From: Charles Oliver Nutter <charles.nutter@...>
Date: 2007-10-29T21:02:56+09:00
Subject: Re: JRuby disabling ObjectSpace: what implications?

mortee wrote:
> Charles Oliver Nutter wrote:
>> Actually, we do that a bit already. For example, we do not track arrays
>> constructed during argument processing, since they are typically
>> transient. The problem is that we could only choose to track all Ruby
>> objects, for example...which would cripple other JRuby apps running in
>> the same process.
> 
> [...]
> 
>> The problem is not so much that the object references move as that you
>> would have to lock the memory locations for some period of time to be
>> able to walk the object table. And I think that's *bad* especially when
>> we're looking at JRuby allowing folks to run dozens of apps in the same
>> process and memory space out of the box. We can't lock things down like
>> that.
> 
> Sorry for the extremely uninitiated and naive question - but when you're
> about to enumerate each object in an application, aren't you interested
> only in this application's objects anyway? So why would you have to lock
> anything about the other ruby apps in the same process? Is that kind of
> distinguishing objects impossible on the GC/enumeration level?

As far as I know there's no way to have JVMTI enumerate only objects 
created by a specific application in a given JVM. So any sort of 
ObjectSpace impl based on it would have to take that into consideration.

- Charlie