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.
next prev parent 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
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