MMTk 0.32.0

0.32.0 (2026-02-04)

What's Changed

Plan

• Compressor
  • Add a stop-the-world, serial Compressor by @no-defun-allowed in #1340
  • Add a parallel/regional Compressor by @no-defun-allowed in #1372
  • Fetch before trying to atomically mark in Compressor by @no-defun-allowed in #1438
• Concurrent Immix
  • Concurrent Immix by @tianleq in #1355
  • Schedule VMProcessWeakRefs in ConcurrentImmix. by @wks in #1403

Policy

• Make chunk map as global side metadata, and each space only lists its own chunks using chunk map by @qinsoon in #1304
• Allow configuring each Immix space to be non moving by @qinsoon in #1305
• Use ChunkMap in MallocSpace by @qinsoon in #1312
• LOS: Reduce is_mapped calls during VO bit scan by @wks in #1341
• Remove dead code about vm space in immortal space by @qinsoon in #1363
• Fix LargeObjectSpace::initialize_object_metadata by @wks in #1393
• Refactor Space::acquire by @wks in #1401
• Fix LOS object enumeration by @wks in #1412
• Implement debug_print_object_info for ImmortalSpace by @qinsoon in #1423

Allocator

• Minor refactor to remove duplicate code using ReservedAllocators by @qinsoon in #1309
• Add alloc_with_options by @qinsoon in #1218

Scheduler

• Minor changes to the ProcessRootNode work packet by @wks in #1327
• Rename Workbucket's active flag to open, add enable flag by @qinsoon in #1373
• Remove GCRequester, move related code to GCTrigger by @qinsoon in #1405

Documentation

• Fix typos and vague statements in weakref doc by @wks in #1329
• Wrong example in print_obj_info.md by @qinsoon in #1358
• Fix doc comments in options module by @k-sareen in #1389
• Add a debugging tip on traversing object graph by @qinsoon in #1396
• Update doc comment for Slot by @wks in #1409
• Document supported platforms by @wks in #1431

CI

• Remove V8 tests from extended tests by @qinsoon in #1313
• Bump Ruby binding test image to 24.04 by @wks in #1326
• Use canary binary by @qinsoon in #1384
• Let CI use both OpenJDK 11 and OpenJDK 21 by @wks in #1419
• Print more info for debugging in get-merged-pr by @qinsoon in #1428
• Allow retry in get-merged-pr by @qinsoon in #1427
• Use ci-perf-kit 0.8.6 (new epoch for CI runner package update on 5th Jan) by @qinsoon in #1444

Misc

• Choose Non-moving Policy based on features by @qinsoon in #1308
• Add a function to print object info from the space for debugging by @qinsoon in #1269
• Remove dead field in VMMap by @k-sareen in #1320
• Move inside_harness to GlobalState by @k-sareen in #1321
• Remove env_var and command_line from options by @wks in #1240
• Use EnumMap::from_fn by @wks in #1323
• Remove the immix_stress_copying feature. Replace with separate options. by @qinsoon in #1324
• Make scan_non_zero_values_fast scan entirely forwards by @no-defun-allowed in #1332
• Move lint config to Cargo.toml. Adapt to Rust 1.88 by @qinsoon in #1335
• SFTSpaceMap should do range check in get_checked by @wks in #1339
• Replace FragmentedMapper with TwoLevelMmapper by @wks in #1337
• Deduplicate specs in SideMetadataSanity::get_all_specs by @qinsoon in #1342
• Workaround eBPF errors by @wks in #1350
• Enable reference processing in the core by default by @k-sareen in #1360
• Fix Clippy 1.89 warnings by @wks in #1367
• Fix rayon-core version for MSRV by @qinsoon in #1368
• Use bytemuck::Zeroable for zeroable types. by @wks in #1371
• Refactor log bits by @qinsoon in #1364
• eBPF probes for finalization and reference processing by @wks in #1374
• Refactor both Mmapper impls into ChunkStateMmapper by @wks in #1369
• Remove unused methods and types related to memory mapping by @wks in #1383
• Add AllInSet affinity kind for pinning threads to all cores in a set by @k-sareen in #1386
• Fix Clippy 1.90 warning by @wks in #1394
• Warn the user about aliasing effect by @wks in #1392
• Remove vim modeline, move current_pause_determined to gc by @qinsoon in #1395
• Use u8 for alignment value by @qinsoon in #1399
• Use boolean allocation options by @wks in #1400
• Fix typo by @wks in #1404
• Pin the dep home to 0.5.5 by @qinsoon in #1411
• Fix Clippy 1.91 warnings. by @wks in #1413
• Pin mdbook/mdbook-admonish version by @qinsoon in #1416
• fix: do not force turn off log in release mode by @playX18 in #1415
• Fix Clippy warnings for Rust 1.92 by @wks in #1435
• Move to Rust 1.92. Bump MSRV to 1.84. by @qinsoon in #1440
• Cleaning up after bumping Rust MSRV by @wks in #1442

New Contributors

• @no-defun-allowed made their first contribution in #1332
• @playX18 made their first contribution in #1415

Full Changelog: v0.31.0...v0.32.0

MMTk 0.31.0

0.31.0 (2025-04-17)

What's Changed

Plan

• Remove dead trace_object methods. by @wks in #1277
• implement mutator builder by @tianleq in #1287
• Fix incongruent defaults for copying GCs by @k-sareen in #1296

Policy

• Clear stale line mark state by @tianleq in #1268
• Ensure log bits are correctly maintained by @k-sareen in #1169

Scheduler

• Make work packet buffer size configurable from one location by @k-sareen in #1285
• Make EDGES_WORK_BUFFER_SIZE constant public to bindings by @k-sareen in #1291

CI

• Fix Clippy warning in 1.84.0 by @wks in #1262
• Fix julia extended tests by @qinsoon in #1270
• Fix to bytemuck_derive 1.8.1 by @qinsoon in #1288
• Fix lychee command by @wks in #1286
• Fix clippy warnings for Rust 1.86 by @wks in #1297
• Properly handle multiple plans in GITHUB-CI in CI scripts by @qinsoon in #1301

Documentation

• Special topic chapter for finalizers and weak references by @wks in #1265
• User Guide chapter for address-based hashing by @wks in #1294

Misc

• Move to Rust 1.83 by @qinsoon in #1253
• Unique object enqueuing option by @wks in #1255
• Fix a subtraction overflow in get_free_pages. by @wks in #1261
• Force fixed heap size when using NoGC by @wks in #1264
• Make GC triggering and heap resizing consistent by @wks in #1266
• Bump MSRV to 1.74.1 by @wks in #1276
• Fix clippy warning about operator precedence by @wks in #1280
• Fixing MSRV-breaking dependencies by @wks in #1284
• Check if an object is in our heap before using VM map during counting live bytes by @qinsoon in #1289
• Aggregate live bytes info in on_gc_finished by @qinsoon in #1292
• Fix broken stats gathering code if no. of GCs > MAX_PHASES by @k-sareen in #1295
• Fix contiguous chunk iterator in monotonic PR by @wks in #1299

Full Changelog: v0.30.0...v0.31.0

MMTk 0.30.0

0.30.0 (2024-12-20)

What's Changed

Policy

• Allow setting object metadata for VM space objects. Expose VO bit under a feature. by @qinsoon in #1248

Misc

• Fix clippy warnings for Rust 1.83 by @wks in #1242
• Annotate mmap ranges using PR_SET_VMA by @wks in #1236
• Fix warnings for lifetime in MmapAnnotation impl by @qinsoon in #1244
• Collect live bytes per space, and report by space by @qinsoon in #1238
• Minor changes for debugging. by @wks in #1245
• Use macos-15 for style check by @qinsoon in #1249
• Check the option before aggregating live bytes data. Panic if the option is enabled on malloc space. by @qinsoon in #1250

Full Changelog: v0.29.0...v0.30.0

MMTk 0.29.0

0.29.0 (2024-11-08)

What's Changed

CI

• Install cargo-msrv using stable toolchain. by @wks in #1215
• Update CI macos image by @qinsoon in #1216
• Performance history canary by @wks in #1209
• Change the default testing branch for Julia tests by @qinsoon in #1221
• Fix auto merge branches by @qinsoon in #1230

Documentation

• Document the policy about performance testing environment and epochs by @qinsoon in #1206

Misc

• Fix a race between forwarding bits and VO bits. by @wks in #1214
• Remove space for nogc link by @Pat-Lafon in #1217
• Make env_logger an optional dependency by @wks in #1226
• Use modern syntax for optional dependencies by @wks in #1229
• Fix nightly build and add inline attributes to {un,}likely by @k-sareen in #1228

New Contributors

• @Pat-Lafon made their first contribution in #1217

Full Changelog: v0.28.0...v0.29.0

MMTk 0.28.0

0.28.0 (2024-09-27)

What's Changed

API

• Require ObjectReference to point inside object by @wks in #1195
• Return if a GC ran or not for handle_user_collection_request by @k-sareen in #1205

CI

• Update ci-perf-kit to 0.7.6 by @qinsoon in #1199
• Update ci-perf-kit to plot epoch by @qinsoon in #1208

Misc

• Skip iterating through unallocated memory for MonotonePageResource by @k-sareen in #1189
• Fix find_last_non_zero_bit, and align metadata address before converting to data address. by @qinsoon in #1188
• Panic message and outdated comments by @wks in #1191
• Filter the result for find_prev_non_zero_value_fast to make sure it is in the search range by @qinsoon in #1192
• Assert OBJECT_REF_OFFSET_LOWER_BOUND invariant by @wks in #1194
• Minor fixes by @wks in #1196
• Add a feature immix_stress_copying by @qinsoon in #1202
• Update migration guide for #1205 by @qinsoon in #1211

Full Changelog: v0.27.0...v0.28.0

MMTk 0.27.0

0.27.0 (2024-08-09)

What's Changed

Policy

• Clear pin bits by @udesou in #1166
• Set the unlog bits for objects in the bootimage by @k-sareen in #1168
• Fix bug in line mark when MARK_LINE_AT_SCAN_TIME=false by @k-sareen in #1171

API

• Require object reference to be aligned by @qinsoon in #1159
• Internal pointer support by @qinsoon in #1165
• Heap traversal by @wks in #1174

CI

• Parallelize and workaround CI style checks by @wks in #1184

Misc

• Extensible eBPF timeline attributes by @wks in #1162
• Only map with executable permissions when using code space by @k-sareen in #1176
• Fix style check for Rust 1.80 by @qinsoon in #1178
• Extra assertions for mutators and epilogues by @wks in #1182
• Refactor iterate_meta_bits by @wks in #1181

Full Changelog: v0.26.0...v0.27.0

MMTk 0.26.0

0.26.0 (2024-07-01)

What's Changed

Policy

• Clear side forwarding bits properly by @wks in #1138
• Fix mark bit clearing in PrepareChunkMap by @wks in #1148
• Let MarkSweepSpace use BlockPageResource by @wks in #1150
• Add SweepChunk to native MarkSweepSpace by @wks in #1158

API

• Rename edge to slot by @wks in #1134

Documentation

• Fix broken link and stale descriptions in doc by @wks in #1139
• API migration guide. by @wks in #1133
• Add back DummyVM as a part of the porting guide. Minor changes to MMTk initialization in the porting guide. by @qinsoon in #1142
• Fix broken link to mmtk.h by @wks in #1149

Misc

• Fix clippy warnings for Rust 1.79 by @wks in #1151
• Display number of slots in timeline visualization by @wks in #1154

Full Changelog: v0.25.0...v0.26.0

MMTk 0.25.0

0.25.0 (2024-05-17)

What's Changed

Plan

• Allow roots to be pinned for StickyImmix nursery collections by @k-sareen in #1108
• Check FULL_NURSERY_GC for StickyImmix as well by @k-sareen in #1124

Policy

• Remove data race for marksweep block lists by @qinsoon in #1112

Scheduler

• Remove coordinator and support forking by @wks in #1067

API

• Allow nursery size to be proportional to the heap size by @qinsoon in #1087
• Remove NULL ObjectReference by @wks in #1064
• Fix write barrier parameter type by @wks in #1130
• Allow querying if the current GC may move objects. by @wks in #1128

CI

• Use host toolchain and explicit target in CI script by @wks in #1109
• Fix ignores in merge check by @qinsoon in #1117
• Fix the openjdk test name in merge check by @qinsoon in #1119

Misc

• Bump dependencies after version 0.24 by @wks in #1105
• Don't use PROT_EXEC with mmap on macos by @eileencodes in #1110
• Rename associated types in GCWorkContext by @wks in #1116
• Add missing pinning metadata to mock_vm by @wks in #1121
• Use to_address for SFT access by @wks in #1122
• Ensure reference objects are either traced or cleared by @wks in #1126
• Dump process map on mmap failure and fix typos by @k-sareen in #1127
• Fix compiler errors and warnings for Rust 1.78.0 by @wks in #1132
• Remove fl_map and refactor FreeListPageResoure by @wks in #953

New Contributors

• @eileencodes made their first contribution in #1110

Full Changelog: v0.24.0...v0.25.0

MMTk 0.24.0

0.24.0 (2024-04-08)

What's Changed

Misc

• Check and fix broken links in docs by @qinsoon in #1085
• Allow binding to implement GC trigger by @qinsoon in #1083
• Resolve issues for unit tests on 32 bits by @qinsoon in #1095
• Use SFTDenseChunkMap on 64bits when vm_space is enabled by @qinsoon in #1094
• Fix warnings with the stable Rust toolchain by @wks in #1099
• Use proper logging for the treadmill by @wks in #1101

Full Changelog: v0.23.0...v0.24.0

MMTk 0.23.0

0.23.0 (2024-02-09)

What's Changed

API

• Ask from binding if GC is disabled by @udesou in #1075

CI

• Stop using the deprecated set-output in our CI configs by @qinsoon in #1059
• Rename CI tests to minimal/extended tests by @qinsoon in #1073
• Properly get PR number for merge group by @qinsoon in #1077

Misc

• MMTk Enhancement Proposal by @wks in #1056
• Timeline visualization tool by @wks in #1022
• Add a document for project principles by @qinsoon in #1069
• Fix un-cleared VO bits for contiguous monotone PR by @wks in #1071
• Use live memory to estimate collection pages in mem balancer by @qinsoon in #1050
• Fix issues in sanity GC by @qinsoon in #1079

Full Changelog: v0.22.1...v0.23.0