From: "Tilmans, Olivier (Nokia - BE/Antwerp)" <olivier.tilmans@nokia-bell-labs.com>
To: Lawrence Brakmo <brakmo@fb.com>, David Miller <davem@davemloft.net>
Cc: "De Schepper,
Koen (Nokia - BE/Antwerp)"
<koen.de_schepper@nokia-bell-labs.com>,
"research@bobbriscoe.net" <research@bobbriscoe.net>,
"fw@strlen.de" <fw@strlen.de>,
"borkmann@iogearbox.net" <borkmann@iogearbox.net>,
"ycheng@google.com" <ycheng@google.com>,
"ncardwell@google.com" <ncardwell@google.com>,
"edumazet@google.com" <edumazet@google.com>,
"agshew@gmail.com" <agshew@gmail.com>,
"glenn.judd@morganstanley.com" <glenn.judd@morganstanley.com>,
"kuznet@ms2.inr.ac.ru" <kuznet@ms2.inr.ac.ru>,
"yoshfuji@linux-ipv6.org" <yoshfuji@linux-ipv6.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH net-next v2] tcp: Ensure DCTCP reacts to losses
Date: Thu, 4 Apr 2019 18:39:31 +0000 [thread overview]
Message-ID: <AM6PR07MB4821BB64AF86A1A650C95000E0500@AM6PR07MB4821.eurprd07.prod.outlook.com> (raw)
In-Reply-To: <532BB0D8-95C8-4A4D-A73D-3B563909780F@fb.com>
> DCTCP is meant to be used in environments where the switches/routers do
> ECN marking, so it is not surprising that it performs badly when used in
> environments where it was not meant to be used. Has anyone measured the
> effect of this changed when DCTCP is used in environments where all the
> switches/routers do ECN marking? My concern is that we could end up
> hurting performance when DCTCP is used how it was meant to be used in
> order to protect incorrect uses of DCTCP.
The results reported are indeed from a non-optimal setting, and mostly to
show that it was ignoring losses. In practice, we only use DCTCP on
ECN-enabled AQMs, and rarely see the loss reaction (e.g., a burst of new flows
IW that congest the ToR switch, in which case I'd argue the behavior is
beneficial). I cannot estimate the impact on FB's workloads though.
I had originally put a module parameter to make this loss reaction behavior
optional, mostly to enable people to check first whether it was safe to use
with their configuration. In hindsight, I should have waited a bit more
before submitting the v2 with its removal as requested.
Olivier
next prev parent reply other threads:[~2019-04-04 18:39 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-04 12:24 [PATCH net-next v2] tcp: Ensure DCTCP reacts to losses Tilmans, Olivier (Nokia - BE/Antwerp)
2019-04-04 13:17 ` Florian Westphal
2019-04-04 13:48 ` Neal Cardwell
2019-04-04 13:55 ` Neal Cardwell
2019-04-04 13:59 ` Daniel Borkmann
2019-04-04 17:52 ` David Miller
2019-04-04 18:10 ` Lawrence Brakmo
2019-04-04 18:39 ` Tilmans, Olivier (Nokia - BE/Antwerp) [this message]
2019-04-04 18:55 ` Lawrence Brakmo
2019-04-05 9:23 ` Eric Dumazet
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