netdev - Re: [PATCH] tcp: provide tx timestamps for partial writes

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Date:   Tue, 3 Jan 2017 10:22:20 -0500
From:   Soheil Hassas Yeganeh <soheil@...gle.com>
To:     David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>
Cc:     Willem de Bruijn <willemb@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Martin KaFai Lau <kafai@...com>
Subject: Re: [PATCH] tcp: provide tx timestamps for partial writes

On Mon, Jan 2, 2017 at 3:23 PM, Soheil Hassas Yeganeh <soheil@...gle.com> wrote:
> On Mon, Jan 2, 2017 at 3:20 PM, Soheil Hassas Yeganeh
> <soheil.kdev@...il.com> wrote:
>> From: Soheil Hassas Yeganeh <soheil@...gle.com>
>>
>> For TCP sockets, tx timestamps are only captured when the user data
>> is successfully and fully written to the socket. In many cases,
>> however, TCP writes can be partial for which no timestamp is
>> collected.
>>
>> Collect timestamps when the user data is partially copied into
>> the socket.
>>
>> Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
>> Cc: Willem de Bruijn <willemb@...gle.com>
>> Cc: Yuchung Cheng <ycheng@...gle.com>
>> Cc: Eric Dumazet <edumazet@...gle.com>
>> Cc: Neal Cardwell <ncardwell@...gle.com>
>> Cc: Martin KaFai Lau <kafai@...com>
>> ---
>>  net/ipv4/tcp.c | 8 ++++++--
>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
>> index 2e3807d..c207b16 100644
>> --- a/net/ipv4/tcp.c
>> +++ b/net/ipv4/tcp.c
>> @@ -992,8 +992,10 @@ static ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
>>         return copied;
>>
>>  do_error:
>> -       if (copied)
>> +       if (copied) {
>> +               tcp_tx_timestamp(sk, sk->sk_tsflags, tcp_write_queue_tail(sk));
>>                 goto out;
>> +       }
>>  out_err:
>>         /* make sure we wake any epoll edge trigger waiter */
>>         if (unlikely(skb_queue_len(&sk->sk_write_queue) == 0 &&
>> @@ -1329,8 +1331,10 @@ int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
>>         }
>>
>>  do_error:
>> -       if (copied + copied_syn)
>> +       if (copied + copied_syn) {
>> +               tcp_tx_timestamp(sk, sk->sk_tsflags, tcp_write_queue_tail(sk));

Thanks to Willem for noting that this should be sockc.tsflags and not
sk->sk_tsflags. I'll send V2 to fix.

Soheil

>>                 goto out;
>> +       }
>>  out_err:
>>         err = sk_stream_error(sk, flags, err);
>>         /* make sure we wake any epoll edge trigger waiter */
>> --
>> 2.8.0.rc3.226.g39d4020
>>
>
> I'm sorry for the incomplete annotation. This is for [net-next].
>
> Thanks,
> Soheil