about-simplified-lxr

name	about-simplified-lxr
description	Useful information about the simplified LXR GC implementation in mmtk-core and mmtk-openjdk.

Simplified LXR GC

lxr-x/simplified branch in mmtk-core and lxr-x/jdk21-simplified branch in mmtk-openjdk contain the implementation of the LXR garbage collector.

lxr-x/simplified in mmtk-core is based on tag v0.32.0 lxr-x/jdk21-simplified in mmtk-openjdk is based on tag v0.32.0-jdk-21

The two branches are forked from the original LXR GC implementation. Both branches contains the core LXR GC algorithm without additional optimizations and features.

Note: The simplification process is still ongoing, and the branches may not be fully simplified yet. You can refer to the commit history and the current progress section for more details on what has been simplified so far.

The purpose of the simplification is to make easier to upstream, although the performance may not be as good as the original one.

Assume the upstream is at v0.32.0 and v0.32.0-jdk-21.

Testing

Use test-simplified-lxr skill to test and verify LXR GC.

Debugging

Refer to the test-simplified-lxr skill on how to run the benchmarks and verify the correctness of the simplified LXR GC.

To fix a crashing benchmark, you have the following options:

1. Use debug build (without --release) to get more debug info
2. Use GDB: add --gdb --no-interactive to the command, and it will automatically run the program in gdb, and print the backtrace if it crashes.
3. Inspect crash logs: hs_err_pid*.log

PRECAUTIONS

• Don't commit, push, revert, or create/edit PRs or issues, unless the user explicitly ask you to do so.
• Do simplifications/refactorings one piece at a time. Don't aim to solve everything in one session.
• Benchmarks can run in parallel, but don't build jdk when other benchmarks or build task are still running.
• Do a cargo fmt under either mmtk-core/ or mmtk-openjdk/mmtk before finish.

Additional User Messages

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