[CMake] Status/use of CMake on Cygwin

[David Cole]

Under MSYS, I don’t think it’s a fork thing... I think it’s a file-system thing.


When I run “time cmake --version” twice in a row in the MSYS git bash prompt, I get this:


davidcole at WOK /c/dev
$ time cmake --version
cmake version 2.8.10.2


real    0m0.215s
user    0m0.015s
sys     0m0.046s


davidcole at WOK /c/dev
$ time cmake --version
cmake version 2.8.10.2


real    0m0.070s
user    0m0.015s
sys     0m0.015s


First time is slower, like you measured. Second time is quick. File-system caching effects would explain this.



David




From: Alan W. Irwin
Sent: ‎Monday‎, ‎May‎ ‎20‎, ‎2013 ‎5‎:‎01‎ ‎AM
To: marco atzeri
Cc: cmake at cmake.org

On 2013-05-20 07:51+0200 marco atzeri wrote:

> the slowness at startup on cywin is mainly due the fork
> implementation
> http://cygwin.com/faq/faq-nochunks.html#faq.api.fork
>
> unfortunately windows makes a real fork implementation very inefficient.

Hi Marco:

Your explanation sounds reasonable since it appears all new processes
are started with fork, but do you have a reference for that conclusion
that gives more specifics? All the above URL says is that fork can be
"a little slow" on Cygwin with no timing specifics.

Assuming this is the complete explanation for Cygwin startup latency,
I assume it is also the explanation of the MSYS bash.exe startup
latency (factor of 25 slowdown for startup) for all commands that I
found on Wine (a version of Windows whose developers try very hard to
make an exact clone of Microsoft Windows).  The inefficient fork
explanation would also predict that commands executed under bash.exe
on Microsoft Windows would also show the same startup latency issue.

Can somebody with access to MSYS bash.exe on Microsoft Windows verify
that startup latency by timing "--version" options for standard
commands such as cmake?  If such times on a normal PC are hundreds of
milliseconds than you have confirmed the issue, but if they are only a
few milliseconds (8 on Linux, for example, for my entry level PC
hardware), then you have shown the issue doesn't exist for Microsoft
Windows which would contradict the above inefficient fork explanation.

Alan

__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state
implementation for stellar interiors (freeeos.sf.net); the Time
Ephemerides project (timeephem.sf.net); PLplot scientific plotting
software package (plplot.sf.net); the libLASi project
(unifont.org/lasi); the Loads of Linux Links project (loll.sf.net);
and the Linux Brochure Project (lbproject.sf.net).
__________________________

Linux-powered Science
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