Re: Woah

From: Date: Sun, 09 Sep 2001 02:58:56 +0000
Subject: Re: Woah
References: 1  Groups: php.dev 
Request: Send a blank email to php-dev+get-65521@lists.php.net to get a copy of this message 
Benchmarking the execution time for a single function call by making a page and request it via b is a pretty flawed method.  While it may show that a single aliased call to gettext() doesn't change the execution time of a script by much, it does not say anything about the relative times for execution of a specific function.  You should call the function in  a type loop and average over many executions.  Here's a sample you can try:

strlen.php:
<?

        $a = 'blah';
        while($i < 100000) {
                $b = strlen($a);
                $i++;
        }

?>

gstrlen.php:
<?

        $a = 'blah';
        while($i < 100000) {
                $b = gstrlen($a);
                $i++;
        }
        function gstrlen($str) {
                return strlen($str);
        }

?>


22:54:00(george@wasabi)[~/src/php-4.0.6/ext]> time php /opt/apache/htdocs/strlen.php
X-Powered-By: PHP/4.0.6
Content-type: text/html


0.840u 0.010s 0:00.85 100.0%    0+0k 0+0io 293pf+0w


22:54:17(george@wasabi)[~/src/php-4.0.6/ext]> time php /opt/apache/htdocs/gstrlen.php
X-Powered-By: PHP/4.0.6
Content-type: text/html


1.950u 0.010s 0:01.95 100.5%    0+0k 0+0io 295pf+0w


When done often enough, the difference between calling userland functions and builtins is _huge_.  Substitute your favorite function in for strlen (I tried a bunch), you'll get similair results.  Having to switch executor contexts evertime you call a userland function is really expensive.

George




On Saturday, September 8, 2001, at 08:07 PM, Cristopher Daniluk wrote:


I feel like you're getting a bit personal here, but I'll refrain from doing
the same and simply provide numbers. This is a demonstration to prove purely
the overhead of going into a userspace function that calls an internal
versus calling the internal directly. Obviously this isn't scientific, but
that's not my goal.

3 scripts were created. First called _(""). Second defined a function as
follows:

function b($str) { return gettext($str); }

Third b("") instead of _("") - note the second one was created just to try
and normalize out any deviance from parsing the new function.

Apache Bench was run at 1000 queries to give enough performance to
illustrate a significant deviance. A concurrency of 10 and 100 were used.
Each set was run 3 times and averages were taken to normalize outside
factors. Tests were run randomly at various times throughout the last hour,
to reduce the effect of foreign elements.

First Test (using _)
Concurrency 10: 50.24/50.23/57.43 = 52.63
Concurrency 100: 44.58/46.59/44.53 = 46.23

Second Test (defining b)
Concurrency 10: 55.05/56.19/50.55 = 53.93
Concurrency 100: 45.65/47.06/45.71 = 46.12

Third Test (using b)
Concurrency 10: 55.16/55.82/52.16 = 54.38
Concurrency 100: 46.74/46.39/47.19 = 46.77

I really truly and with all my heart believe that if simply calling a user
created function could drop performance by 25%, PHP would not be a viable
language. Whether my results are accurate findings or not, Rasmus's
demonstration of a 26.3% performance decrease by CALLING A FUNCTION is a lot
to swallow!

Oh, and I'll refrain from making the muse that the latter test was faster.

Having the user make their own function may not be the right solution for
this problem, but its phenomenally silly to argue that it would have a large
performance impact!

Regards,


Cristopher Daniluk
President & CEO
email: cris@dsnet.net
direct: 330/530-2373

Digital Services Network, Inc
Unleashing Your Potential
voice: 800/845-4822
web: http://www.dsnet.net/


-----Original Message-----
From: Chuck Hagenbuch [mailto:chuck@horde.org]
Sent: Saturday, September 08, 2001 7:23 PM
To: cris@dsnet.net
Cc: 'PHP Developer List'
Subject: RE: [PHP-DEV] Woah


Quoting Cristopher Daniluk <cris@dsnet.net>:


Agreed, but is the speed loss really worth crying about?


Obviously not to you, but I'm pretty sure you came down in the category of
people who'd never used gettext.


It is negligible calling a userspace function versus an internal compared

to

the greater work that the typical PHP script does.


What authority do you have to make this statement? Rasmus posted numbers.
Where
are yours?

-chuck

--
Charles Hagenbuch, <chuck@horde.org>
Some fallen angels have their good reasons.

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