From: David Miller <davem@davemloft.net>
To: ncardwell@google.com
Cc: brakmo@fb.com, ycheng@google.com, daniel@iogearbox.net,
netdev@vger.kernel.org, Kernel-team@fb.com, ast@fb.com,
eric.dumazet@gmail.com
Subject: Re: [PATCH net-next] tcp: ack immediately when a cwr packet arrives
Date: Wed, 25 Jul 2018 16:21:38 -0700 (PDT) [thread overview]
Message-ID: <20180725.162138.394671961252485113.davem@davemloft.net> (raw)
In-Reply-To: <CADVnQy=RAP6QYdCpkXNKXGQgS0TTWof=VazUeN=jHqtcTZxFig@mail.gmail.com>
From: Neal Cardwell <ncardwell@google.com>
Date: Tue, 24 Jul 2018 21:57:27 -0400
> On Tue, Jul 24, 2018 at 1:42 PM Lawrence Brakmo <brakmo@fb.com> wrote:
>>
>> Note that without this fix the 99% latencies when doing 10KB RPCs
>> in a congested network using DCTCP are 40ms vs. 190us with the patch.
>> Also note that these 40ms high tail latencies started after commit
>> 3759824da87b30ce7a35b4873b62b0ba38905ef5 in Jul 2015,
>> which triggered the bugs/features we are fixing/adding. I agree it is a
>> debatable whether it is a bug fix or a feature improvement and I am
>> fine either way.
>
> Good point. The fact that this greatly mitigates a regression in DCTCP
> performance resulting from 3759824da87b30ce7a35b4873b62b0ba38905ef5
> ("tcp: PRR uses CRB mode by default and SS mode conditionally") IMHO
> seems to be a good argument for putting this patch ("tcp: ack
> immediately when a cwr packet arrives") in the "net" branch and stable
> releases.
Thus, applied to 'net' and queued up for -stable.
prev parent reply other threads:[~2018-07-26 0:35 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-24 0:49 [PATCH net-next] tcp: ack immediately when a cwr packet arrives Lawrence Brakmo
2018-07-24 2:15 ` Neal Cardwell
2018-07-24 2:23 ` Daniel Borkmann
2018-07-24 17:06 ` Yuchung Cheng
2018-07-24 17:12 ` Neal Cardwell
2018-07-24 17:26 ` Eric Dumazet
2018-07-24 17:42 ` Lawrence Brakmo
2018-07-25 1:57 ` Neal Cardwell
2018-07-25 23:21 ` David Miller [this message]
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