From: Dave Taht <dave.taht@gmail.com>
To: Hal Murray <hmurray@megapathdsl.net>
Cc: bloat <bloat@lists.bufferbloat.net>
Subject: Re: [Bloat] SO_SNDBUF and SO_RCVBUF
Date: Wed, 22 Apr 2015 12:28:50 -0700 [thread overview]
Message-ID: <CAA93jw4hmHS7J22RKzFxPjkwgOxOAYg0QXVkq6ioOGvENqhH1g@mail.gmail.com> (raw)
In-Reply-To: <20150422191056.9C7AC406057@ip-64-139-1-69.sjc.megapath.net>
SO_SNDLOWAT or something similar to it with a name I cannot recall,
can be useful.
On Wed, Apr 22, 2015 at 12:10 PM, Hal Murray <hmurray@megapathdsl.net> wrote:
>
>> As I understand it (I thought) SO_SNDBUF and SO_RCVBUF are socket buffers
>> for the application layer, they do not change the TCP window size either
>> send or receive. Which is perhaps why they aren't used much. They don't do
>> much good in iperf that's for sure! Might be wrong, but I agree with the
>> premise - auto-tuning should work.
>
> I sure expect them to do the obvious thing.
>
> man 7 socket says:
>
> SO_SNDBUF
> Sets or gets the maximum socket send buffer in bytes.
>
> It doesn't actually say that turns into the TCP window size.
>
> On Linux, there is a factor of 2 for overhead and whatever.
>
> man tcp says:
> TCP uses the extra space for administrative purposes and inter-
> nal kernel structures, and the /proc file values reflect the larger
> sizes compared to the actual TCP windows.
>
> So it looks like the number you feed it turns into the window size.
>
> A few quick tests with netperf confirm that it is doing something close to
> what I expect but I haven't fired up tcpdump to verify that the window size
> is what I asked for. netperf does print out values that are 2x what I asked
> for.
>
> Yuck. (That's Yuck at Linux, not netperf.)
>
>
> --
> These are my opinions. I hate spam.
>
>
>
> _______________________________________________
> Bloat mailing list
> Bloat@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/bloat
--
Dave Täht
Open Networking needs **Open Source Hardware**
https://plus.google.com/u/0/+EricRaymond/posts/JqxCe2pFr67
next prev parent reply other threads:[~2015-04-22 19:28 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-22 19:10 Hal Murray
2015-04-22 19:26 ` Rick Jones
2015-04-22 19:28 ` Dave Taht [this message]
2015-04-22 21:02 ` Eric Dumazet
2015-04-22 21:05 ` Rick Jones
2015-04-22 21:46 ` Eric Dumazet
2015-04-22 22:20 ` Simon Barber
2015-04-22 23:08 ` Eric Dumazet
2015-04-24 4:37 ` Dave Taht
2015-04-24 4:40 ` Dave Taht
2015-04-24 13:50 ` Eric Dumazet
2015-04-24 14:34 ` Dave Taht
2015-04-24 16:31 ` Rick Jones
2015-04-24 18:41 ` Eric Dumazet
2015-04-24 5:23 ` Eric Dumazet
2015-04-22 21:07 ` Steinar H. Gunderson
2015-04-22 21:42 ` Eric Dumazet
2015-04-22 21:47 ` Dave Taht
2015-04-22 22:11 ` Steinar H. Gunderson
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