Re: subprocess_env

[Doug MacEachern <do...@covalent.net>]

On Thu, 8 Jun 2000, Ian Kallen wrote:

> 
> I'm using a third party module that writes a bunch of variables to the
> subprocess_env table to setup data for the request. It has us making
> repeated class method calls like this (for our usage with Mason):
> <% Blah::foo('bletch') %>
> 
> where foo is in the Blah package merely doing this:
> 
> sub foo {
>     my($s) = @_;
>     my($r) = Apache->request();
>     return $r->subprocess_env('foo_' . $s);
> }
> 
> I'm thinking of changing the behvior to 
> <% $ENV{'foo_bletch'} %>
> but foo_bletch isn't in the %ENV hash, so I'm looking at initializing
> every request to do this:
> $r->subprocess_env->do(
>  sub { my($k,$v)=@_;
>    $ENV{$k}=$v;
>  1; 
>  }
> );
> to eliminate repeated accesses of the subprocess_env table; one call
> populates %ENV and that's it.
> 
> Now, I don't want to kick off a debate on the performance problems that
> reading/writing to the environment incur; I didn't design this behavior
> I just want to make the best of it since this is what the application
> requires of us. I just need to optimize access to the environment by
> turning the dozen or so calls per request to Blah::foo to just %ENV.  
> 
> Any ideas regarding the expense of mulitple $r->subprocess_env vs.
> accessing %ENV?

%ENV will probably be faster for lookups, since subprocess_env has the
overhead of calling a perl subroutine (pp_entersub).  it's the population
of %ENV that can be expensive.  you might be better off populating a
non-magic global, such as %Env.