Commit 92651940 authored by Alexander Duyck's avatar Alexander Duyck Committed by David S. Miller
Browse files

pkt_sched: Add multiqueue scheduler support 



This patch is intended to add a qdisc to support the new tx multiqueue
architecture by providing a band for each hardware queue.  By doing
this it is possible to support a different qdisc per physical hardware
queue.

This qdisc uses the skb->queue_mapping to select which band to place
the traffic onto.  It then uses a round robin w/ a check to see if the
subqueue is stopped to determine which band to dequeue the packet from.

Signed-off-by: default avatarAlexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 78d15e82

Documentation/networking/multiqueue.txt

+46 −1
Original line number Diff line number Diff line
@@ -24,4 +24,49 @@ netif_{start|stop|wake}_subqueue() functions to manage each queue while the 
device is still operational.  netdev->queue_lock is still used when the device

comes online or when it's completely shut down (unregister_netdev(), etc.).



Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com>
 


Section 2: Qdisc support for multiqueue devices



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



Currently two qdiscs support multiqueue devices.  The first is the default

pfifo_fast qdisc.  This qdisc supports one qdisc per hardware queue.  A new

round-robin qdisc, sch_multiq also supports multiple hardware queues. The

qdisc is responsible for classifying the skb's and then directing the skb's to

bands and queues based on the value in skb->queue_mapping.  Use this field in

the base driver to determine which queue to send the skb to.



sch_multiq has been added for hardware that wishes to avoid unnecessary

requeuing.  It will cycle though the bands and verify that the hardware queue

associated with the band is not stopped prior to dequeuing a packet.



On qdisc load, the number of bands is based on the number of queues on the

hardware.  Once the association is made, any skb with skb->queue_mapping set,

will be queued to the band associated with the hardware queue.





Section 3: Brief howto using MULTIQ for multiqueue devices

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



The userspace command 'tc,' part of the iproute2 package, is used to configure

qdiscs.  To add the MULTIQ qdisc to your network device, assuming the device

is called eth0, run the following command:



# tc qdisc add dev eth0 root handle 1: multiq



The qdisc will allocate the number of bands to equal the number of queues that

the device reports, and bring the qdisc online.  Assuming eth0 has 4 Tx

queues, the band mapping would look like:



band 0 => queue 0

band 1 => queue 1

band 2 => queue 2

band 3 => queue 3



Traffic will begin flowing through each queue if your base device has either

the default simple_tx_hash or a custom netdev->select_queue() defined.



The behavior of tc filters remains the same.



Author: Alexander Duyck <alexander.h.duyck@intel.com>

Original Author: Peter P. Waskiewicz Jr. <peter.p.waskiewicz.jr@intel.com>

include/linux/pkt_sched.h

+7 −0
Original line number Diff line number Diff line
@@ -123,6 +123,13 @@ struct tc_prio_qopt 
	__u8	priomap[TC_PRIO_MAX+1];	/* Map: logical priority -> PRIO band */

};



/* MULTIQ section */



struct tc_multiq_qopt {

	__u16	bands;			/* Number of bands */

	__u16	max_bands;		/* Maximum number of queues */

};



/* TBF section */



struct tc_tbf_qopt

net/sched/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -106,6 +106,15 @@ config NET_SCH_PRIO 
	  To compile this code as a module, choose M here: the

	  module will be called sch_prio.



config NET_SCH_MULTIQ

	tristate "Hardware Multiqueue-aware Multi Band Queuing (MULTIQ)"

	---help---

	  Say Y here if you want to use an n-band queue packet scheduler

	  to support devices that have multiple hardware transmit queues.



	  To compile this code as a module, choose M here: the

	  module will be called sch_multiq.



config NET_SCH_RED

	tristate "Random Early Detection (RED)"

	---help---

net/sched/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ obj-$(CONFIG_NET_SCH_SFQ) += sch_sfq.o 
obj-$(CONFIG_NET_SCH_TBF)	+= sch_tbf.o

obj-$(CONFIG_NET_SCH_TEQL)	+= sch_teql.o

obj-$(CONFIG_NET_SCH_PRIO)	+= sch_prio.o

obj-$(CONFIG_NET_SCH_MULTIQ)	+= sch_multiq.o

obj-$(CONFIG_NET_SCH_ATM)	+= sch_atm.o

obj-$(CONFIG_NET_SCH_NETEM)	+= sch_netem.o

obj-$(CONFIG_NET_CLS_U32)	+= cls_u32.o

net/sched/sch_multiq.c

0 → 100644
+467 −0
Original line number Diff line number Diff line 
/*

 * Copyright (c) 2008, Intel Corporation.

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms and conditions of the GNU General Public License,

 * version 2, as published by the Free Software Foundation.

 *

 * This program is distributed in the hope it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for

 * more details.

 *

 * You should have received a copy of the GNU General Public License along with

 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple

 * Place - Suite 330, Boston, MA 02111-1307 USA.

 *

 * Author: Alexander Duyck <alexander.h.duyck@intel.com>

 */



#include <linux/module.h>

#include <linux/types.h>

#include <linux/kernel.h>

#include <linux/string.h>

#include <linux/errno.h>

#include <linux/skbuff.h>

#include <net/netlink.h>

#include <net/pkt_sched.h>





struct multiq_sched_data {

	u16 bands;

	u16 max_bands;

	u16 curband;

	struct tcf_proto *filter_list;

	struct Qdisc **queues;

};





static struct Qdisc *

multiq_classify(struct sk_buff *skb, struct Qdisc *sch, int *qerr)

{

	struct multiq_sched_data *q = qdisc_priv(sch);

	u32 band;

	struct tcf_result res;

	int err;



	*qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;

	err = tc_classify(skb, q->filter_list, &res);

#ifdef CONFIG_NET_CLS_ACT

	switch (err) {

	case TC_ACT_STOLEN:

	case TC_ACT_QUEUED:

		*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;

	case TC_ACT_SHOT:

		return NULL;

	}

#endif

	band = skb_get_queue_mapping(skb);



	if (band >= q->bands)

		return q->queues[0];



	return q->queues[band];

}



static int

multiq_enqueue(struct sk_buff *skb, struct Qdisc *sch)

{

	struct Qdisc *qdisc;

	int ret;



	qdisc = multiq_classify(skb, sch, &ret);

#ifdef CONFIG_NET_CLS_ACT

	if (qdisc == NULL) {



		if (ret & __NET_XMIT_BYPASS)

			sch->qstats.drops++;

		kfree_skb(skb);

		return ret;

	}

#endif



	ret = qdisc_enqueue(skb, qdisc);

	if (ret == NET_XMIT_SUCCESS) {

		sch->bstats.bytes += qdisc_pkt_len(skb);

		sch->bstats.packets++;

		sch->q.qlen++;

		return NET_XMIT_SUCCESS;

	}

	if (net_xmit_drop_count(ret))

		sch->qstats.drops++;

	return ret;

}





static int

multiq_requeue(struct sk_buff *skb, struct Qdisc *sch)

{

	struct Qdisc *qdisc;

	int ret;



	qdisc = multiq_classify(skb, sch, &ret);

#ifdef CONFIG_NET_CLS_ACT

	if (qdisc == NULL) {

		if (ret & __NET_XMIT_BYPASS)

			sch->qstats.drops++;

		kfree_skb(skb);

		return ret;

	}

#endif



	ret = qdisc->ops->requeue(skb, qdisc);

	if (ret == NET_XMIT_SUCCESS) {

		sch->q.qlen++;

		sch->qstats.requeues++;

		return NET_XMIT_SUCCESS;

	}

	if (net_xmit_drop_count(ret))

		sch->qstats.drops++;

	return ret;

}





static struct sk_buff *multiq_dequeue(struct Qdisc *sch)

{

	struct multiq_sched_data *q = qdisc_priv(sch);

	struct Qdisc *qdisc;

	struct sk_buff *skb;

	int band;



	for (band = 0; band < q->bands; band++) {

		/* cycle through bands to ensure fairness */

		q->curband++;

		if (q->curband >= q->bands)

			q->curband = 0;



		/* Check that target subqueue is available before

		 * pulling an skb to avoid excessive requeues

		 */

		if (!__netif_subqueue_stopped(qdisc_dev(sch), q->curband)) {

			qdisc = q->queues[q->curband];

			skb = qdisc->dequeue(qdisc);

			if (skb) {

				sch->q.qlen--;

				return skb;

			}

		}

	}

	return NULL;



}



static unsigned int multiq_drop(struct Qdisc *sch)

{

	struct multiq_sched_data *q = qdisc_priv(sch);

	int band;

	unsigned int len;

	struct Qdisc *qdisc;



	for (band = q->bands-1; band >= 0; band--) {

		qdisc = q->queues[band];

		if (qdisc->ops->drop) {

			len = qdisc->ops->drop(qdisc);

			if (len != 0) {

				sch->q.qlen--;

				return len;

			}

		}

	}

	return 0;

}





static void

multiq_reset(struct Qdisc *sch)

{

	u16 band;

	struct multiq_sched_data *q = qdisc_priv(sch);



	for (band = 0; band < q->bands; band++)

		qdisc_reset(q->queues[band]);

	sch->q.qlen = 0;

	q->curband = 0;

}



static void

multiq_destroy(struct Qdisc *sch)

{

	int band;

	struct multiq_sched_data *q = qdisc_priv(sch);



	tcf_destroy_chain(&q->filter_list);

	for (band = 0; band < q->bands; band++)

		qdisc_destroy(q->queues[band]);



	kfree(q->queues);

}



static int multiq_tune(struct Qdisc *sch, struct nlattr *opt)

{

	struct multiq_sched_data *q = qdisc_priv(sch);

	struct tc_multiq_qopt *qopt;

	int i;



	if (!netif_is_multiqueue(qdisc_dev(sch)))

		return -EINVAL;

	if (nla_len(opt) < sizeof(*qopt))

		return -EINVAL;



	qopt = nla_data(opt);



	qopt->bands = qdisc_dev(sch)->real_num_tx_queues;



	sch_tree_lock(sch);

	q->bands = qopt->bands;

	for (i = q->bands; i < q->max_bands; i++) {

		struct Qdisc *child = xchg(&q->queues[i], &noop_qdisc);

		if (child != &noop_qdisc) {

			qdisc_tree_decrease_qlen(child, child->q.qlen);

			qdisc_destroy(child);

		}

	}



	sch_tree_unlock(sch);



	for (i = 0; i < q->bands; i++) {

		if (q->queues[i] == &noop_qdisc) {

			struct Qdisc *child;

			child = qdisc_create_dflt(qdisc_dev(sch),

						  sch->dev_queue,

						  &pfifo_qdisc_ops,

						  TC_H_MAKE(sch->handle,

							    i + 1));

			if (child) {

				sch_tree_lock(sch);

				child = xchg(&q->queues[i], child);



				if (child != &noop_qdisc) {

					qdisc_tree_decrease_qlen(child,

								 child->q.qlen);

					qdisc_destroy(child);

				}

				sch_tree_unlock(sch);

			}

		}

	}

	return 0;

}



static int multiq_init(struct Qdisc *sch, struct nlattr *opt)

{

	struct multiq_sched_data *q = qdisc_priv(sch);

	int i;



	q->queues = NULL;



	if (opt == NULL)

		return -EINVAL;



	q->max_bands = qdisc_dev(sch)->num_tx_queues;



	q->queues = kcalloc(q->max_bands, sizeof(struct Qdisc *), GFP_KERNEL);

	if (!q->queues)

		return -ENOBUFS;

	for (i = 0; i < q->max_bands; i++)

		q->queues[i] = &noop_qdisc;



	return multiq_tune(sch, opt);

}



static int multiq_dump(struct Qdisc *sch, struct sk_buff *skb)

{

	struct multiq_sched_data *q = qdisc_priv(sch);

	unsigned char *b = skb_tail_pointer(skb);

	struct tc_multiq_qopt opt;



	opt.bands = q->bands;

	opt.max_bands = q->max_bands;



	NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);



	return skb->len;



nla_put_failure:

	nlmsg_trim(skb, b);

	return -1;

}



static int multiq_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,

		      struct Qdisc **old)

{

	struct multiq_sched_data *q = qdisc_priv(sch);

	unsigned long band = arg - 1;



	if (band >= q->bands)

		return -EINVAL;



	if (new == NULL)

		new = &noop_qdisc;



	sch_tree_lock(sch);

	*old = q->queues[band];

	q->queues[band] = new;

	qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);

	qdisc_reset(*old);

	sch_tree_unlock(sch);



	return 0;

}



static struct Qdisc *

multiq_leaf(struct Qdisc *sch, unsigned long arg)

{

	struct multiq_sched_data *q = qdisc_priv(sch);

	unsigned long band = arg - 1;



	if (band >= q->bands)

		return NULL;



	return q->queues[band];

}



static unsigned long multiq_get(struct Qdisc *sch, u32 classid)

{

	struct multiq_sched_data *q = qdisc_priv(sch);

	unsigned long band = TC_H_MIN(classid);



	if (band - 1 >= q->bands)

		return 0;

	return band;

}



static unsigned long multiq_bind(struct Qdisc *sch, unsigned long parent,

				 u32 classid)

{

	return multiq_get(sch, classid);

}





static void multiq_put(struct Qdisc *q, unsigned long cl)

{

	return;

}



static int multiq_change(struct Qdisc *sch, u32 handle, u32 parent,

			 struct nlattr **tca, unsigned long *arg)

{

	unsigned long cl = *arg;

	struct multiq_sched_data *q = qdisc_priv(sch);



	if (cl - 1 > q->bands)

		return -ENOENT;

	return 0;

}



static int multiq_delete(struct Qdisc *sch, unsigned long cl)

{

	struct multiq_sched_data *q = qdisc_priv(sch);

	if (cl - 1 > q->bands)

		return -ENOENT;

	return 0;

}





static int multiq_dump_class(struct Qdisc *sch, unsigned long cl,

			     struct sk_buff *skb, struct tcmsg *tcm)

{

	struct multiq_sched_data *q = qdisc_priv(sch);



	if (cl - 1 > q->bands)

		return -ENOENT;

	tcm->tcm_handle |= TC_H_MIN(cl);

	if (q->queues[cl-1])

		tcm->tcm_info = q->queues[cl-1]->handle;

	return 0;

}



static int multiq_dump_class_stats(struct Qdisc *sch, unsigned long cl,

				 struct gnet_dump *d)

{

	struct multiq_sched_data *q = qdisc_priv(sch);

	struct Qdisc *cl_q;



	cl_q = q->queues[cl - 1];

	if (gnet_stats_copy_basic(d, &cl_q->bstats) < 0 ||

	    gnet_stats_copy_queue(d, &cl_q->qstats) < 0)

		return -1;



	return 0;

}



static void multiq_walk(struct Qdisc *sch, struct qdisc_walker *arg)

{

	struct multiq_sched_data *q = qdisc_priv(sch);

	int band;



	if (arg->stop)

		return;



	for (band = 0; band < q->bands; band++) {

		if (arg->count < arg->skip) {

			arg->count++;

			continue;

		}

		if (arg->fn(sch, band+1, arg) < 0) {

			arg->stop = 1;

			break;

		}

		arg->count++;

	}

}



static struct tcf_proto **multiq_find_tcf(struct Qdisc *sch, unsigned long cl)

{

	struct multiq_sched_data *q = qdisc_priv(sch);



	if (cl)

		return NULL;

	return &q->filter_list;

}



static const struct Qdisc_class_ops multiq_class_ops = {

	.graft		=	multiq_graft,

	.leaf		=	multiq_leaf,

	.get		=	multiq_get,

	.put		=	multiq_put,

	.change		=	multiq_change,

	.delete		=	multiq_delete,

	.walk		=	multiq_walk,

	.tcf_chain	=	multiq_find_tcf,

	.bind_tcf	=	multiq_bind,

	.unbind_tcf	=	multiq_put,

	.dump		=	multiq_dump_class,

	.dump_stats	=	multiq_dump_class_stats,

};



static struct Qdisc_ops multiq_qdisc_ops __read_mostly = {

	.next		=	NULL,

	.cl_ops		=	&multiq_class_ops,

	.id		=	"multiq",

	.priv_size	=	sizeof(struct multiq_sched_data),

	.enqueue	=	multiq_enqueue,

	.dequeue	=	multiq_dequeue,

	.requeue	=	multiq_requeue,

	.drop		=	multiq_drop,

	.init		=	multiq_init,

	.reset		=	multiq_reset,

	.destroy	=	multiq_destroy,

	.change		=	multiq_tune,

	.dump		=	multiq_dump,

	.owner		=	THIS_MODULE,

};



static int __init multiq_module_init(void)

{

	return register_qdisc(&multiq_qdisc_ops);

}



static void __exit multiq_module_exit(void)

{

	unregister_qdisc(&multiq_qdisc_ops);

}



module_init(multiq_module_init)

module_exit(multiq_module_exit)



MODULE_LICENSE("GPL");

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