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netem: use rb tree to implement the time queue
Following typical setup to implement a ~100 ms RTT and big amount of reorders has very poor performance because netem implements the time queue using a linked list. ----------------------------------------------------------- ETH=eth0 IFB=ifb0 modprobe ifb ip link set dev $IFB up tc qdisc add dev $ETH ingress 2>/dev/null tc filter add dev $ETH parent ffff: \ protocol ip u32 match u32 0 0 flowid 1:1 action mirred egress \ redirect dev $IFB ethtool -K $ETH gro off tso off gso off tc qdisc add dev $IFB root netem delay 50ms 10ms limit 100000 tc qd add dev $ETH root netem delay 50ms limit 100000 --------------------------------------------------------- Switch netem time queue to a rb tree, so this kind of setup can work at high speed. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Stephen Hemminger <stephen@networkplumber.org> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
David S. Miller
parent
d0b5e51629
commit
aec0a40a6f
@ -23,6 +23,7 @@
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#include <linux/vmalloc.h>
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#include <linux/rtnetlink.h>
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#include <linux/reciprocal_div.h>
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#include <linux/rbtree.h>
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#include <net/netlink.h>
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#include <net/pkt_sched.h>
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@ -68,7 +69,8 @@
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*/
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struct netem_sched_data {
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/* internal t(ime)fifo qdisc uses sch->q and sch->limit */
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/* internal t(ime)fifo qdisc uses t_root and sch->limit */
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struct rb_root t_root;
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/* optional qdisc for classful handling (NULL at netem init) */
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struct Qdisc *qdisc;
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@ -128,10 +130,35 @@ struct netem_sched_data {
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*/
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struct netem_skb_cb {
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psched_time_t time_to_send;
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ktime_t tstamp_save;
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};
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/* Because space in skb->cb[] is tight, netem overloads skb->next/prev/tstamp
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* to hold a rb_node structure.
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*
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* If struct sk_buff layout is changed, the following checks will complain.
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*/
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static struct rb_node *netem_rb_node(struct sk_buff *skb)
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{
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BUILD_BUG_ON(offsetof(struct sk_buff, next) != 0);
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BUILD_BUG_ON(offsetof(struct sk_buff, prev) !=
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offsetof(struct sk_buff, next) + sizeof(skb->next));
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BUILD_BUG_ON(offsetof(struct sk_buff, tstamp) !=
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offsetof(struct sk_buff, prev) + sizeof(skb->prev));
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BUILD_BUG_ON(sizeof(struct rb_node) > sizeof(skb->next) +
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sizeof(skb->prev) +
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sizeof(skb->tstamp));
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return (struct rb_node *)&skb->next;
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}
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static struct sk_buff *netem_rb_to_skb(struct rb_node *rb)
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{
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return (struct sk_buff *)rb;
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}
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static inline struct netem_skb_cb *netem_skb_cb(struct sk_buff *skb)
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{
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/* we assume we can use skb next/prev/tstamp as storage for rb_node */
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qdisc_cb_private_validate(skb, sizeof(struct netem_skb_cb));
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return (struct netem_skb_cb *)qdisc_skb_cb(skb)->data;
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}
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@ -333,20 +360,23 @@ static psched_time_t packet_len_2_sched_time(unsigned int len, struct netem_sche
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static void tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
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{
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struct sk_buff_head *list = &sch->q;
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struct netem_sched_data *q = qdisc_priv(sch);
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psched_time_t tnext = netem_skb_cb(nskb)->time_to_send;
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struct sk_buff *skb = skb_peek_tail(list);
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struct rb_node **p = &q->t_root.rb_node, *parent = NULL;
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/* Optimize for add at tail */
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if (likely(!skb || tnext >= netem_skb_cb(skb)->time_to_send))
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return __skb_queue_tail(list, nskb);
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while (*p) {
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struct sk_buff *skb;
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skb_queue_reverse_walk(list, skb) {
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parent = *p;
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skb = netem_rb_to_skb(parent);
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if (tnext >= netem_skb_cb(skb)->time_to_send)
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break;
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p = &parent->rb_right;
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else
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p = &parent->rb_left;
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}
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__skb_queue_after(list, skb, nskb);
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rb_link_node(netem_rb_node(nskb), parent, p);
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rb_insert_color(netem_rb_node(nskb), &q->t_root);
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sch->q.qlen++;
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}
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/*
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@ -436,23 +466,28 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
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now = psched_get_time();
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if (q->rate) {
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struct sk_buff_head *list = &sch->q;
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struct sk_buff *last;
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if (!skb_queue_empty(list)) {
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if (!skb_queue_empty(&sch->q))
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last = skb_peek_tail(&sch->q);
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else
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last = netem_rb_to_skb(rb_last(&q->t_root));
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if (last) {
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/*
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* Last packet in queue is reference point (now),
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* calculate this time bonus and subtract
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* from delay.
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*/
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delay -= netem_skb_cb(skb_peek_tail(list))->time_to_send - now;
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delay -= netem_skb_cb(last)->time_to_send - now;
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delay = max_t(psched_tdiff_t, 0, delay);
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now = netem_skb_cb(skb_peek_tail(list))->time_to_send;
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now = netem_skb_cb(last)->time_to_send;
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}
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delay += packet_len_2_sched_time(skb->len, q);
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}
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cb->time_to_send = now + delay;
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cb->tstamp_save = skb->tstamp;
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++q->counter;
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tfifo_enqueue(skb, sch);
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} else {
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@ -476,6 +511,21 @@ static unsigned int netem_drop(struct Qdisc *sch)
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unsigned int len;
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len = qdisc_queue_drop(sch);
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if (!len) {
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struct rb_node *p = rb_first(&q->t_root);
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if (p) {
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struct sk_buff *skb = netem_rb_to_skb(p);
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rb_erase(p, &q->t_root);
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sch->q.qlen--;
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skb->next = NULL;
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skb->prev = NULL;
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len = qdisc_pkt_len(skb);
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kfree_skb(skb);
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}
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}
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if (!len && q->qdisc && q->qdisc->ops->drop)
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len = q->qdisc->ops->drop(q->qdisc);
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if (len)
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@ -488,19 +538,32 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
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{
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struct netem_sched_data *q = qdisc_priv(sch);
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struct sk_buff *skb;
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struct rb_node *p;
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if (qdisc_is_throttled(sch))
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return NULL;
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tfifo_dequeue:
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skb = qdisc_peek_head(sch);
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skb = __skb_dequeue(&sch->q);
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if (skb) {
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const struct netem_skb_cb *cb = netem_skb_cb(skb);
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deliver:
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sch->qstats.backlog -= qdisc_pkt_len(skb);
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qdisc_unthrottled(sch);
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qdisc_bstats_update(sch, skb);
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return skb;
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}
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p = rb_first(&q->t_root);
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if (p) {
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skb = netem_rb_to_skb(p);
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/* if more time remaining? */
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if (cb->time_to_send <= psched_get_time()) {
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__skb_unlink(skb, &sch->q);
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sch->qstats.backlog -= qdisc_pkt_len(skb);
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if (netem_skb_cb(skb)->time_to_send <= psched_get_time()) {
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rb_erase(p, &q->t_root);
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sch->q.qlen--;
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skb->next = NULL;
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skb->prev = NULL;
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skb->tstamp = netem_skb_cb(skb)->tstamp_save;
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#ifdef CONFIG_NET_CLS_ACT
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/*
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@ -522,10 +585,7 @@ tfifo_dequeue:
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}
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goto tfifo_dequeue;
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}
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deliver:
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qdisc_unthrottled(sch);
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qdisc_bstats_update(sch, skb);
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return skb;
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goto deliver;
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}
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if (q->qdisc) {
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@ -533,7 +593,8 @@ deliver:
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if (skb)
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goto deliver;
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}
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qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
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qdisc_watchdog_schedule(&q->watchdog,
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netem_skb_cb(skb)->time_to_send);
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}
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if (q->qdisc) {
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