diff options
| author | Eric Dumazet | 2016-05-02 10:56:27 -0700 |
|---|---|---|
| committer | David S. Miller | 2016-05-03 16:02:36 -0400 |
| commit | 1d2077ac0165c0d173a2255e37cf4dc5033d92c7 (patch) | |
| tree | fc18bebb7e5ffe2109fd61c56230c5f47d5f313b /net | |
| parent | e34b1638d02bef8c3278af30ee73077c5babc082 (diff) | |
net: add __sock_wfree() helper
Hosts sending lot of ACK packets exhibit high sock_wfree() cost
because of cache line miss to test SOCK_USE_WRITE_QUEUE
We could move this flag close to sk_wmem_alloc but it is better
to perform the atomic_sub_and_test() on a clean cache line,
as it avoid one extra bus transaction.
skb_orphan_partial() can also have a fast track for packets that either
are TCP acks, or already went through another skb_orphan_partial()
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/core/sock.c | 24 | ||||
| -rw-r--r-- | net/ipv4/tcp_output.c | 2 |
2 files changed, 25 insertions, 1 deletions
diff --git a/net/core/sock.c b/net/core/sock.c index f615e9391170..08bf97eceeb3 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1655,6 +1655,17 @@ void sock_wfree(struct sk_buff *skb) } EXPORT_SYMBOL(sock_wfree); +/* This variant of sock_wfree() is used by TCP, + * since it sets SOCK_USE_WRITE_QUEUE. + */ +void __sock_wfree(struct sk_buff *skb) +{ + struct sock *sk = skb->sk; + + if (atomic_sub_and_test(skb->truesize, &sk->sk_wmem_alloc)) + __sk_free(sk); +} + void skb_set_owner_w(struct sk_buff *skb, struct sock *sk) { skb_orphan(skb); @@ -1677,8 +1688,21 @@ void skb_set_owner_w(struct sk_buff *skb, struct sock *sk) } EXPORT_SYMBOL(skb_set_owner_w); +/* This helper is used by netem, as it can hold packets in its + * delay queue. We want to allow the owner socket to send more + * packets, as if they were already TX completed by a typical driver. + * But we also want to keep skb->sk set because some packet schedulers + * rely on it (sch_fq for example). So we set skb->truesize to a small + * amount (1) and decrease sk_wmem_alloc accordingly. + */ void skb_orphan_partial(struct sk_buff *skb) { + /* If this skb is a TCP pure ACK or already went here, + * we have nothing to do. 2 is already a very small truesize. + */ + if (skb->truesize <= 2) + return; + /* TCP stack sets skb->ooo_okay based on sk_wmem_alloc, * so we do not completely orphan skb, but transfert all * accounted bytes but one, to avoid unexpected reorders. diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 25d527922b18..8daefd8b1b49 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -949,7 +949,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, skb_orphan(skb); skb->sk = sk; - skb->destructor = skb_is_tcp_pure_ack(skb) ? sock_wfree : tcp_wfree; + skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree; skb_set_hash_from_sk(skb, sk); atomic_add(skb->truesize, &sk->sk_wmem_alloc); |