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Message-ID: <1505797616.29839.40.camel@edumazet-glaptop3.roam.corp.google.com>
Date: Mon, 18 Sep 2017 22:06:56 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: David Miller <davem@...emloft.net>
Cc: netdev <netdev@...r.kernel.org>
Subject: [PATCH net-next] net: sk_buff rbnode reorg
From: Eric Dumazet <edumazet@...gle.com>
skb->rbnode shares space with skb->next, skb->prev and skb->tstamp
Current uses (TCP receive ofo queue and netem) need to save/restore
tstamp.
Since we might use an RB tree for TCP retransmit queue at some point
to speedup SACK processing with large rtx queues, this patch exchanges
skb->dev and skb->tstamp.
This saves some overhead in both TCP and netem.
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
include/linux/skbuff.h | 16 ++++++++--------
include/net/tcp.h | 5 -----
net/ipv4/tcp_input.c | 27 +++++----------------------
net/sched/sch_netem.c | 7 ++++---
4 files changed, 17 insertions(+), 38 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 72299ef00061db1ce70d34b96ae1639ecde08837..492828801acba42ac6bccb287d3cc5080039135c 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -661,8 +661,12 @@ struct sk_buff {
struct sk_buff *prev;
union {
- ktime_t tstamp;
- u64 skb_mstamp;
+ struct net_device *dev;
+ /* Some protocols might use this space to store information,
+ * while device pointer would be NULL.
+ * UDP receive path is one user.
+ */
+ unsigned long dev_scratch;
};
};
struct rb_node rbnode; /* used in netem & tcp stack */
@@ -670,12 +674,8 @@ struct sk_buff {
struct sock *sk;
union {
- struct net_device *dev;
- /* Some protocols might use this space to store information,
- * while device pointer would be NULL.
- * UDP receive path is one user.
- */
- unsigned long dev_scratch;
+ ktime_t tstamp;
+ u64 skb_mstamp;
};
/*
* This is the control buffer. It is free to use for every
diff --git a/include/net/tcp.h b/include/net/tcp.h
index b510f284427aabc1f508d24d29d0f812e5e0aa61..6ecc01aa667b26a3e2270a3566b2076bfebd8605 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -797,11 +797,6 @@ struct tcp_skb_cb {
u16 tcp_gso_segs;
u16 tcp_gso_size;
};
-
- /* Used to stash the receive timestamp while this skb is in the
- * out of order queue, as skb->tstamp is overwritten by the
- * rbnode.
- */
ktime_t swtstamp;
};
__u8 tcp_flags; /* TCP header flags. (tcp[13]) */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index bddf724f5c02abe1d11110cffe2517f6376e440d..db9bb46b5776f9ee332298c0e95afb0a5966b938 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4266,11 +4266,6 @@ static void tcp_sack_remove(struct tcp_sock *tp)
tp->rx_opt.num_sacks = num_sacks;
}
-enum tcp_queue {
- OOO_QUEUE,
- RCV_QUEUE,
-};
-
/**
* tcp_try_coalesce - try to merge skb to prior one
* @sk: socket
@@ -4286,7 +4281,6 @@ enum tcp_queue {
* Returns true if caller should free @from instead of queueing it
*/
static bool tcp_try_coalesce(struct sock *sk,
- enum tcp_queue dest,
struct sk_buff *to,
struct sk_buff *from,
bool *fragstolen)
@@ -4311,10 +4305,7 @@ static bool tcp_try_coalesce(struct sock *sk,
if (TCP_SKB_CB(from)->has_rxtstamp) {
TCP_SKB_CB(to)->has_rxtstamp = true;
- if (dest == OOO_QUEUE)
- TCP_SKB_CB(to)->swtstamp = TCP_SKB_CB(from)->swtstamp;
- else
- to->tstamp = from->tstamp;
+ to->tstamp = from->tstamp;
}
return true;
@@ -4351,9 +4342,6 @@ static void tcp_ofo_queue(struct sock *sk)
}
p = rb_next(p);
rb_erase(&skb->rbnode, &tp->out_of_order_queue);
- /* Replace tstamp which was stomped by rbnode */
- if (TCP_SKB_CB(skb)->has_rxtstamp)
- skb->tstamp = TCP_SKB_CB(skb)->swtstamp;
if (unlikely(!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))) {
SOCK_DEBUG(sk, "ofo packet was already received\n");
@@ -4365,8 +4353,7 @@ static void tcp_ofo_queue(struct sock *sk)
TCP_SKB_CB(skb)->end_seq);
tail = skb_peek_tail(&sk->sk_receive_queue);
- eaten = tail && tcp_try_coalesce(sk, RCV_QUEUE,
- tail, skb, &fragstolen);
+ eaten = tail && tcp_try_coalesce(sk, tail, skb, &fragstolen);
tcp_rcv_nxt_update(tp, TCP_SKB_CB(skb)->end_seq);
fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
if (!eaten)
@@ -4420,10 +4407,6 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
return;
}
- /* Stash tstamp to avoid being stomped on by rbnode */
- if (TCP_SKB_CB(skb)->has_rxtstamp)
- TCP_SKB_CB(skb)->swtstamp = skb->tstamp;
-
/* Disable header prediction. */
tp->pred_flags = 0;
inet_csk_schedule_ack(sk);
@@ -4451,7 +4434,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
/* In the typical case, we are adding an skb to the end of the list.
* Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
*/
- if (tcp_try_coalesce(sk, OOO_QUEUE, tp->ooo_last_skb,
+ if (tcp_try_coalesce(sk, tp->ooo_last_skb,
skb, &fragstolen)) {
coalesce_done:
tcp_grow_window(sk, skb);
@@ -4502,7 +4485,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
__kfree_skb(skb1);
goto merge_right;
}
- } else if (tcp_try_coalesce(sk, OOO_QUEUE, skb1,
+ } else if (tcp_try_coalesce(sk, skb1,
skb, &fragstolen)) {
goto coalesce_done;
}
@@ -4554,7 +4537,7 @@ static int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, int
__skb_pull(skb, hdrlen);
eaten = (tail &&
- tcp_try_coalesce(sk, RCV_QUEUE, tail,
+ tcp_try_coalesce(sk, tail,
skb, fragstolen)) ? 1 : 0;
tcp_rcv_nxt_update(tcp_sk(sk), TCP_SKB_CB(skb)->end_seq);
if (!eaten) {
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index b1266e75ca43cf5a66b951ecabccfc5b24069444..063a4bdb9ee6f26b01387959e8f6ccd15ec16191 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -146,7 +146,6 @@ struct netem_sched_data {
*/
struct netem_skb_cb {
psched_time_t time_to_send;
- ktime_t tstamp_save;
};
@@ -561,7 +560,6 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
}
cb->time_to_send = now + delay;
- cb->tstamp_save = skb->tstamp;
++q->counter;
tfifo_enqueue(skb, sch);
} else {
@@ -629,7 +627,10 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
qdisc_qstats_backlog_dec(sch, skb);
skb->next = NULL;
skb->prev = NULL;
- skb->tstamp = netem_skb_cb(skb)->tstamp_save;
+ /* skb->dev shares skb->rbnode area,
+ * we need to restore its value.
+ */
+ skb->dev = qdisc_dev(sch);
#ifdef CONFIG_NET_CLS_ACT
/*
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