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Date: Tue, 7 Feb 2012 12:45:03 +0100
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
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Subject: Re: [ANNOUNCEMENT] Updated: cygwin-1.7.10-1
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On Feb  6 21:39, Magnus Holmgren wrote:
> Corinna Vinschen <corinna-cygwin <at> cygwin.com> writes:
> 
> > - Improve fork/exec performance on 64 bit systems.
> 
> If fork/exec became faster, something else has slowed down noticeably on my
> 64-bit Vista system. Using a fairly fork-heavy build script as the benchmark
> (and running it when nothing needs to be re-built), 1.7.10 is about 25% slower.
> Switching to cygwin1.dll 1.7.9 speeds things up again (and I only changed the
> DLL; it seemed to work fine for this test at least).
> 
> The "while [ 1 ]; do date; done | uniq -c" loop is about 15% faster with 1.7.10
> though.

I can't reproduce this.  I tested with `make clean; make' in a tcsh
build tree, and the 1.7.9 build is always slower, about 20%.

> Lines like these stand out in a quick look in the strace log (about 75 MB):
> 
> 1172898 1173730 [main] sh 1484 child_copy: dll bss - hp 0xEC low 0x611FC000,
> high 0x61230770, res 1
> 
> Every 4-5 print of "child_copy: dll bss" starts with a big number like that
> (values in the 50000-100000 range are more common). Don't know if this is
> relevant...

That hasn't changed between 1.7.9 and 1.7.0.  We always have to copy
parent data to the child in fork.  Sigh.


Corinna

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

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