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Date: Mon, 10 Dec 2007 15:03:34 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
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Subject: Re: Updated: cygwin-1.5.25-5
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On Dec 10 08:40, Mike Marchywka wrote:
> > I can't reproduce worse I/O performance. I tested different scenarios
> > with lots of disc I/O and the performance was identical between 1.5.24
> > and 1.5.25 within the bounds of a performance test.
> >
> 
> 
> One thing I found out, after originally blaming my inner computational loops,
> was that console IO is very slow. Using ">" on the command line makes a big
> difference compared to opening a destination file. This seemed to be the
> speed limit in many programs I thought were computationally limited. 
> [...]
>   Has the console buffering
> changed lately? 

I don't understand what you mean.  Using > on the command line or
opening the file by using some option of the tool has both nothing to do
with console output.  In both cases a file is opened.  The only
difference in that in the > case the shell opens the file and the child
inherits the file descriptor, in the other case the child opens the file
by itself.  However, I don't see how getting a file descriptor to a file
from the parent should be different than opening the file in the child,
at least as long as parent and child are both Cygwin processes.

In fact, one of my tests was a loop using `cat < foo > bar', which got
much faster under 1.5.25 due to the new 64K buffering.

Give me a really simple testcase which shows reproducibly worse
performance on 1.5.25 compared to 1.5.24 and I'll have another look.


Corinna

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

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