Subject: [net-next PATCH 3/3] qdisc: sysctl to adjust bulk dequeue limit

From: Jesper Dangaard Brouer <[email-masked]>
Date: Tue, 02 Sep 2014 16:36:09 +0200

Allow userspace to adjust how many packet the qdisc is allowed to
bulk dequeue.

Signed-off-by: Jesper Dangaard Brouer <[email-masked]>

---
Question should we allow this to be adjusted?

 include/net/sch_generic.h  |    2 ++
 net/core/sysctl_net_core.c |    9 +++++++++
 net/sched/sch_generic.c    |    4 +++-
 3 files changed, 14 insertions(+), 1 deletions(-)

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index a3cfb8e..b0ac7b5 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -14,6 +14,8 @@ struct qdisc_walker;
 struct tcf_walker;
 struct module;
 
+extern int qdisc_bulk_dequeue_limit;
+
 struct qdisc_rate_table {
 	struct tc_ratespec rate;
 	u32		data[256];
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index cf9cd13..5505841 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -361,6 +361,15 @@ static struct ctl_table net_core_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec
 	},
+	{
+		.procname	= "qdisc_bulk_dequeue_limit",
+		.data		= &qdisc_bulk_dequeue_limit,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.extra1		= &zero,
+		.extra2		= &ushort_max,
+		.proc_handler	= proc_dointvec_minmax
+	},
 	{ }
 };
 
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 30814ef..9cb08c0 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -34,6 +34,8 @@
 const struct Qdisc_ops *default_qdisc_ops = &pfifo_fast_ops;
 EXPORT_SYMBOL(default_qdisc_ops);
 
+int qdisc_bulk_dequeue_limit __read_mostly = 7;
+
 /* Main transmission queue. */
 
 /* Modifications to data participating in scheduling must be protected with
@@ -81,7 +83,7 @@ static inline struct sk_buff *dequeue_skb(struct Qdisc *q)
 			/* bulk dequeue */
 			if (skb && !skb->next && (q->flags & TCQ_F_ONETXQUEUE)) {
 				struct sk_buff *new, *head = skb;
-				int limit = 7;
+				int limit = qdisc_bulk_dequeue_limit;
 
 				do {
 					new = q->dequeue(q);