
+/*
+	sch->q.qlen--;
+ */
+	q->ht[q->hash[d]] = SFQ_DEPTH;
+	return;
+}
+
+static int
+sfq_enqueue(struct sk_buff *skb, struct Qdisc* sch)
+{
+	struct sfq_sched_data *q = (struct sfq_sched_data *)sch->data;
+	unsigned hash = SFQ_HASH(skb);
+	sfq_index x;
+
+	x = q->ht[hash];
+	if (x == SFQ_DEPTH) {
+		q->ht[hash] = x = q->dep[SFQ_DEPTH].next;
+		q->hash[x] = hash;
+	}
+	__skb_queue_tail(&q->qs[x], skb);
+	sfq_inc(q, x);
+	if (q->qs[x].qlen == 1) {		/* The flow is new */
+		if (q->tail == SFQ_DEPTH) {	/* It is the first flow */
+			q->tail = x;
+			q->next[x] = x;
+			q->allot[x] = q->quantum;
+		} else {
+			q->next[x] = q->next[q->tail];
+			q->next[q->tail] = x;
+			q->tail = x;
+		}
+	}
+	if (++sch->q.qlen < SFQ_DEPTH-1)
+		return 1;
+
+	sfq_drop(q);
+	return 0;
+}
+
+static struct sk_buff *
+sfq_dequeue(struct Qdisc* sch)
+{
+	struct sfq_sched_data *q = (struct sfq_sched_data *)sch->data;
+	struct sk_buff *skb;
+	sfq_index a, old_a;
+
+	/* No active slots */
+	if (q->tail == SFQ_DEPTH)
+		return NULL;
+
+	a = old_a = q->next[q->tail];
+
+	/* Grab packet */
+	skb = __skb_dequeue(&q->qs[a]);
+	sfq_dec(q, a);
+	sch->q.qlen--;
+
+	/* Is the slot empty? */
+	if (q->qs[a].qlen == 0) {
+		a = q->next[a];
+		if (a == old_a) {
+			q->tail = SFQ_DEPTH;
+			return skb;
+		}
+		q->next[q->tail] = a;
+		q->allot[a] += q->quantum;
+	} else if ((q->allot[a] -= skb->len) <= 0) {
+		q->tail = a;
+		a = q->next[a];
+		q->allot[a] += q->quantum;
+	}
+	return skb;
+}
+
+static void
+sfq_reset(struct Qdisc* sch)
+{
+	struct sk_buff *skb;
+
+	while ((skb = sfq_dequeue(sch)) != NULL)
+		kfree_skb(skb, FREE_WRITE);
+}
+
+
+static int sfq_open(struct Qdisc *sch, void *arg)
+{
+	struct sfq_sched_data *q;
+	int i;
+
+	q = (struct sfq_sched_data *)sch->data;
+
+	for (i=0; i<SFQ_HASH_DIVISOR; i++)
+		q->ht[i] = SFQ_DEPTH;
+	for (i=0; i<SFQ_DEPTH; i++) {
+		skb_queue_head_init(&q->qs[i]);
+		q->dep[i+SFQ_DEPTH].next = i+SFQ_DEPTH;
+		q->dep[i+SFQ_DEPTH].prev = i+SFQ_DEPTH;
+	}
+	q->max_depth = 0;
+	q->tail = SFQ_DEPTH;
+	q->quantum = sch->dev->mtu;
+	if (sch->dev->hard_header)
+		q->quantum += sch->dev->hard_header_len;
+	for (i=0; i<SFQ_DEPTH; i++)
+		sfq_link(q, i);
+	return 0;
+}
+
+
+struct Qdisc_ops sfq_ops =
+{
+	NULL,
+	"sfq",
+	0,
+	sizeof(struct sfq_sched_data),
+	sfq_enqueue,
+	sfq_dequeue,
+	sfq_reset,
+	NULL,
+	sfq_open,
+};
+
+#ifdef MODULE
+int init_module(void)
+{
+	int err;
+
+	/* Load once and never free it. */
+	MOD_INC_USE_COUNT;
+
+	err = register_qdisc(&sfq_ops);
+	if (err)
+		MOD_DEC_USE_COUNT;
+	return err;
+}
+
+void cleanup_module(void) 
+{
+}
+#endif