[PATCH net-next] net: sched: use pfifo_fast for non real queues

[Eric Dumazet]

Some devices declare a high number of TX queues, then set a much
lower real_num_tx_queues

This cause setups using fq_codel, sfq or fq as the default qdisc to consume
more memory than really needed.

Signed-off-by: Eric Dumazet <eduma...@google.com>
---
 include/net/sch_generic.h | 6 ++++++
 net/sched/sch_generic.c   | 1 +
 net/sched/sch_mq.c        | 2 +-
 net/sched/sch_mqprio.c    | 3 ++-
 4 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index e5bba897d206..46e55f0202a6 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -345,6 +345,12 @@ extern struct Qdisc_ops pfifo_fast_ops;
 extern struct Qdisc_ops mq_qdisc_ops;
 extern struct Qdisc_ops noqueue_qdisc_ops;
 extern const struct Qdisc_ops *default_qdisc_ops;
+static inline const struct Qdisc_ops *
+get_default_qdisc_ops(const struct net_device *dev, int ntx)
+{
+       return ntx < dev->real_num_tx_queues ?
+                       default_qdisc_ops : &pfifo_fast_ops;
+}
 
 struct Qdisc_class_common {
        u32                     classid;
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 16bc83b2842a..f18c35024207 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -567,6 +567,7 @@ struct Qdisc_ops pfifo_fast_ops __read_mostly = {
        .dump           =       pfifo_fast_dump,
        .owner          =       THIS_MODULE,
 };
+EXPORT_SYMBOL(pfifo_fast_ops);
 
 static struct lock_class_key qdisc_tx_busylock;
 
diff --git a/net/sched/sch_mq.c b/net/sched/sch_mq.c
index 3e82f047caaf..56a77b878eb3 100644
--- a/net/sched/sch_mq.c
+++ b/net/sched/sch_mq.c
@@ -57,7 +57,7 @@ static int mq_init(struct Qdisc *sch, struct nlattr *opt)
 
        for (ntx = 0; ntx < dev->num_tx_queues; ntx++) {
                dev_queue = netdev_get_tx_queue(dev, ntx);
-               qdisc = qdisc_create_dflt(dev_queue, default_qdisc_ops,
+               qdisc = qdisc_create_dflt(dev_queue, get_default_qdisc_ops(dev, 
ntx),
                                          TC_H_MAKE(TC_H_MAJ(sch->handle),
                                                    TC_H_MIN(ntx + 1)));
                if (qdisc == NULL)
diff --git a/net/sched/sch_mqprio.c b/net/sched/sch_mqprio.c
index 02ffb3fbbc20..b8002ce3d010 100644
--- a/net/sched/sch_mqprio.c
+++ b/net/sched/sch_mqprio.c
@@ -125,7 +125,8 @@ static int mqprio_init(struct Qdisc *sch, struct nlattr 
*opt)
 
        for (i = 0; i < dev->num_tx_queues; i++) {
                dev_queue = netdev_get_tx_queue(dev, i);
-               qdisc = qdisc_create_dflt(dev_queue, default_qdisc_ops,
+               qdisc = qdisc_create_dflt(dev_queue,
+                                         get_default_qdisc_ops(dev, i),
                                          TC_H_MAKE(TC_H_MAJ(sch->handle),
                                                    TC_H_MIN(i + 1)));
                if (qdisc == NULL) {
-- 
2.7.0.rc3.207.g0ac5344