From: Neal Cardwell <ncardwell@google.com>
To: Lisong Xu <xu@unl.edu>
Cc: Yuchung Cheng <ycheng@google.com>, Wei Sun <unlcsewsun@gmail.com>,
netdev <netdev@vger.kernel.org>
Subject: Re: A buggy behavior for Linux TCP Reno and HTCP
Date: Fri, 21 Jul 2017 16:49:14 -0400 [thread overview]
Message-ID: <CADVnQym8-0-jEaBYpHAodg5ODH6GUCS_tMQbKyWdPKLpxq7ATA@mail.gmail.com> (raw)
In-Reply-To: <CADVnQynG0MZcuAPpZ+hiK-9Ounx8JKPWxvb1n3t-OyyC7=es_Q@mail.gmail.com>
On Fri, Jul 21, 2017 at 4:27 PM, Lisong Xu <xu@unl.edu> wrote:
>
> Hi Yuchung,
>
> This test scenario is only one example to trigger this bug. In general, as long as cwnd <4, the undo function has this bug.
Yes, personally I agree that this seems like an issue that is general
enough to be worth fixing. In the sense that, if cwnd <4, then we may
well be very congested. So we don't want to get hit by this bug
wherein an undo of a loss recovery can cause cwnd to suddenly jump
(from 1, 2, or 3) up to 4.
Seems like any of the several CCs that use tcp_reno_undo_cwnd() have this bug.
I guess in my mind the only question is whether we want to add a
tcp_foo_undo_cwnd() and ca->loss_cwnd to every CC module to handle
this issue (i.e. make every CC module handle it the way CUBIC does),
or (my preference) just add a tp->loss_cwnd field so we can use shared
code in tcp_reno_undo_cwnd() to get this right across all CC modules.
neal
next prev parent reply other threads:[~2017-07-21 20:49 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-18 21:36 A buggy behavior for Linux TCP Reno and HTCP Wei Sun
2017-07-19 19:31 ` Yuchung Cheng
2017-07-20 21:28 ` Wei Sun
2017-07-21 17:59 ` Yuchung Cheng
2017-07-21 20:26 ` Lisong Xu
2017-07-21 20:27 ` Lisong Xu
[not found] ` <CADVnQynG0MZcuAPpZ+hiK-9Ounx8JKPWxvb1n3t-OyyC7=es_Q@mail.gmail.com>
2017-07-21 20:49 ` Neal Cardwell [this message]
2017-07-21 21:16 ` Yuchung Cheng
2017-07-24 2:36 ` Neal Cardwell
2017-07-24 2:37 ` Neal Cardwell
2017-07-24 18:17 ` Yuchung Cheng
2017-07-24 18:29 ` Neal Cardwell
2017-07-24 23:41 ` Yuchung Cheng
2017-07-25 4:19 ` Stephen Hemminger
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