Re: Fix performance on 10Gb networks

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Nov 19 18:18, Iuliu Rus wrote:
>  You are right, of course. We initially thought it has to be a
> multiple of page_size but it doesn't. I just re-tested with 63k and it
> gives good perf too.
> We get 600Mbits/second compared with 10Mb for the old default.
> Attached the modified patch.
> 
> On Tue, Nov 18, 2014 at 8:43 PM, Corinna Vinschen
> <corinna-cygwin@cygwin.com> wrote:
> > Hi Iuliu,
> >
> > On Nov 18 19:30, Iuliu Rus wrote:
> >> Hello,
> >> Google is running Cygwin apps on its 10Gb networks and we are seeing
> >> extremely bad performance in a couple of cases. For example, iperf
> >> with the defaults results in only 10Mbits/sec.
> >> We tracked this down to a combination of non-blocking sockets with
> >> Nagle+delayed ack kicking in, since the apps eventually end up sending
> >> a very small packets (2 bytes).
> >> We have a case open against Microsoft but since everything is moving
> >> very slow we would like to work around by picking socket buffers that
> >> are multiple of 4k.
> >
> > Thanks for the patch.  One question:
> >
> >> Change log:
> >> 2014-11-18 Iuliu Rus <...>
> >>
> >> * net.cc Change default values for socket buffers to fix performance
> >> on 10Gb networks.

Patch applied.


Thanks a lot,
Corinna

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

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