From: Simon Krahnke <overlord@...>
Date: 2007-08-14T09:05:03+09:00
Subject: Re: Why don't Ruby libraries share memory?

* Matt Harvey <matt@teamdawg.org> (22:19) schrieb:

> Sorry, I started talking about Rails again. The question is not about
> Rails. The questions are: Is there any way we can have shared Ruby
> libraries without turning the relevant code into a C extension? Is it
> necessary that code be compiled to be put into shared memory by the
> OS?

C-libraries have 2 nice features: They are read only, and ready to use
in a disk file. So a modern OS can just map that file into memory and
use the same physical memory for every process accessing the file.

Ruby classes aren't read only. But you could just write the changes into
memory and keep the constant part in a file. So the real problem is that
the source aren't ready to use for a modern interpreter. The data
structures the compiler works on are nowhere on disk, they are
dynamically created when the source files are evaluated.

The source files don't hog up memory, they can be freed after being
parsed or just memory mapped. It's the parsers result, the structures
the interpreter works on, that need the memory.

Ruby would have to use "precompiled" source files to be able to use
memory mapping. It could use copy-on-write to dynamically change the
code. There still much work on Ruby, so there may be a chance for that.

mfg,                             simon .... l