Commit 6da7c8fc authored by stephen hemminger's avatar stephen hemminger Committed by David S. Miller
Browse files

qdisc: allow setting default queuing discipline 



By default, the pfifo_fast queue discipline has been used by default
for all devices. But we have better choices now.

This patch allow setting the default queueing discipline with sysctl.
This allows easy use of better queueing disciplines on all devices
without having to use tc qdisc scripts. It is intended to allow
an easy path for distributions to make fq_codel or sfq the default
qdisc.

This patch also makes pfifo_fast more of a first class qdisc, since
it is now possible to manually override the default and explicitly
use pfifo_fast. The behavior for systems who do not use the sysctl
is unchanged, they still get pfifo_fast

Also removes leftover random # in sysctl net core.

Signed-off-by: default avatarStephen Hemminger <stephen@networkplumber.org>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7d7628f3

Documentation/sysctl/net.txt

+13 −0
Original line number Diff line number Diff line
@@ -50,6 +50,19 @@ The maximum number of packets that kernel can handle on a NAPI interrupt, 
it's a Per-CPU variable.

Default: 64



default_qdisc

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



The default queuing discipline to use for network devices. This allows

overriding the default queue discipline of pfifo_fast with an

alternative. Since the default queuing discipline is created with the

no additional parameters so is best suited to queuing disciplines that

work well without configuration like stochastic fair queue (sfq),

CoDel (codel) or fair queue CoDel (fq_codel). Don't use queuing disciplines

like Hierarchical Token Bucket or Deficit Round Robin which require setting

up classes and bandwidths.

Default: pfifo_fast



busy_read

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

Low latency busy poll timeout for socket reads. (needs CONFIG_NET_RX_BUSY_POLL)

include/net/pkt_sched.h

+3 −0
Original line number Diff line number Diff line
@@ -85,6 +85,9 @@ struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops, 


int register_qdisc(struct Qdisc_ops *qops);

int unregister_qdisc(struct Qdisc_ops *qops);

void qdisc_get_default(char *id, size_t len);

int qdisc_set_default(const char *id);



void qdisc_list_del(struct Qdisc *q);

struct Qdisc *qdisc_lookup(struct net_device *dev, u32 handle);

struct Qdisc *qdisc_lookup_class(struct net_device *dev, u32 handle);

include/net/sch_generic.h

+1 −0
Original line number Diff line number Diff line
@@ -316,6 +316,7 @@ extern struct Qdisc noop_qdisc; 
extern struct Qdisc_ops noop_qdisc_ops;

extern struct Qdisc_ops pfifo_fast_ops;

extern struct Qdisc_ops mq_qdisc_ops;

extern const struct Qdisc_ops *default_qdisc_ops;



struct Qdisc_class_common {

	u32			classid;

net/core/sysctl_net_core.c

+29 −1
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <net/sock.h>

#include <net/net_ratelimit.h>

#include <net/busy_poll.h>

#include <net/pkt_sched.h>



static int zero = 0;

static int one = 1;
@@ -193,6 +194,26 @@ static int flow_limit_table_len_sysctl(struct ctl_table *table, int write, 
}

#endif /* CONFIG_NET_FLOW_LIMIT */



#ifdef CONFIG_NET_SCHED

static int set_default_qdisc(struct ctl_table *table, int write,

			     void __user *buffer, size_t *lenp, loff_t *ppos)

{

	char id[IFNAMSIZ];

	struct ctl_table tbl = {

		.data = id,

		.maxlen = IFNAMSIZ,

	};

	int ret;



	qdisc_get_default(id, IFNAMSIZ);



	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);

	if (write && ret == 0)

		ret = qdisc_set_default(id);

	return ret;

}

#endif



static struct ctl_table net_core_table[] = {

#ifdef CONFIG_NET

	{
@@ -315,7 +336,14 @@ static struct ctl_table net_core_table[] = { 
		.mode		= 0644,

		.proc_handler	= proc_dointvec

	},

#

#endif

#ifdef CONFIG_NET_SCHED

	{

		.procname	= "default_qdisc",

		.mode		= 0644,

		.maxlen		= IFNAMSIZ,

		.proc_handler	= set_default_qdisc

	},

#endif

#endif /* CONFIG_NET */

	{

net/sched/sch_api.c

+58 −0
Original line number Diff line number Diff line
@@ -131,6 +131,11 @@ static DEFINE_RWLOCK(qdisc_mod_lock); 
 ************************************************/





/* Qdisc to use by default */



const struct Qdisc_ops *default_qdisc_ops = &pfifo_fast_ops;

EXPORT_SYMBOL(default_qdisc_ops);



/* The list of all installed queueing disciplines. */



static struct Qdisc_ops *qdisc_base;
@@ -200,6 +205,58 @@ int unregister_qdisc(struct Qdisc_ops *qops) 
}

EXPORT_SYMBOL(unregister_qdisc);



/* Get default qdisc if not otherwise specified */

void qdisc_get_default(char *name, size_t len)

{

	read_lock(&qdisc_mod_lock);

	strlcpy(name, default_qdisc_ops->id, len);

	read_unlock(&qdisc_mod_lock);

}



static struct Qdisc_ops *qdisc_lookup_default(const char *name)

{

	struct Qdisc_ops *q = NULL;



	for (q = qdisc_base; q; q = q->next) {

		if (!strcmp(name, q->id)) {

			if (!try_module_get(q->owner))

				q = NULL;

			break;

		}

	}



	return q;

}



/* Set new default qdisc to use */

int qdisc_set_default(const char *name)

{

	const struct Qdisc_ops *ops;



	if (!capable(CAP_NET_ADMIN))

		return -EPERM;



	write_lock(&qdisc_mod_lock);

	ops = qdisc_lookup_default(name);

	if (!ops) {

		/* Not found, drop lock and try to load module */

		write_unlock(&qdisc_mod_lock);

		request_module("sch_%s", name);

		write_lock(&qdisc_mod_lock);



		ops = qdisc_lookup_default(name);

	}



	if (ops) {

		/* Set new default */

		module_put(default_qdisc_ops->owner);

		default_qdisc_ops = ops;

	}

	write_unlock(&qdisc_mod_lock);



	return ops ? 0 : -ENOENT;

}



/* We know handle. Find qdisc among all qdisc's attached to device

   (root qdisc, all its children, children of children etc.)

 */
@@ -1854,6 +1911,7 @@ static int __init pktsched_init(void) 
		return err;

	}



	register_qdisc(&pfifo_fast_ops);

	register_qdisc(&pfifo_qdisc_ops);

	register_qdisc(&bfifo_qdisc_ops);

	register_qdisc(&pfifo_head_drop_qdisc_ops);

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