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Re: Re: CGI::Simple vs CGI.pm - Is twice as fast good enough?

by tachyon (Chancellor)
on Feb 16, 2002 at 12:01 UTC ( #145839=note: print w/ replies, xml ) Need Help??


in reply to Re: CGI::Simple vs CGI.pm - Is twice as fast good enough?
in thread CGI::Simple vs CGI.pm - Is twice as fast good enough?

When you use CGI.pm 700 lines of code get 'compiled' plus 2400 lines of code also get put in the subs hash. While the code in the subs hash is not compiled a fairly large hash must be generated which takes both memory and time. CGI::Simple uses SelfLoader to avoid compiling methods that are rarely used. You do this by placing these methods below a __DATA__ token. At compile time compilation stops at the __DATA__ token. As a result when you use CGI::Simple only 300 lines of code actually get compiled.

With SelfLoader if you call one of the methods below the data token then (from the docs):

The SelfLoader will read from the CGI::Simple::DATA filehandle to load in the data after __DATA__, and load in any subroutine when it is called. The costs are the one-time parsing of the data after __DATA__, and a load delay for the _first_ call of any autoloaded function. The benefits (hopefully) are a speeded up compilation phase, with no need to load functions which are never used.

One of the neat things about SelfLoader is that if you know that you will regularly use methods x, y, and z you can easily tune the module by placing these above the data token. As a result they will be available without using SelfLoader and the runtime overhead of using SelfLoader need never be paid.

One of the not so neat things is that you have to load SelfLoader to use it, so there is a compile time penalty that you must pay. Fortunately SelfLoader.pm is only 100 lines of code. I was sorely tempted to 'roll my own' as you can do this with much less code provided you do not have to 'cover all the bases' as the module does. This, however, went against the perl concept of using modular code when available. Similarly CGI::Simple uses IO::File->new_tmpfile() to generate a self destructing temp file for file uploads leaving all the details to this module. IO::File is called via a require so you only load it if and when you need it.

cheers

tachyon

s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print


Comment on Re: Re: CGI::Simple vs CGI.pm - Is twice as fast good enough?
(Ovid) Re(3): CGI::Simple vs CGI.pm - Is twice as fast good enough?
by Ovid (Cardinal) on Feb 16, 2002 at 14:54 UTC

    tachyon wrote:

    CGI::Simple uses SelfLoader to avoid compiling methods that are rarely used. You do this by placing these methods below a __DATA__ token. At compile time compilation stops at the __DATA__ token.

    I didn't notice this part at first. mod_perl scripts cannot contain __DATA__ tokens. Do you have a solution for this? I suppose you can make a separate mod_perl implmentation without the __DATA__ token. Since the performance issue you're resolving is load time, this really doesn't apply in this instance. However, then you have CGI::Simple, CGI::Simple::Standard, and CGI::Simple::mod_perl. I don't see a problem with that if you really need those namespaces to address these issues, but I wonder if others would object.

    Cheers,
    Ovid

    Join the Perlmonks Setiathome Group or just click on the the link and check out our stats.

      Ah says he. Logically you just delete the use SelfLoader and __DATA__ tag. On testing of loadtimes using a version of CGI::Simple without Selfloader and the __DATA__ tag the entire script loads/compiles slower but is still faster than CGI.pm plus all the methods are compiled and ready to go.

      There would seem to be three options. A mod perl version without the __DATA__ tag. Cutting the module into two parts with the less used functions in another module that gets required in a runtime. A CGI.pm type solution.

      I would favour having a CGI::Simple::mod_perl module that is just the standard module without SelfLoader and the __DATA__ tag as this is easiest to maintain and as most scripts need some tuning to use mod_perl so modifying the use CGI::blah should be no big deal.

      In reality under mod_perl there is no good reason not to just use CGI.pm as the load time, size, etc is not an issue and it is well proven.

      cheers

      tachyon

      s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print

        In reality under mod_perl there is no good reason not to just use CGI.pm as the load time, size, etc is not an issue and it is well proven.

        In reality under mod_perl there is no good reason not to just use Apache::Request as it is smaller, faster and it is well proven :)

        --
        Ilya Martynov (http://martynov.org/)

      I didn't notice this part at first. mod_perl scripts cannot contain __DATA__ tokens.

      Since it only applies to scripts which run under Apache::Registry there should be no problems with CGI::Simple and it's usage of __DATA__ under mod_perl.

      --
      Ilya Martynov (http://martynov.org/)

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