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From "Geir Magnusson Jr." <g...@pobox.com>
Subject Re: [drlvm] Class unloading support
Date Wed, 25 Oct 2006 10:54:12 GMT


Egor Pasko wrote:
> On the 0x20C day of Apache Harmony Aleksey Ignatenko wrote:
>> Hello all!
>>
>>
>>
>> As you probably know current version of harmony DRLVM has no class unloading
>> support. This leads to the fact that some Java applications accumulate
>> memory leaks leading to memory overflow and crashes.
>>
>> In this message I would like to describe two approaches for class unloading
>> in DRLVM and propose to implement one of them as basic. Pros and cons for
>> both approaches are presented below. Lets name these approaches:
>>
>>    1. Mark and scan based approach.
>>    2. Automatic class unloading approach.
> 
> I am +1 to (2)=(Automatic class unloading approach). Do not like
> stop-the-world. 
> 
> But it has 1 more "cons" -- JIT should change it's devirtualizer
> accordingly to the VTable change. Doable, of course.
> 
> BTW, is it reasonable to "compress" or "enumerate" references to
> j.l.Class in each object to reduce the footprint? How many classes are
> alive in heavy-duty applications? not very much probably.

What is your sense of "very much"?  IOW, how many would make you say, 
"yeah, that's a lot"

geir



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