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Date: Sun, 18 Sep 2016 00:57:34 +0200
From: Florian Westphal <fw@...len.de>
To: <netdev@...r.kernel.org>
Cc: Florian Westphal <fw@...len.de>
Subject: [PATCH net-next 5/5] sched: add and use qdisc_skb_head helpers
This change replaces sk_buff_head struct in Qdiscs with new qdisc_skb_head.
Its similar to the skb_buff_head api, but does not use skb->prev pointers.
Qdiscs will commonly enqueue at the tail of a list and dequeue at head.
While skb_buff_head works fine for this, enqueue/dequeue needs to also
adjust the prev pointer of next element.
The ->prev pointer is not required for qdiscs so we can just leave
it undefined and avoid one cacheline write access for en/dequeue.
Suggested-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: Florian Westphal <fw@...len.de>
---
include/net/sch_generic.h | 63 ++++++++++++++++++++++++++++++++++++++---------
net/sched/sch_generic.c | 21 ++++++++--------
net/sched/sch_htb.c | 24 +++++++++++++++---
net/sched/sch_netem.c | 14 +++++++++--
4 files changed, 94 insertions(+), 28 deletions(-)
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 0741ed4..e6aa0a2 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -36,6 +36,14 @@ struct qdisc_size_table {
u16 data[];
};
+/* similar to sk_buff_head, but skb->prev pointer is undefined. */
+struct qdisc_skb_head {
+ struct sk_buff *head;
+ struct sk_buff *tail;
+ __u32 qlen;
+ spinlock_t lock;
+};
+
struct Qdisc {
int (*enqueue)(struct sk_buff *skb,
struct Qdisc *sch,
@@ -76,7 +84,7 @@ struct Qdisc {
* For performance sake on SMP, we put highly modified fields at the end
*/
struct sk_buff *gso_skb ____cacheline_aligned_in_smp;
- struct sk_buff_head q;
+ struct qdisc_skb_head q;
struct gnet_stats_basic_packed bstats;
seqcount_t running;
struct gnet_stats_queue qstats;
@@ -600,10 +608,27 @@ static inline void qdisc_qstats_overlimit(struct Qdisc *sch)
sch->qstats.overlimits++;
}
+static inline void qdisc_skb_head_init(struct qdisc_skb_head *qh)
+{
+ qh->head = NULL;
+ qh->tail = NULL;
+ qh->qlen = 0;
+}
+
static inline int __qdisc_enqueue_tail(struct sk_buff *skb, struct Qdisc *sch,
- struct sk_buff_head *list)
+ struct qdisc_skb_head *qh)
{
- __skb_queue_tail(list, skb);
+ struct sk_buff *last = qh->tail;
+
+ if (last) {
+ skb->next = NULL;
+ last->next = skb;
+ qh->tail = skb;
+ } else {
+ qh->tail = skb;
+ qh->head = skb;
+ }
+ qh->qlen++;
qdisc_qstats_backlog_inc(sch, skb);
return NET_XMIT_SUCCESS;
@@ -614,9 +639,17 @@ static inline int qdisc_enqueue_tail(struct sk_buff *skb, struct Qdisc *sch)
return __qdisc_enqueue_tail(skb, sch, &sch->q);
}
-static inline struct sk_buff *__qdisc_dequeue_head(struct sk_buff_head *list)
+static inline struct sk_buff *__qdisc_dequeue_head(struct qdisc_skb_head *qh)
{
- struct sk_buff *skb = __skb_dequeue(list);
+ struct sk_buff *skb = qh->head;
+
+ if (likely(skb != NULL)) {
+ qh->head = skb->next;
+ qh->qlen--;
+ if (qh->head == NULL)
+ qh->tail = NULL;
+ skb->next = NULL;
+ }
return skb;
}
@@ -643,10 +676,10 @@ static inline void __qdisc_drop(struct sk_buff *skb, struct sk_buff **to_free)
}
static inline unsigned int __qdisc_queue_drop_head(struct Qdisc *sch,
- struct sk_buff_head *list,
+ struct qdisc_skb_head *qh,
struct sk_buff **to_free)
{
- struct sk_buff *skb = __skb_dequeue(list);
+ struct sk_buff *skb = __qdisc_dequeue_head(qh);
if (likely(skb != NULL)) {
unsigned int len = qdisc_pkt_len(skb);
@@ -667,7 +700,9 @@ static inline unsigned int qdisc_queue_drop_head(struct Qdisc *sch,
static inline struct sk_buff *qdisc_peek_head(struct Qdisc *sch)
{
- return skb_peek(&sch->q);
+ const struct qdisc_skb_head *qh = &sch->q;
+
+ return qh->head;
}
/* generic pseudo peek method for non-work-conserving qdisc */
@@ -702,15 +737,19 @@ static inline struct sk_buff *qdisc_dequeue_peeked(struct Qdisc *sch)
return skb;
}
-static inline void __qdisc_reset_queue(struct sk_buff_head *list)
+static inline void __qdisc_reset_queue(struct qdisc_skb_head *qh)
{
/*
* We do not know the backlog in bytes of this list, it
* is up to the caller to correct it
*/
- if (!skb_queue_empty(list)) {
- rtnl_kfree_skbs(list->next, list->prev);
- __skb_queue_head_init(list);
+ ASSERT_RTNL();
+ if (qh->qlen) {
+ rtnl_kfree_skbs(qh->head, qh->tail);
+
+ qh->head = NULL;
+ qh->tail = NULL;
+ qh->qlen = 0;
}
}
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 73877d9..6cfb6e9 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -466,7 +466,7 @@ static const u8 prio2band[TC_PRIO_MAX + 1] = {
*/
struct pfifo_fast_priv {
u32 bitmap;
- struct sk_buff_head q[PFIFO_FAST_BANDS];
+ struct qdisc_skb_head q[PFIFO_FAST_BANDS];
};
/*
@@ -477,7 +477,7 @@ struct pfifo_fast_priv {
*/
static const int bitmap2band[] = {-1, 0, 1, 0, 2, 0, 1, 0};
-static inline struct sk_buff_head *band2list(struct pfifo_fast_priv *priv,
+static inline struct qdisc_skb_head *band2list(struct pfifo_fast_priv *priv,
int band)
{
return priv->q + band;
@@ -489,7 +489,7 @@ static int pfifo_fast_enqueue(struct sk_buff *skb, struct Qdisc *qdisc,
if (qdisc->q.qlen < qdisc_dev(qdisc)->tx_queue_len) {
int band = prio2band[skb->priority & TC_PRIO_MAX];
struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
- struct sk_buff_head *list = band2list(priv, band);
+ struct qdisc_skb_head *list = band2list(priv, band);
priv->bitmap |= (1 << band);
qdisc->q.qlen++;
@@ -505,8 +505,8 @@ static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc)
int band = bitmap2band[priv->bitmap];
if (likely(band >= 0)) {
- struct sk_buff_head *list = band2list(priv, band);
- struct sk_buff *skb = __qdisc_dequeue_head(list);
+ struct qdisc_skb_head *qh = band2list(priv, band);
+ struct sk_buff *skb = __qdisc_dequeue_head(qh);
if (likely(skb != NULL)) {
qdisc_qstats_backlog_dec(qdisc, skb);
@@ -514,7 +514,7 @@ static struct sk_buff *pfifo_fast_dequeue(struct Qdisc *qdisc)
}
qdisc->q.qlen--;
- if (skb_queue_empty(list))
+ if (qh->qlen == 0)
priv->bitmap &= ~(1 << band);
return skb;
@@ -529,9 +529,9 @@ static struct sk_buff *pfifo_fast_peek(struct Qdisc *qdisc)
int band = bitmap2band[priv->bitmap];
if (band >= 0) {
- struct sk_buff_head *list = band2list(priv, band);
+ struct qdisc_skb_head *qh = band2list(priv, band);
- return skb_peek(list);
+ return qh->head;
}
return NULL;
@@ -569,7 +569,7 @@ static int pfifo_fast_init(struct Qdisc *qdisc, struct nlattr *opt)
struct pfifo_fast_priv *priv = qdisc_priv(qdisc);
for (prio = 0; prio < PFIFO_FAST_BANDS; prio++)
- __skb_queue_head_init(band2list(priv, prio));
+ qdisc_skb_head_init(band2list(priv, prio));
/* Can by-pass the queue discipline */
qdisc->flags |= TCQ_F_CAN_BYPASS;
@@ -617,7 +617,8 @@ struct Qdisc *qdisc_alloc(struct netdev_queue *dev_queue,
sch = (struct Qdisc *) QDISC_ALIGN((unsigned long) p);
sch->padded = (char *) sch - (char *) p;
}
- skb_queue_head_init(&sch->q);
+ qdisc_skb_head_init(&sch->q);
+ spin_lock_init(&sch->q.lock);
spin_lock_init(&sch->busylock);
lockdep_set_class(&sch->busylock,
diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 53dbfa1..c798d0d 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -162,7 +162,7 @@ struct htb_sched {
struct work_struct work;
/* non shaped skbs; let them go directly thru */
- struct sk_buff_head direct_queue;
+ struct qdisc_skb_head direct_queue;
long direct_pkts;
struct qdisc_watchdog watchdog;
@@ -570,6 +570,22 @@ static inline void htb_deactivate(struct htb_sched *q, struct htb_class *cl)
list_del_init(&cl->un.leaf.drop_list);
}
+static void htb_enqueue_tail(struct sk_buff *skb, struct Qdisc *sch,
+ struct qdisc_skb_head *qh)
+{
+ struct sk_buff *last = qh->tail;
+
+ if (last) {
+ skb->next = NULL;
+ last->next = skb;
+ qh->tail = skb;
+ } else {
+ qh->tail = skb;
+ qh->head = skb;
+ }
+ qh->qlen++;
+}
+
static int htb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct sk_buff **to_free)
{
@@ -580,7 +596,7 @@ static int htb_enqueue(struct sk_buff *skb, struct Qdisc *sch,
if (cl == HTB_DIRECT) {
/* enqueue to helper queue */
if (q->direct_queue.qlen < q->direct_qlen) {
- __skb_queue_tail(&q->direct_queue, skb);
+ htb_enqueue_tail(skb, sch, &q->direct_queue);
q->direct_pkts++;
} else {
return qdisc_drop(skb, sch, to_free);
@@ -888,7 +904,7 @@ static struct sk_buff *htb_dequeue(struct Qdisc *sch)
unsigned long start_at;
/* try to dequeue direct packets as high prio (!) to minimize cpu work */
- skb = __skb_dequeue(&q->direct_queue);
+ skb = __qdisc_dequeue_head(&q->direct_queue);
if (skb != NULL) {
ok:
qdisc_bstats_update(sch, skb);
@@ -1019,7 +1035,7 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt)
qdisc_watchdog_init(&q->watchdog, sch);
INIT_WORK(&q->work, htb_work_func);
- __skb_queue_head_init(&q->direct_queue);
+ qdisc_skb_head_init(&q->direct_queue);
if (tb[TCA_HTB_DIRECT_QLEN])
q->direct_qlen = nla_get_u32(tb[TCA_HTB_DIRECT_QLEN]);
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 0a964b3..9f7b380 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -413,6 +413,16 @@ static struct sk_buff *netem_segment(struct sk_buff *skb, struct Qdisc *sch,
return segs;
}
+static void netem_enqueue_skb_head(struct qdisc_skb_head *qh, struct sk_buff *skb)
+{
+ skb->next = qh->head;
+
+ if (!qh->head)
+ qh->tail = skb;
+ qh->head = skb;
+ qh->qlen++;
+}
+
/*
* Insert one skb into qdisc.
* Note: parent depends on return value to account for queue length.
@@ -523,7 +533,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
struct sk_buff *last;
if (sch->q.qlen)
- last = skb_peek_tail(&sch->q);
+ last = sch->q.tail;
else
last = netem_rb_to_skb(rb_last(&q->t_root));
if (last) {
@@ -552,7 +562,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
cb->time_to_send = psched_get_time();
q->counter = 0;
- __skb_queue_head(&sch->q, skb);
+ netem_enqueue_skb_head(&sch->q, skb);
sch->qstats.requeues++;
}
--
2.7.3
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