bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Ivan Babrou <ivan@cloudflare.com>
To: Dave Taht <dave.taht@gmail.com>
Cc: bpf <bpf@vger.kernel.org>,
	Linux Kernel Network Developers <netdev@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	kernel-team <kernel-team@cloudflare.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <kafai@fb.com>,
	Eric Dumazet <edumazet@google.com>
Subject: Re: [PATCH bpf-next] tcp: bpf: Add TCP_BPF_RCV_SSTHRESH for bpf_setsockopt
Date: Fri, 14 Jan 2022 14:20:50 -0800	[thread overview]
Message-ID: <CABWYdi1p=rRQM3oySw2+N+mcrUq3bXA5MXm8cHmC3=qfCU5SDA@mail.gmail.com> (raw)
In-Reply-To: <CAA93jw5+LjKLcCaNr5wJGPrXhbjvLhts8hqpKPFx7JeWG4g0AA@mail.gmail.com>

On Thu, Jan 13, 2022 at 9:44 PM Dave Taht <dave.taht@gmail.com> wrote:
> Yes, but with the caveats below. I'm fine with you just saying round trips,
> and making this api possible.
> It would comfort me further if you could provide an actual scenario.

The actual scenario is getting a response as quickly as possible on a
fresh connection across long distances (200ms+ RTT). If an RPC
response doesn't fit into the initial 64k of rcv_ssthresh, we end up
requiring more roundrips to receive the response. Some customers are
very picky about the latency they measure and cutting the extra
roundtrips made a very visible difference in the tests.

> See also:
> https://datatracker.ietf.org/doc/html/rfc6928
> which predates packet pacing (are you using sch_fq?)

We are using fq and bbr.

> > Congestion window is a learned property, not a static number. You
> > won't get a large initcwnd towards a poor connection.
> initcwnd is set globally or on a per route basis.

With TCP_BPF_IW the world is your oyster.

  reply	other threads:[~2022-01-14 22:21 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-11 19:29 [PATCH bpf-next] tcp: bpf: Add TCP_BPF_RCV_SSTHRESH for bpf_setsockopt Ivan Babrou
2022-01-11 21:47 ` Song Liu
2022-01-13 22:56   ` Ivan Babrou
2022-01-12 21:01 ` Dave Taht
2022-01-13 22:56   ` Ivan Babrou
2022-01-14  5:43     ` Dave Taht
2022-01-14 22:20       ` Ivan Babrou [this message]
2022-01-15 16:46         ` Dave Taht

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CABWYdi1p=rRQM3oySw2+N+mcrUq3bXA5MXm8cHmC3=qfCU5SDA@mail.gmail.com' \
    --to=ivan@cloudflare.com \
    --cc=andrii@kernel.org \
    --cc=ast@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=dave.taht@gmail.com \
    --cc=edumazet@google.com \
    --cc=kafai@fb.com \
    --cc=kernel-team@cloudflare.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=netdev@vger.kernel.org \


* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).