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From "Ivan Volosyuk" <ivan.volos...@gmail.com>
Subject Re: [DRLVM][GC] parallel compaction and wasted virtual space
Date Sat, 28 Oct 2006 16:07:04 GMT
Excellent algorithm. I think it makes sense to implement it. If we
can't use on 32 bit machines with plenty of ram, we can use it on 64
bit machines.
What about enabling the algorithm at runtime if required conditions
are met, otherwise falling back to some other algorithm?

On 10/28/06, Xiao-Feng Li <xiaofeng.li@gmail.com> wrote:
> Hi, all, the plan for GCv5 parallel compaction is to apply the idea of
> Compressor [1]. But it has an issue I want to discuss with you.
> Compressor needs to reserve an unmapped virtual space for compaction.
> The size of the reserved part is the same as that of copy reserve
> space in a semi-space collector. This means about that part of the
> virtual space is unusable for the JVM. In a typical setting, the
> wasted part is half size of the total compaction space. If we have 1GB
> physical memory, the JVM is ok for Compressor because the virtual
> space is large enough to wast half; but if the phsical memory is >2GB,
> Compressor may have a problem in 32bit machine: some of phsical mapped
> space might be wasted.
> Any opinion on this?
> Thanks,
> xiaofeng
> [1] http://www.cs.technion.ac.il/~erez/Papers/compressor-pldi.pdf

Intel Enterprise Solutions Software Division

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