Merge branch 'net-sched-bulk-dequeue'

Eric Dumazet says:

====================
net_sched: bulk dequeue and deferred drops

First patch adds an additional parameter to ->enqueue() qdisc method
so that drops can be done outside of critical section
(after locks are released).

Then fq_codel can have a small optimization to reduce number of cache
lines misses during a drop event
(possibly accumulating hundreds of packets to be freed).

A small htb change exports the backlog in class dumps.

Final patch adds bulk dequeue to qdiscs that were lacking this feature.

This series brings a nice qdisc performance increase (more than 80 %
in some cases).
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/codel_qdisc.h

@@ -52,6 +52,7 @@
 /* Qdiscs using codel plugin must use codel_skb_cb in their own cb[] */
 struct codel_skb_cb {
 	codel_time_t enqueue_time;
+	unsigned int mem_usage;
 };
 
 static struct codel_skb_cb *get_codel_cb(const struct sk_buff *skb)

include/net/sch_generic.h

@@ -37,8 +37,10 @@ struct qdisc_size_table {
 };
 
 struct Qdisc {
-	int 			(*enqueue)(struct sk_buff *skb, struct Qdisc *dev);
-	struct sk_buff *	(*dequeue)(struct Qdisc *dev);
+	int 			(*enqueue)(struct sk_buff *skb,
+					   struct Qdisc *sch,
+					   struct sk_buff **to_free);
+	struct sk_buff *	(*dequeue)(struct Qdisc *sch);
 	unsigned int		flags;
 #define TCQ_F_BUILTIN		1
 #define TCQ_F_INGRESS		2
@@ -73,13 +75,14 @@ struct Qdisc {
 	/*
 	 * For performance sake on SMP, we put highly modified fields at the end
 	 */
-	struct Qdisc		*next_sched ____cacheline_aligned_in_smp;
-	struct sk_buff		*gso_skb;
-	unsigned long		state;
+	struct sk_buff		*gso_skb ____cacheline_aligned_in_smp;
 	struct sk_buff_head	q;
 	struct gnet_stats_basic_packed bstats;
 	seqcount_t		running;
 	struct gnet_stats_queue	qstats;
+	unsigned long		state;
+	struct Qdisc            *next_sched;
+	struct sk_buff		*skb_bad_txq;
 	struct rcu_head		rcu_head;
 	int			padded;
 	atomic_t		refcnt;
@@ -160,7 +163,9 @@ struct Qdisc_ops {
 	char			id[IFNAMSIZ];
 	int			priv_size;
 
-	int 			(*enqueue)(struct sk_buff *, struct Qdisc *);
+	int 			(*enqueue)(struct sk_buff *skb,
+					   struct Qdisc *sch,
+					   struct sk_buff **to_free);
 	struct sk_buff *	(*dequeue)(struct Qdisc *);
 	struct sk_buff *	(*peek)(struct Qdisc *);
 
@@ -498,10 +503,11 @@ static inline void qdisc_calculate_pkt_len(struct sk_buff *skb,
 #endif
 }
 
-static inline int qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+static inline int qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+				struct sk_buff **to_free)
 {
 	qdisc_calculate_pkt_len(skb, sch);
-	return sch->enqueue(skb, sch);
+	return sch->enqueue(skb, sch, to_free);
 }
 
 static inline bool qdisc_is_percpu_stats(const struct Qdisc *q)
@@ -626,24 +632,36 @@ static inline struct sk_buff *qdisc_dequeue_head(struct Qdisc *sch)
 	return __qdisc_dequeue_head(sch, &sch->q);
 }
 
+/* Instead of calling kfree_skb() while root qdisc lock is held,
+ * queue the skb for future freeing at end of __dev_xmit_skb()
+ */
+static inline void __qdisc_drop(struct sk_buff *skb, struct sk_buff **to_free)
+{
+	skb->next = *to_free;
+	*to_free = skb;
+}
+
 static inline unsigned int __qdisc_queue_drop_head(struct Qdisc *sch,
-					      struct sk_buff_head *list)
+						   struct sk_buff_head *list,
+						   struct sk_buff **to_free)
 {
 	struct sk_buff *skb = __skb_dequeue(list);
 
 	if (likely(skb != NULL)) {
 		unsigned int len = qdisc_pkt_len(skb);
+
 		qdisc_qstats_backlog_dec(sch, skb);
-		kfree_skb(skb);
+		__qdisc_drop(skb, to_free);
 		return len;
 	}
 
 	return 0;
 }
 
-static inline unsigned int qdisc_queue_drop_head(struct Qdisc *sch)
+static inline unsigned int qdisc_queue_drop_head(struct Qdisc *sch,
+						 struct sk_buff **to_free)
 {
-	return __qdisc_queue_drop_head(sch, &sch->q);
+	return __qdisc_queue_drop_head(sch, &sch->q, to_free);
 }
 
 static inline struct sk_buff *qdisc_peek_head(struct Qdisc *sch)
@@ -724,9 +742,11 @@ static inline void rtnl_qdisc_drop(struct sk_buff *skb, struct Qdisc *sch)
 	qdisc_qstats_drop(sch);
 }
 
-static inline int qdisc_drop(struct sk_buff *skb, struct Qdisc *sch)
+
+static inline int qdisc_drop(struct sk_buff *skb, struct Qdisc *sch,
+			     struct sk_buff **to_free)
 {
-	kfree_skb(skb);
+	__qdisc_drop(skb, to_free);
 	qdisc_qstats_drop(sch);
 
 	return NET_XMIT_DROP;

net/core/dev.c

@@ -3070,6 +3070,7 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
 				 struct netdev_queue *txq)
 {
 	spinlock_t *root_lock = qdisc_lock(q);
+	struct sk_buff *to_free = NULL;
 	bool contended;
 	int rc;
 
@@ -3086,7 +3087,7 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
 
 	spin_lock(root_lock);
 	if (unlikely(test_bit(__QDISC_STATE_DEACTIVATED, &q->state))) {
-		kfree_skb(skb);
+		__qdisc_drop(skb, &to_free);
 		rc = NET_XMIT_DROP;
 	} else if ((q->flags & TCQ_F_CAN_BYPASS) && !qdisc_qlen(q) &&
 		   qdisc_run_begin(q)) {
@@ -3109,7 +3110,7 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
 
 		rc = NET_XMIT_SUCCESS;
 	} else {
-		rc = q->enqueue(skb, q) & NET_XMIT_MASK;
+		rc = q->enqueue(skb, q, &to_free) & NET_XMIT_MASK;
 		if (qdisc_run_begin(q)) {
 			if (unlikely(contended)) {
 				spin_unlock(&q->busylock);
@@ -3119,6 +3120,8 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
 		}
 	}
 	spin_unlock(root_lock);
+	if (unlikely(to_free))
+		kfree_skb_list(to_free);
 	if (unlikely(contended))
 		spin_unlock(&q->busylock);
 	return rc;

net/sched/sch_atm.c

@@ -357,7 +357,8 @@ static struct tcf_proto __rcu **atm_tc_find_tcf(struct Qdisc *sch,
 
 /* --------------------------- Qdisc operations ---------------------------- */
 
-static int atm_tc_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+static int atm_tc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+			  struct sk_buff **to_free)
 {
 	struct atm_qdisc_data *p = qdisc_priv(sch);
 	struct atm_flow_data *flow;
@@ -398,10 +399,10 @@ static int atm_tc_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 		switch (result) {
 		case TC_ACT_QUEUED:
 		case TC_ACT_STOLEN:
-			kfree_skb(skb);
+			__qdisc_drop(skb, to_free);
 			return NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
 		case TC_ACT_SHOT:
-			kfree_skb(skb);
+			__qdisc_drop(skb, to_free);
 			goto drop;
 		case TC_ACT_RECLASSIFY:
 			if (flow->excess)
@@ -413,7 +414,7 @@ static int atm_tc_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 #endif
 	}
 
-	ret = qdisc_enqueue(skb, flow->q);
+	ret = qdisc_enqueue(skb, flow->q, to_free);
 	if (ret != NET_XMIT_SUCCESS) {
 drop: __maybe_unused
 		if (net_xmit_drop_count(ret)) {

net/sched/sch_blackhole.c

@@ -17,9 +17,10 @@
 #include <linux/skbuff.h>
 #include <net/pkt_sched.h>
 
-static int blackhole_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+static int blackhole_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+			     struct sk_buff **to_free)
 {
-	qdisc_drop(skb, sch);
+	qdisc_drop(skb, sch, to_free);
 	return NET_XMIT_SUCCESS;
 }
 

net/sched/sch_cbq.c

@@ -358,7 +358,8 @@ cbq_mark_toplevel(struct cbq_sched_data *q, struct cbq_class *cl)
 }
 
 static int
-cbq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+cbq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+	    struct sk_buff **to_free)
 {
 	struct cbq_sched_data *q = qdisc_priv(sch);
 	int uninitialized_var(ret);
@@ -370,11 +371,11 @@ cbq_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 	if (cl == NULL) {
 		if (ret & __NET_XMIT_BYPASS)
 			qdisc_qstats_drop(sch);
-		kfree_skb(skb);
+		__qdisc_drop(skb, to_free);
 		return ret;
 	}
 
-	ret = qdisc_enqueue(skb, cl->q);
+	ret = qdisc_enqueue(skb, cl->q, to_free);
 	if (ret == NET_XMIT_SUCCESS) {
 		sch->q.qlen++;
 		cbq_mark_toplevel(q, cl);

net/sched/sch_choke.c

@@ -115,7 +115,8 @@ static void choke_zap_tail_holes(struct choke_sched_data *q)
 }
 
 /* Drop packet from queue array by creating a "hole" */
-static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx)
+static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx,
+			      struct sk_buff **to_free)
 {
 	struct choke_sched_data *q = qdisc_priv(sch);
 	struct sk_buff *skb = q->tab[idx];
@@ -129,7 +130,7 @@ static void choke_drop_by_idx(struct Qdisc *sch, unsigned int idx)
 
 	qdisc_qstats_backlog_dec(sch, skb);
 	qdisc_tree_reduce_backlog(sch, 1, qdisc_pkt_len(skb));
-	qdisc_drop(skb, sch);
+	qdisc_drop(skb, sch, to_free);
 	--sch->q.qlen;
 }
 
@@ -261,7 +262,8 @@ static bool choke_match_random(const struct choke_sched_data *q,
 	return choke_match_flow(oskb, nskb);
 }
 
-static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+			 struct sk_buff **to_free)
 {
 	int ret = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
 	struct choke_sched_data *q = qdisc_priv(sch);
@@ -288,7 +290,7 @@ static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 		/* Draw a packet at random from queue and compare flow */
 		if (choke_match_random(q, skb, &idx)) {
 			q->stats.matched++;
-			choke_drop_by_idx(sch, idx);
+			choke_drop_by_idx(sch, idx, to_free);
 			goto congestion_drop;
 		}
 
@@ -331,16 +333,16 @@ static int choke_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 	}
 
 	q->stats.pdrop++;
-	return qdisc_drop(skb, sch);
+	return qdisc_drop(skb, sch, to_free);
 
 congestion_drop:
-	qdisc_drop(skb, sch);
+	qdisc_drop(skb, sch, to_free);
 	return NET_XMIT_CN;
 
 other_drop:
 	if (ret & __NET_XMIT_BYPASS)
 		qdisc_qstats_drop(sch);
-	kfree_skb(skb);
+	__qdisc_drop(skb, to_free);
 	return ret;
 }
 

net/sched/sch_codel.c

@@ -82,7 +82,8 @@ static void drop_func(struct sk_buff *skb, void *ctx)
 {
 	struct Qdisc *sch = ctx;
 
-	qdisc_drop(skb, sch);
+	kfree_skb(skb);
+	qdisc_qstats_drop(sch);
 }
 
 static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
@@ -107,7 +108,8 @@ static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
 	return skb;
 }
 
-static int codel_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+static int codel_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+			       struct sk_buff **to_free)
 {
 	struct codel_sched_data *q;
 
@@ -117,7 +119,7 @@ static int codel_qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 	}
 	q = qdisc_priv(sch);
 	q->drop_overlimit++;
-	return qdisc_drop(skb, sch);
+	return qdisc_drop(skb, sch, to_free);
 }
 
 static const struct nla_policy codel_policy[TCA_CODEL_MAX + 1] = {

net/sched/sch_drr.c

@@ -350,7 +350,8 @@ static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch,
 	return NULL;
 }
 
-static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+		       struct sk_buff **to_free)
 {
 	struct drr_sched *q = qdisc_priv(sch);
 	struct drr_class *cl;
@@ -360,11 +361,11 @@ static int drr_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 	if (cl == NULL) {
 		if (err & __NET_XMIT_BYPASS)
 			qdisc_qstats_drop(sch);
-		kfree_skb(skb);
+		__qdisc_drop(skb, to_free);
 		return err;
 	}
 
-	err = qdisc_enqueue(skb, cl->qdisc);
+	err = qdisc_enqueue(skb, cl->qdisc, to_free);
 	if (unlikely(err != NET_XMIT_SUCCESS)) {
 		if (net_xmit_drop_count(err)) {
 			cl->qstats.drops++;

net/sched/sch_dsmark.c

@@ -191,7 +191,8 @@ static inline struct tcf_proto __rcu **dsmark_find_tcf(struct Qdisc *sch,
 
 /* --------------------------- Qdisc operations ---------------------------- */
 
-static int dsmark_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+static int dsmark_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+			  struct sk_buff **to_free)
 {
 	struct dsmark_qdisc_data *p = qdisc_priv(sch);
 	int err;
@@ -234,7 +235,7 @@ static int dsmark_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 #ifdef CONFIG_NET_CLS_ACT
 		case TC_ACT_QUEUED:
 		case TC_ACT_STOLEN:
-			kfree_skb(skb);
+			__qdisc_drop(skb, to_free);
 			return NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
 
 		case TC_ACT_SHOT:
@@ -251,7 +252,7 @@ static int dsmark_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 		}
 	}
 
-	err = qdisc_enqueue(skb, p->q);
+	err = qdisc_enqueue(skb, p->q, to_free);
 	if (err != NET_XMIT_SUCCESS) {
 		if (net_xmit_drop_count(err))
 			qdisc_qstats_drop(sch);
@@ -264,7 +265,7 @@ static int dsmark_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 	return NET_XMIT_SUCCESS;
 
 drop:
-	qdisc_drop(skb, sch);
+	qdisc_drop(skb, sch, to_free);
 	return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
 }