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Date: Sat, 4 May 2019 16:48:53 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Willem de Bruijn <willemb@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 1/2] net_sched: sch_fq: do not assume EDT packets are ordered
TCP stack makes sure packets for a given flow are monotically
increasing, but we want to allow UDP packets to use EDT as
well, so that QUIC servers can use in-kernel pacing.
This patch adds a per-flow rb-tree on which packets might
be stored. We still try to use the linear list for the
typical cases where packets are queued with monotically
increasing skb->tstamp, since queue/dequeue packets on
a standard list is O(1).
Note that the ability to store packets in arbitrary EDT
order will allow us to implement later a per TCP socket
mechanism adding delays (with jitter eventually) and reorders,
to implement convenient network emulators.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
net/sched/sch_fq.c | 95 ++++++++++++++++++++++++++++++++++++++++------
1 file changed, 83 insertions(+), 12 deletions(-)
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index d107c74767cd1d3258b7f038c0c3176db589a51f..ee138365ec45ee01cb10f149ae5b1d7635fa1185 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -54,10 +54,23 @@
#include <net/tcp_states.h>
#include <net/tcp.h>
+struct fq_skb_cb {
+ u64 time_to_send;
+};
+
+static inline struct fq_skb_cb *fq_skb_cb(struct sk_buff *skb)
+{
+ qdisc_cb_private_validate(skb, sizeof(struct fq_skb_cb));
+ return (struct fq_skb_cb *)qdisc_skb_cb(skb)->data;
+}
+
/*
- * Per flow structure, dynamically allocated
+ * Per flow structure, dynamically allocated.
+ * If packets have monotically increasing time_to_send, they are placed in O(1)
+ * in linear list (head,tail), otherwise are placed in a rbtree (t_root).
*/
struct fq_flow {
+ struct rb_root t_root;
struct sk_buff *head; /* list of skbs for this flow : first skb */
union {
struct sk_buff *tail; /* last skb in the list */
@@ -298,6 +311,8 @@ static struct fq_flow *fq_classify(struct sk_buff *skb, struct fq_sched_data *q)
q->stat_allocation_errors++;
return &q->internal;
}
+ /* f->t_root is already zeroed after kmem_cache_zalloc() */
+
fq_flow_set_detached(f);
f->sk = sk;
if (skb->sk)
@@ -312,14 +327,40 @@ static struct fq_flow *fq_classify(struct sk_buff *skb, struct fq_sched_data *q)
return f;
}
+static struct sk_buff *fq_peek(struct fq_flow *flow)
+{
+ struct sk_buff *skb = skb_rb_first(&flow->t_root);
+ struct sk_buff *head = flow->head;
+
+ if (!skb)
+ return head;
+
+ if (!head)
+ return skb;
+
+ if (fq_skb_cb(skb)->time_to_send < fq_skb_cb(head)->time_to_send)
+ return skb;
+ return head;
+}
+
+static void fq_erase_head(struct Qdisc *sch, struct fq_flow *flow,
+ struct sk_buff *skb)
+{
+ if (skb == flow->head) {
+ flow->head = skb->next;
+ } else {
+ rb_erase(&skb->rbnode, &flow->t_root);
+ skb->dev = qdisc_dev(sch);
+ }
+}
/* remove one skb from head of flow queue */
static struct sk_buff *fq_dequeue_head(struct Qdisc *sch, struct fq_flow *flow)
{
- struct sk_buff *skb = flow->head;
+ struct sk_buff *skb = fq_peek(flow);
if (skb) {
- flow->head = skb->next;
+ fq_erase_head(sch, flow, skb);
skb_mark_not_on_list(skb);
flow->qlen--;
qdisc_qstats_backlog_dec(sch, skb);
@@ -330,15 +371,36 @@ static struct sk_buff *fq_dequeue_head(struct Qdisc *sch, struct fq_flow *flow)
static void flow_queue_add(struct fq_flow *flow, struct sk_buff *skb)
{
- struct sk_buff *head = flow->head;
+ struct rb_node **p, *parent;
+ struct sk_buff *head, *aux;
- skb->next = NULL;
- if (!head)
- flow->head = skb;
- else
- flow->tail->next = skb;
+ fq_skb_cb(skb)->time_to_send = skb->tstamp ?: ktime_get_ns();
- flow->tail = skb;
+ head = flow->head;
+ if (!head ||
+ fq_skb_cb(skb)->time_to_send >= fq_skb_cb(flow->tail)->time_to_send) {
+ if (!head)
+ flow->head = skb;
+ else
+ flow->tail->next = skb;
+ flow->tail = skb;
+ skb->next = NULL;
+ return;
+ }
+
+ p = &flow->t_root.rb_node;
+ parent = NULL;
+
+ while (*p) {
+ parent = *p;
+ aux = rb_to_skb(parent);
+ if (fq_skb_cb(skb)->time_to_send >= fq_skb_cb(aux)->time_to_send)
+ p = &parent->rb_right;
+ else
+ p = &parent->rb_left;
+ }
+ rb_link_node(&skb->rbnode, parent, p);
+ rb_insert_color(&skb->rbnode, &flow->t_root);
}
static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
@@ -450,9 +512,9 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch)
goto begin;
}
- skb = f->head;
+ skb = fq_peek(f);
if (skb) {
- u64 time_next_packet = max_t(u64, ktime_to_ns(skb->tstamp),
+ u64 time_next_packet = max_t(u64, fq_skb_cb(skb)->time_to_send,
f->time_next_packet);
if (now < time_next_packet) {
@@ -533,6 +595,15 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch)
static void fq_flow_purge(struct fq_flow *flow)
{
+ struct rb_node *p = rb_first(&flow->t_root);
+
+ while (p) {
+ struct sk_buff *skb = rb_to_skb(p);
+
+ p = rb_next(p);
+ rb_erase(&skb->rbnode, &flow->t_root);
+ rtnl_kfree_skbs(skb, skb);
+ }
rtnl_kfree_skbs(flow->head, flow->tail);
flow->head = NULL;
flow->qlen = 0;
--
2.21.0.1020.gf2820cf01a-goog
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