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Date:	Tue, 10 Jan 2012 09:46:10 +0100
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	cygwin AT cygwin DOT com
Subject:	Re: socket performance (was Re: Building cygwin1.dll)
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On Jan  9 17:36, Václav Zeman wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
> 
> On 01/09/2012 02:43 PM, Corinna Vinschen wrote:
> > Johan,
> > 
> > please don't http://cygwin.com/acronyms/#TOFU.  Thanks.
> > 
> > On Jan  4 21:25, Johan van den Berg wrote:
> >> I am very happy to report that increasing the send and receive
> >> buffers has done the job (at least, on a 10MBit link but will be
> >> testing a 100Mbit in a few days). I calculated the ideal size as
> >> per 
> >> http://www.ibm.com/developerworks/linux/library/l-hisock/index.html
> >
> >> 
> > it's nice to know that you could increase the performance by
> > increasing the buffer sizes.  However, I'm reluctant to implement
> > this as a generic option.  As far as I know the socket buffers are
> > taken from nonpaged pool, so generically using 2 Meg buffers will
> > take a lot of precious resources.
> > 
> > I made a test in a local LAN between Linux and a W7 64 bit machine,
> > and I didn't see a lot of difference between 64K, 2 Megs, or
> > letting the OS decide.  So I'm wondering if it's not the best
> > option to let the OS decide starting with Vista and later.
> Testing it on LAN will not show much. The buffer/TCP window size is
> important for high latency * bandwidth product connections.

Right, but that's not the default scenario.  Cygwin's job in this case
is to provide a POSIX socket API.  It neither takes over the job of
the TCP stack, nor does it know the circumstances in which the socket
will be used.  How should it decide what the ideal buffer sizes are?


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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