TUNING
A little tuning can go a long way, and can make the difference between
a web site that gets by, and a site that screams with speed. With
Apache::ASP, you can easily take a poorly tuned site running at
5 hits/second to 25+ hits/second just with the right configuration.
Documented below are some simple things you can do to make the
most of your site.
For more tips & tricks on tuning Apache and mod_perl, please see the tuning
documents at:
Vivek Khera's modperl performance tuning
http://perl.apache.org/tuning/
Stas Beckman's modperl Guide
http://perl.apache.org/guide/
$Application & $Session State
Use NoState 1 setting if you don't need the $Application or $Session objects.
State objects such as these tie to files on disk and will incur a performance
penalty.
If you need the state objects $Application and $Session, and if
running an OS that caches files in memory, set your "StateDir"
directory to a cached file system. On WinNT, all files
may be cached, and you have no control of this. On Solaris, /tmp is cached
and would be a good place to set the "StateDir" config setting to.
When cached file systems are used there is little performance penalty
for using state files.
High MaxRequests
Set your max requests per child thread or process (in httpd.conf) high,
so that ASP scripts have a better chance being cached, which happens after
they are first compiled. You will also avoid the process fork penalty on
UNIX systems. Somewhere between 100 - 1000 is probably pretty good.
Precompile Scripts
Precompile your scripts by using the Apache::ASP->Loader() routine
documented below. This will at least save the first user hitting
a script from suffering compile time lag. On UNIX, precompiling scripts
upon server startup allows this code to be shared with forked child
www servers, so you reduce overall memory usage, and use less CPU
compiling scripts for each separate www server process. These
savings could be significant. On my PII300, it takes a couple seconds
to compile 28 scripts upon server startup, with an average of 50K RAM
per compiled script, and this savings is passed on to the child httpd
servers.
Apache::ASP->Loader() can be called to precompile scripts and
even entire ASP applications at server startup. Note
also that in modperl, you can precompile modules with the
PerlModule config directive, which is highly recommended.
Apache::ASP->Loader($path, $pattern, %config)
This routine takes a file or directory as its first arg. If
a file, that file will be compiled. If a directory, that directory
will be recursed, and all files in it whose file name matches $pattern
will be compiled. $pattern defaults to .*, which says that all scripts
in a directory will be compiled by default.
The %config args, are the config options that you want set that affect
compilation. These options include Debug, Global, GlobalPackage,
DynamicIncludes, StatINC, and StatINCMatch. If your scripts are later
run with different config options, your scripts may have to be recompiled.
Here is an example of use in a *.conf file:
<Perl>
Apache::ASP->Loader(
'c:/proj/site', "(asp|htm)\$",
Global => '/proj/perllib',
Debug => 1, # see output when starting apache
# OPTIONAL configs if you use them in your apache configuration
# these settings affect how the scripts are compiled and loaded
GlobalPackage => SomePackageName,
DynamicIncludes => 1,
StatINC => 1,
);
</Perl>
This config section tells the server to compile all scripts
in c:/proj/site that end in asp or htm, and print debugging
output so you can see it work. It also sets the Global directory
to be /proj/perllib, which needs to be the same as your real config
since scripts are cached uniquely by their Global directory. You will
probably want to use this on a production server, unless you cannot
afford the extra startup time.
To see precompiling in action, set Debug to 1 for the Loader() and
for your application in general and watch your error_log for
messages indicating scripts being cached.
No .htaccess or StatINC
Don't use .htaccess files or the StatINC setting in a production system
as there are many more files touched per request using these features. I've
seen performance slow down by half because of using these. For eliminating
the .htaccess file, move settings into *.conf Apache files.
Instead of StatINC, try using the StatINCMatch config, which
will check a small subset of perl libraries for changes. This
config is fine for a production environment, and if used well
might only incur a 10-20% performance penalty.
Turn off Debugging
Turn debugging off by setting Debug to 0. Having the debug config option
on slows things down immensely.
RAM Sparing
If you have a lot of scripts, and limited memory, set NoCache to 1,
so that compiled scripts are not cached in memory. You lose about
10-15% in speed for small scripts, but save at least 10K per cached
script. These numbers are very rough. If you use includes, you
can instead try setting DynamicIncludes to 1, which will share compiled
code for includes between scripts.