This repository contains a copy of Jikes RVM patched with an implement of the Sapphire garbage collection algorithm.
This implementation is the result of research and technical work by:
- Laurence Hellyer
- Tomoharu Ugawa (Kochi University of Technology)
- Carl G. Ritson (University of Kent)
- Richard E. Jones (University of Kent)
Please contact Carl Ritson or Richard Jones for more information.
Sapphire is an on-the-fly concurrent copying garbage collector. This means it does not need to stop all user threads to perform garbage collection. Thread stacks are scanned individually. This leading to sub-millisecond pause times during garbage collection.
Sapphire was designed by Richard Hudson and Eliot Moss. It is documented in a journal paper here.
This implementation was performed with permission from Intel who hold patents on Sapphire's design.
The official Jikes RVM website and repository can be found here.
Standard Jikes RVM dependencies apply for building with ant (see here).
To build optimised (adjust host.name appropriately):
ant -Dhost.name=x86_64-osx -Dconfig.name=FastAdaptiveOTFSapphire
To build debug (adjust host.name appropriately):
ant -Dhost.name=x86_64-osx -Dconfig.name=ExtremeAssertionsBaseBaseOTFSapphire
RVM will be in the dist directory.
The following options can be used to changed Sapphire's run-time behaviour.
Select the method used for copying concurrent with the mutator, e.g.
-X:gc:concurrentCopyMethod=always-htm2
| value | description |
|---|---|
| cas / cas2 | default per-word synchronised methods |
| unsafe / unsafe2 | unsynchronised methods |
| stm / mstm / stmseq / stmseq2 / stmseq2p / stmseq2n | software transactional |
| htm / htm2 / mhtm | hardware transactional |
All of these options can be prefixed with "always-" to force the method to be used for all collections. Normally stop-the-world collection will default to unsafe2. Methods postfixed with 2 use a more efficient copying order than the same method without the postfix.
Select the size of transactions for mhtm and mstm concurrent copying methods, e.g.
-X:gc:concurrentCopyTransactionSize=256
Select the method used to trigger concurrent collection, i.e. when collection will be started. Interacts with ConcurrentTrigger.
-X:gc:concurrentTriggerMethod=allocation
| value | description |
|---|---|
| allocation | pages allocated since last collection start |
| OOGCAllocation | pages allocated since last collection end |
| percentage | percentage of the heap allocated |
| period | microseconds since last collection start |
| time | microseconds since last collection end |
Value used with ConcurrentTriggerMethod may represent pages, time or a percentage.
Force one or more Sapphire phases to run stop-the-world, e.g.
-X:gc:SapphireSTWPhase=flip
One or more of the following separated by commas:
- alloc
- copy
- flip
- root