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From Xiao-Feng Li <xiaofeng...@gmail.com>
Subject Re: [Arch] Class unloading and VM objects reclaim
Date Thu, 08 Sep 2005 03:23:53 GMT
Archie, thanks for the info, the approach looks like the second one I
suggested. We can take it at first.

Btw, there are some situations I am not sure if the approach you
mentioned is possible. For example, we may want to reclaim also VM
structures for strings that is not associated with a class loader, or
to reclaim some jitted code buffers before the class loader is
unloaded, or sometimes we want to put certain data/codes closely
together for better cache/branch effects. Suggestions?

Thanks,
xiaofeng
==
Intel Managed Runtime Division

On 9/8/05, Archie Cobbs <archie@dellroad.org> wrote:
> Xiao-Feng Li wrote:
> > They are basically two approaches to unload the classes, one is to
> > encode the VM object similarly as App object with a header, then GC
> > can treat them uniformly (almost); the other approach treats class
> > unloading specially, which reclaims a class loader together with all
> > its associated VM objects. The former approach can reclaim as more as
> > possible VM objects (besides other benefits such as code placement)
> > but requires more GC overhead, while the latter approach can reclaim a
> > class loader related objects all together if they are arranged
> > properly.
> 
> You can get the benefits of both approaches using per-class loader
> memory areas like SableVM and JCVM. Each class loader has it's own
> stack of memory. All loader-related memory is allocated from that
> stack (including possibly java.lang.Class objects). Then when you
> unload the loader you free the entire stack at once. During GC you
> treat a class loader's stack as a single giant object. For more info:
> http://jcvm.sourceforge.net/share/jc/doc/jc.html#GC%20and%20Class%20Loaders
> 
> Cheers,
> -Archie
> 
> __________________________________________________________________________
> Archie Cobbs      *        CTO, Awarix        *      http://www.awarix.com
>

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