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From "Xiao-Feng Li" <xiaofeng...@gmail.com>
Subject [DRLVM][GC] parallel compaction and wasted virtual space
Date Sat, 28 Oct 2006 02:02:55 GMT
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?


[1] http://www.cs.technion.ac.il/~erez/Papers/compressor-pldi.pdf

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