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Message-ID: <1335989484.9611.11.camel@joe2Laptop>
Date: Wed, 02 May 2012 13:11:24 -0700
From: Joe Perches <joe@...ches.com>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: David Miller <davem@...emloft.net>,
Alexander Duyck <alexander.duyck@...il.com>,
Alexander Duyck <alexander.h.duyck@...el.com>,
netdev <netdev@...r.kernel.org>,
Neal Cardwell <ncardwell@...gle.com>,
Tom Herbert <therbert@...gle.com>,
Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
Michael Chan <mchan@...adcom.com>,
Matt Carlson <mcarlson@...adcom.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
Ben Hutchings <bhutchings@...arflare.com>,
Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>,
Maciej Żenczykowski <maze@...gle.com>
Subject: Re: [PATCH net-next] net: implement tcp coalescing in
tcp_queue_rcv()
On Wed, 2012-05-02 at 21:58 +0200, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
>
> Extend tcp coalescing implementing it from tcp_queue_rcv(), the main
> receiver function when application is not blocked in recvmsg().
>
> Function tcp_queue_rcv() is moved a bit to allow its call from
> tcp_data_queue()
>
> This gives good results especially if GRO could not kick, and if skb
> head is a fragment.
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Alexander Duyck <alexander.h.duyck@...el.com>
> Cc: Neal Cardwell <ncardwell@...gle.com>
> Cc: Tom Herbert <therbert@...gle.com>
> ---
> To be applied after "[PATCH v2 net-next] net: take care of cloned skbs
> in tcp_try_coalesce()"
>
> include/net/tcp.h | 3 ++-
> net/ipv4/tcp.c | 10 +++++-----
> net/ipv4/tcp_input.c | 40 +++++++++++++++++++++-------------------
> 3 files changed, 28 insertions(+), 25 deletions(-)
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 0fb84de..a9d2fb8 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -438,7 +438,8 @@ extern int tcp_disconnect(struct sock *sk, int flags);
>
> void tcp_connect_init(struct sock *sk);
> void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
> -void tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, int hdrlen);
> +int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb,
> + int hdrlen, bool *fragstolen);
>
> /* From syncookies.c */
> extern __u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> index 9670af3..bd5deff 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -980,8 +980,8 @@ static inline int select_size(const struct sock *sk, bool sg)
> static int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
> {
> struct sk_buff *skb;
> - struct tcp_skb_cb *cb;
> struct tcphdr *th;
> + bool fragstolen;
It might be useful to comment that this is/can be initialized to
false in tcp_try_coalesce via tcp_recv_queue.
> skb = alloc_skb(size + sizeof(*th), sk->sk_allocation);
> if (!skb)
> @@ -994,14 +994,14 @@ static int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
> if (memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size))
> goto err_free;
>
> - cb = TCP_SKB_CB(skb);
> -
> TCP_SKB_CB(skb)->seq = tcp_sk(sk)->rcv_nxt;
> TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + size;
> TCP_SKB_CB(skb)->ack_seq = tcp_sk(sk)->snd_una - 1;
>
> - tcp_queue_rcv(sk, skb, sizeof(*th));
> -
> + if (tcp_queue_rcv(sk, skb, sizeof(*th), &fragstolen)) {
> + WARN_ON_ONCE(fragstolen); /* should not happen */
Otherwise this looks like a possibly uninitialized test
of fragstolen. Maybe there's a path where tail is null
in tcp_recv_queue and it's an uninitialized test anyway.
> + __kfree_skb(skb);
> + }
> return size;
>
> err_free:
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index f891a5e..2233468 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -4662,6 +4662,22 @@ end:
> skb_set_owner_r(skb, sk);
> }
>
> +int tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, int hdrlen,
> + bool *fragstolen)
> +{
> + int eaten;
> + struct sk_buff *tail = skb_peek_tail(&sk->sk_receive_queue);
> +
> + __skb_pull(skb, hdrlen);
> + eaten = (tail &&
> + tcp_try_coalesce(sk, tail, skb, fragstolen)) ? 1 : 0;
> + tcp_sk(sk)->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
> + if (!eaten) {
> + __skb_queue_tail(&sk->sk_receive_queue, skb);
> + skb_set_owner_r(skb, sk);
> + }
> + return eaten;
> +}
--
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