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Re: very poor cygwin scp performance in some situations


I've initiated the post "select() too slow".
The example I've done was a non-blocking tcp echo_server.c and how slow it was on linux compared with cygwin.
In fact after activation oh tcp_nodelay option the times were similar.

Meanwhile I've done another test, I've added ssl on top of that echo_server.c with similar results than on linux, with the tcp_nodelay set, and the results are again against cygwin binary.
On cygwin is too slow. I just don't know where the problem is.

On 2006/03/27, at 19:59, Steven Hartland wrote:

----- Original Message ----- From: "Dave Korn"

On 27 March 2006 16:39, Steven Hartland wrote:
I've done quite a bit of digging and not found any real answers
on why cygwin's scp performance is so poor.
See the thread about "select() too slow" last week for an explanation of the
Nagle algorithm, how windoze's implementation of it appears to be crippling,
and how using TCP_NODELAY can fix everything. (Thread ran from 11 Mar to 19

As a quick and dirty hack I channed set_nodelay into set_nonblock which
seems to be set on all the sockets but unfortunately it doesn't seem to help.
Anyone more familiar with the internals of openssh know where this might


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