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From: Pedro Inacio <pedro DOT inacio AT honeynet-pt DOT org>
Subject: Re: select() too slow
Date: Sun, 19 Mar 2006 09:54:19 +0000
To: cygwin AT cygwin DOT com
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Yes! I've confirmed that!

With TCP_NODELAY Cygwin and Linux times are similar.
It seems that there is some issue with the Naggle algorithm on  
Windows for sure.

Thanks

Pedro Inacio


On 2006/03/15, at 21:49, Corinna Vinschen wrote:


>
> It looks like this is a TCP_NODELAY issue.  You tend to get the  
> problem
> if a socket is used "interactively", which means, being used for  
> reading
> and writing in arbitrary order.
>
> Unfortunately the Nagle algorithm on Windows is somewhat sluggish.   
> I've
> tried your echo_server with and without Nagle disabled.  Sending a 17
> Megs file from my Cygwin box to an echo_server on my Linux box takes
> between 4 and 5 seconds.
>
> Sending a 17 Megs file from Linux to an echo_server on Cygwin takes
> about 55 seconds.  However, when I disable the Nagle algorithm in the
> echo_server, it takes between 2 and 9 seconds.  I don't understand the
> unexact interval, but I also don't see how that could be Cygwin's  
> fault.
>
>
> --- echo_server.c.ORIG  2006-03-15 22:37:41.905621200 +0100
> +++ echo_server.c       2006-03-15 22:45:56.597789300 +0100
> @@ -62,6 +62,10 @@ int main(void) {
>
>    fcntl(client_fd, F_SETFL, fcntl(client_fd, F_GETFL) | O_NONBLOCK);
>
> +  int opt = 1;
> +  if (setsockopt(client_fd, IPPROTO_TCP, TCP_NODELAY, &opt, sizeof  
> opt) == -1)
> +    fprintf(stderr,"setsockopt TCP_NODELAY: %.100s", strerror 
> (errno));
> +
>    while(1) {
>      FD_ZERO(&read_fds);
>      FD_ZERO(&write_fds);
>
>
> Corinna
>
> -- 
> Corinna Vinschen                  Please, send mails regarding  
> Cygwin to
> Cygwin Project Co-Leader          cygwin AT cygwin DOT com
> Red Hat
>
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