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Hi, I'm using MP v2.000002, along with ActivePerl
v5.8.8 and Apache v2.054, all that under Windows XP.
Under Win32, the Apache memory model is a threaded
model, i.e. we have one master Apache process,and, then, one unique child
process, containing several threads, that can, if needed, use Perl Interpreters
taken from an interpreter pool.
This is what I have understood so far.
So, I'm trying to understand what's really shared
when preloading modules from httpd.conf, and which benefits I could get from
doing that.
The problem is that I can't really understand
what's kept shared when new Perl interpreters are started.
From the MP docs, I have read that, among
others:
Care is taken by Perl to copy only mutable data,
which means that no runtime locking is required and read-only data such as the
syntax tree is shared from the parent, which should reduce the overall mod_perl
memory footprint.
I made tests to understand that. For example, a
simple basic test has been to create a module with a simple basic
sub:
########################
package Modules::MyPack;
sub test{ 1; } 1; ######################## Then, I preloaded it in the parent process,
including a "PerlRequire Modules/MyPack.pm" in httpd.conf.
At last, I wanted to make a test in a siple script,
like that:
######################## my $sub = \&Modules::MyPack::test;
open FILE, ">>", "test.txt"; print FILE $sub, "\n"; close FILE; ######################## The purpose of this test is to see what is the
actual memory address of &Modules::MyPack::test.
I ran this test with 3 concurrent Perl Intepreters
and noticed that the returned address is different for each of them, which makes
me think that there isn't any memory sharing, even for a simple preloaded
subroutine. Indeed, I would have believed, if this very basic subroutine had
been shared among intepreters, them to have the same actual memory
address.
Am I getting wrong?
What's actually being shared among intepreters? How
could I simply test the fact stuff is actually shared?
Thanks in advance,
Lionel.
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