As some of you may have heard
Monday, 29. October 2007, 12:31:00
As some of you may have heard, we're considering disabling ObjectSpace.each_object by default in JRuby. Primarily, this is for performance; to support each_object, we have to bend over backwards, maintaining lists of weak references to all objects in the system and periodically cleaning out those lists. Here's some example performance, from a fractal benchmark in the JRuby source:
With ObjectSpace: Ruby Elapsed 45.967000
Without ObjectSpace: Ruby Elapsed 4.280000
What's most frustrating about this is that almost *no* libraries or apps use each_object, and it's a terrible performance hit for us.
The one really visible use of each_object is in test/unit, where the default console-based runner does each_object(Class) to find all subclasses of TestCase. Because this is a heavily-used library (to say the least), I've made modifications to JRuby to always support each_object(Class) by maintaining a bidirectional graph of parent and child classes. So that much wouldn't go away (but I'd prefer an implementation that uses Class#inherited, since it would be cleaner, faster, and deterministic).
So...I'm writing this to see what the general Ruby world thinks of us having ObjectSpace disabled by default, enableable via a command line option (or perhaps through a library? -robjectspace?).
I think more and more of you may want to give JRuby another look over the next few months, so I think we need to involve you in such decisions.
With ObjectSpace: Ruby Elapsed 45.967000
Without ObjectSpace: Ruby Elapsed 4.280000
What's most frustrating about this is that almost *no* libraries or apps use each_object, and it's a terrible performance hit for us.
The one really visible use of each_object is in test/unit, where the default console-based runner does each_object(Class) to find all subclasses of TestCase. Because this is a heavily-used library (to say the least), I've made modifications to JRuby to always support each_object(Class) by maintaining a bidirectional graph of parent and child classes. So that much wouldn't go away (but I'd prefer an implementation that uses Class#inherited, since it would be cleaner, faster, and deterministic).
So...I'm writing this to see what the general Ruby world thinks of us having ObjectSpace disabled by default, enableable via a command line option (or perhaps through a library? -robjectspace?).
I think more and more of you may want to give JRuby another look over the next few months, so I think we need to involve you in such decisions.
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