[Python-Dev] shared data (was: Some thoughts on the codecs...)

[M.-A. Lemburg]

Greg Ward wrote:
> 
> > Go start Perl 100 times, then do the same with Python. Python is
> > significantly slower. I've actually written a web app in PHP because
> > another one that I did in Python had slow response time.
> > [ yah: the Real Man Answer is to write a real/good mod_python. ]
> 
> I don't think this is the only factor in startup overhead.  Try looking
> into the number of system calls for the trivial startup case of each
> interpreter:
> 
>   $ truss perl -e 1 2> perl.log
>   $ truss python -c 1 2> python.log
> 
> (This is on Solaris; I did the same thing on Linux with "strace", and on
> IRIX with "par -s -SS".  Dunno about other Unices.)  The results are
> interesting, and useful despite the platform and version disparities.
> 
> (For the record: Python 1.5.2 on all three platforms; Perl 5.005_03 on
> Solaris, 5.004_05 on Linux, and 5.004_04 on IRIX.  The Solaris is 2.6,
> using the Official CNRI Python Build by Barry, and the ditto Perl build
> by me; the Linux system is starship, using whatever Perl and Python the
> Starship Masters provide us with; the IRIX box is an elderly but
> well-maintained SGI Challenge running IRIX 5.3.)
> 
> Also, this is with an empty PYTHONPATH.  The Solaris build of Python has
> different prefix and exec_prefix, but on the Linux and IRIX builds, they
> are the same.  (I think this will reflect poorly on the Solaris
> version.)  PERLLIB, PERL5LIB, and Perl's builtin @INC should not affect
> startup of the trivial "1" script, so I haven't paid attention to them.

For kicks I've done a similar test with cgipython, the 
one file version of Python 1.5.2:
 
> First, the size of log files (in lines), i.e. number of system calls:
> 
>                Solaris     Linux    IRIX[1]
>   Perl              88        85      70
>   Python           425       316     257

    cgipython                  182 
 
> [1] after chopping off the summary counts from the "par" output -- ie.
>     these really are the number of system calls, not the number of
>     lines in the log files
> 
> Next, the number of "open" calls:
> 
>                Solaris     Linux    IRIX
>   Perl             16         10       9
>   Python          107         71      48

    cgipython                   33 

> (It looks as though *all* of the Perl 'open' calls are due to the
> dynamic linker going through /usr/lib and/or /lib.)
> 
> And the number of unsuccessful "open" calls:
> 
>                Solaris     Linux    IRIX
>   Perl              6          1       3
>   Python           77         49      32

    cgipython                   28

Note that cgipython does search for sitecutomize.py.

> 
> Number of "mmap" calls:
> 
>                Solaris     Linux    IRIX
>   Perl              25        25       1
>   Python            36        24       1

    cgipython                   13

> 
> ...nope, guess we can't blame mmap for any Perl/Python startup
> disparity.
> 
> How about "brk":
> 
>                Solaris     Linux    IRIX
>   Perl               6        11      12
>   Python            47        39      25

    cgipython                   41 (?)

So at least in theory, using cgipython for the intended
purpose should gain some performance.

-- 
Marc-Andre Lemburg
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