Fast class reloading

Igor Adam Klimer 150043 at
Wed Jun 2 18:40:27 PDT 2010

Yes, I understand the limitations of an agent. However, it should be possible to modify the VM (within the limitations imposed on the agents) *using* the agent. So in summary: I want to use a "vanilla" agent to modify the VM (that's the part where I'm afraid if an agent is not too limited - because, like you said, we can basically only change method bodies) so that the limitations no longer apply. This would mean that users could use a standard VM that would get "augmented" by the (then still unmodified) agent, so that reloading of classes would be possible.
If my idea still doesn't make sense to you, then it's either really stupid or really unorthodox ;)

Igor Klimer

----- oryginalna wiadomość -----
od: David Holmes <David.Holmes at>
data: czwartek, czerwiec 3, 2010 3:22
temat: Re: Fast class reloading
do: Igor Adam Klimer <150043 at>
kopia do: hotspot-runtime-dev at

> Igor Adam Klimer said the following on 06/02/10 23:16:
> >>An agent can only use functionality exposed by the VM and 
> there is
> >>no VM functionality in existence to do what you want. This has to
> >>be supported by the VM (after which it could be exposed to agents).
> >>
> >
> >Yes, but from what I understood an agent can also modify the VM's
> >classes - so the idea was to exploit that (eh, "exploit" has a bad
> >sound to it ;)) and modify the VM so that it does include the
> >functionality we need. Does this idea seem reasonable to you? Of
> >course, it would be hard to maintain such "patches", but it would
> >take the burden of installing a custom VM from the users.
> That's exactly what I said above. First you have to add the 
> functionality you want to the JVM, then you need to make that 
> functionality available to the agent. Your users will still need 
> your customized VM.
> At present class JVMTI class redefinition is limited in ways 
> that don't meet your list of requirements:
> "The redefinition may change method bodies, the constant pool 
> and attributes. The redefinition must not add, remove or rename 
> fields or methods, change the signatures of methods, change 
> modifiers, or change inheritance."
> David

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