netdev - Re: [PATCH net 2/3] tcp: enable xmit timer fix by having TLP use time when RTO should fire

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Message-ID: <CADVnQy=A27-P7bystCPhu_Tk6cwLOL4Kqz2FSSg55nzNc3cixA@mail.gmail.com>
Date:   Tue, 1 Aug 2017 10:35:58 -0400
From:   Neal Cardwell <ncardwell@...gle.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        Yuchung Cheng <ycheng@...gle.com>,
        Nandita Dukkipati <nanditad@...gle.com>
Subject: Re: [PATCH net 2/3] tcp: enable xmit timer fix by having TLP use time
 when RTO should fire

On Tue, Aug 1, 2017 at 3:22 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Mon, 2017-07-31 at 22:58 -0400, Neal Cardwell wrote:
>> @@ -2418,13 +2418,9 @@ bool tcp_schedule_loss_probe(struct sock *sk)
>>       timeout = max_t(u32, timeout, msecs_to_jiffies(10));
>>
>>       /* If RTO is shorter, just schedule TLP in its place. */
>
> I have hard time to read this comment.
>
> We are here trying to arm a timer based on TLP.
>
> If RTO is shorter, we'll arm the timer based on RTO instead of TLP.
>
> Is "If RTO is shorter, just schedule TLP in its place." really correct ?
>
> I suggest we reword the comment or simply get rid of it now the code is
> more obvious.

OK, how about:

  /* If the RTO formula yields an earlier time, then use that time. */

We can also add a reference to the RACK/TLP Internet Draft at the top
of tcp_schedule_loss_probe().

Whatever wording we decide on, I am happy to send a patch for net-next
once this fix is merged into net-next.

neal