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Date: Sat, 28 May 2005 14:57:20 -0400
From: Christopher Faylor <cgf-no-personal-reply-please AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: Serious performance problems (Gerrit/Danny please comment)
Message-ID: <20050528185720.GA3015@trixie.casa.cgf.cx>
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References: <4297A14B DOT 9070409 AT plausible DOT org> <20050528131501 DOT V53507 AT logout DOT sh DOT cvut DOT cz>
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On Sat, May 28, 2005 at 01:24:31PM +0200, Vaclav Haisman wrote:
>Somebody mentioned that malloc implementation could be the problem. Dunno. I
>has also crossed my mind that another difference between FreeBSD and Cygwin is
>implementation of C++ exceptions. Maybe the SJLJ implementation that Cygwin
>AFAIK uses has too big overhead.

To test this theory, I just tried replacing Cygwin's "Unwind" functions
with those from mingw and saw a noticeable speed up in the execution of
this program.  I did this by extracting the contents of mingw's libgcc
to a directory and then including unwind-c.o and unwind-sjlj.o on the
command line when linking the test case.  I had to modify the test case
by adding these two lines to the bottom:

  int __mingwthr_key_dtor;
  int _CRT_MT;

to avoid undefined symbol errors so this is obviously not intended as a
complete solution.

On doing this, the program went from taking 25 seconds to execute to
taking 7 seconds to execute.  That's still 4x slower than mingw but it
is, nonetheless, a noticeable difference.

Gerrit and Danny do you know what the difference between the mingw and
cygwin implementations of these functions might be?

cgf

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