Known issues in MPS release 1.116.0

This list may include some issues incorrectly, because "p4 fixes -i" does not report a fix for a version branch if the files changed by the fix were deleted on the masters before the version branch was taken.

Job Priority Title
job003499 critical The MPS issues list looks scary
job004165 critical MPS is to be BSD 2-clause licenced.
job000546 essential MPS docs say P4DTI instead of MPS
job000602 essential Mac OS X 10.2 build fails because "cabs" is already defined
job000668 essential Build procedure uses p4 counter change which is unsafe
job000973 essential MPS doesn't compile under Mac OS X 10.3.4
job001155 essential full collects cause gigantic ramps
job001367 essential MPS lacks walkthrough example code (aka "hello-world") for beginners
job003434 essential Incorrect glossary link from "committed" to "mapping"
job003469 essential CET can't safely make use of the top 2GiB of memory on 32-bit Windows
job003486 essential mv2test failure
job003674 essential Hysteresis overwhelmed by allocation
job004019 essential Can't handle access violation if arena is locked
job004027 essential Memory corruption due to multiple arenas in multiple threads
job004054 essential Can't destroy arena with outstanding finalization messages
job004061 essential Manual does not build with Sphinx 1.6
job004076 essential MPS does not compile with GCC 7
job004086 essential Assertion failure in amssshe
job004108 essential MPS does not build with Xcode 10.0
job004113 essential MPS does not compile with GCC 7.3
job004156 essential MPS does not compile with GCC 8.3
job004158 essential Register scanning approach is not reliable
job004162 essential MPS does not compile with Clang 6.0.0
job004166 essential MPS Contributing agreement requires review and update
job000537 optional Many design documents missing
job000538 optional Project documents are poorly formatted
job000549 optional Blackening an AMS segment can break
job001092 optional MPS is not integrated with public cool projects.
job001150 optional MPS doesn't provide enough feedback information about what it is doing or what it has done
job001151 optional Format methods can't look at other data
job001152 optional The MPS can't be used to simulate a smaller machine
job001659 optional Culprit analysis is too hard.
job001666 optional No guarantee that all weak references to an object die together.
job001707 optional VM Arena never shrinks a generation zone set preferences.
job003352 optional Instruction emulation not supported on OS X or x86-64
job003384 optional Collector goes mad when low on address space
job003387 optional Multiple arenas can corrupt telemetry stream
job003388 optional telemetry system API can corrupt telemetry stream
job003439 optional MPS is too hard to use
job003455 optional Frequent ramps can mess up the ramping algorithm and cause performance problems
job003477 optional MPS is hard to build and debug on Windows
job003505 optional MPS incurs large overhead on barrier hits
job003513 optional Arena extension callbacks are undocumented
job003523 optional Accessing to weak tables on 64-bit causes them to be scanned.
job003525 optional Pointers from MPS stack pin down user objects
job003532 optional MPS kit fails to install shared libraries
job003644 optional Reserve/commit protocol does not cope with exceptions
job003683 optional Epoch number can wrap around on 32-bit platforms
job003755 optional Telemetry tools not regularly tested
job003764 optional Scanning rate is way too high
job003780 optional No test case for register scanning
job003783 optional ChainCondemnAuto condemns too many generations
job003790 optional Segment descriptors could be more efficiently managed
job003796 optional White segment lookup is slow
job003797 optional AMC space is lost to pinning
job003798 optional Tract tables are inflexible
job003799 optional Incrementally collecting the nursery may waste time
job003813 optional TraceReclaim looks at every segment
job003815 optional Freeing a page never destroys a chunk
job003832 optional CVM memory debugging may be redundant
job003841 optional Segs are not Exposed when AMSBlacken calls amsIterate
job003848 optional Access violation in gcbench on Windows
job003917 optional Clear x86 direction flag in exception handler
job003921 optional Write barrier may be harmful to performance
job003929 optional mps_arena_step uses poor estimate of collection time
job003932 optional Allocation frame documentation is unclear
job003942 optional Possible hang in steptest
job003944 optional Arena allocation policy may allocate in blacklisted zone
job003953 optional Definalization doesn't scale
job003955 optional No regression test for job003898
job003957 optional MutatorFaultContext interface is inconsistent and incomplete
job003960 optional No way to get live information about the behaviour of the MPS
job003963 optional Address-based hash table design is not stress-tested
job003969 optional Event clock implementation may not be reliable
job003970 optional The MPS can't scan in parallel with the mutator
job003974 optional StackContext and MutatorContext could be unified
job003976 optional Can't scan parts of segments allocated by buffers
job003977 optional We maintain redundant NMAKE files
job003979 optional Forwarding unnecessarily lowers the read barrier
job003980 optional Branching tool does not distinguish between private and public Git mappings
job003981 optional MPS does not benefit from huge TLB entries
job003984 optional Calling mps_clock frequently is bad for performance
job003987 optional Emergency collection is not documented
job003988 optional No continuous integration test for 32-bit MPS on Linux and OS X
job003989 optional On Windows, pause times are measured using clock(), which is wall-clock time
job003992 optional MAX_SIZE means different things to MV and MVT pools
job003995 optional MPS doesn't support debugging APs
job003999 optional Manually managed address space is only returned to the operating system via a trace
job004001 optional No representation of the set of generations condemned by a trace
job004002 optional Can't implement incremental condemn
job004004 optional mps_arena_pause_time and mps_arena_pause_time_set are not covered
job004008 optional AMSSegMerge loses buffer on high segment
job004010 optional No check that collecting a generation reduces its "new size" to zero
job004016 optional AMC pool may scan parts buffered segments many times
job004022 optional Mutator is suspended while the foundation is discovered
job004023 optional Summary-based write barrier invariant won't cope with pre-flip scanning
job004030 optional Failed shield assertion in finalization tests with deep checking
job004035 optional Thread roots not suitable for user-level threads
job004048 optional MMQA test cases fail on w3i6mv
job004055 optional Documentation for mps_root_create_area_tagged is incorrect
job004056 optional lockEnsureGlobalLock is not thread-safe on Windows
job004062 optional fork() unsupported on FreeBSD, Linux and macOS
job004065 optional Scan area functions not flexible enough
job004070 optional LO and AWL pools fail to detect invalid exact references
job004072 optional MRG segments needlessly set the write barrier
job004074 optional mps_definalize might not work
job004082 optional ztfm.c does not compile with Microsoft Visual C 2015
job004084 optional MMQA test function/232.c crashes
job004085 optional MPS doesn't cooperate well with other SEGV handlers
job004090 optional Walking the roots means you can't walk the formatted objects
job004093 optional Predicted mortality is bogus for collection of the world
job004094 optional Trace mortality prediction is bogus
job004096 optional MMQA fails to handle assertion failures
job004097 optional MMQA ignores assertions in tests with OUTPUT_SPEC
job004098 optional Use of clock() is not fork-safe
job004099 optional Monitor not usable for long-running processes
job004100 optional Inconsistent linearization of event times
job004102 optional arenaFreeLandInsertSteal might pass an empty range to LandInsert
job004105 optional Time and space overheads are high
job004161 optional tagtest fails on lii6gc
job004163 optional Scheme example does not build with Clang 11
job000543 nice No MPS programmer's guide
job000548 nice AMS grain colour doesn't agree with design doc
job001357 nice Configura cannot use Win32 fibers
job001369 nice MPS proc/release-build omits step: update main MPS index page
job001571 nice MPS multiple traces would not work
job001676 nice AMC does not implement weakness in emergency fixing.
job001708 nice VM Arena's segment placement policy could be improved.
job001709 nice VM Arena uses up zones too quickly.
job001715 nice MPS fails to lower barrier when hit: multiple hits cause slowdown (CONJECTURE)
job001789 nice MPS auto_header format is not tested by main test files
job003324 nice Manual contains little about performance of interface
job003325 nice Purpose of the "class" method of an object format is unclear
job003328 nice Possible improvement to reserve/commit protocol
job003357 nice AWL is awkward to use
job003374 nice No documentation about low memory situations
job003448 nice mps_arena_vm_growth is not documented
job003482 nice Test suite doesn't test error paths
job003490 nice Assertion failure in MRGDescribe
job003493 nice No recovery mode after assertion failure
job003508 nice Little in manual about in-band headers
job003515 nice Can't collect diverse MPS messages in order
job003632 nice Difficult to integrate with application that has non-atomic updates
job003653 nice Scanner makes no use of __builtin_prefetch
job003660 nice Asssertion "ring->next != NULL" in ztfm test
job003671 nice Non-moving pools don't make best use of zones
job003719 nice Hard to test and debug threading behaviour
job003758 nice The MPS does not build with gcc -Wconversion
job003763 nice No easy way to automatically clear freed memory
job003766 nice Splitting and merging complicates writing new seg classes
job003770 nice MPS does not compile from C++
job003781 nice No automated performance test
job003786 nice No automated test of the event subsystem
job003789 nice MPS does not try collecting when out of memory
job003791 nice Can't set the rank on an AMC/AMCZ allocation point
job003792 nice AMS and AWL don't update summaries of condemned segments
job003795 nice Arena extensions are not adaptive
job003802 nice Manual unclear about exact collection
job003803 nice Hard to discover roots
job003805 nice Bit table scanning is unoptimized
job003816 nice Can't specify generation per allocation point
job003837 nice No control over which objects are "large"
job003838 nice MVT uses segments unnecessarily
job003839 nice No benchmarks for space performance
job003842 nice Missing dependencies in nmake build system
job003847 nice Allocation clock inconsistency in handling of AMC segment padding
job003852 nice No heap consistency checker
job003858 nice Allocating segments in control pool has a bad complexity
job003859 nice Assertion failures in amcssth
job003864 nice Uncollected finalization messages lead to retention
job003881 nice SNC never returns memory to the arena
job003894 nice Intrinsic functions not used on Windows
job003895 nice No interface to logging control
job003905 nice Can't build the MPS in parallel
job003919 nice No interface for getting bytes allocated
job003924 nice Unnecessary allocation during arena creation
job003928 nice VM arena uses two VMs when one might do
job003941 nice Configuration parameters are uncommented
job003943 nice No consistent way to discover arena configuration
job003945 nice Easy to mistakenly omit to enable finalization messages
job003947 nice Allocation frame protocol not safe for general pools
job003950 nice Manual not compatible with Sphinx 1.3.1
job003978 nice Too hard to experiment with different MPS parameters
job003990 nice MPS doesn't notice if clients write scanners that don't check error codes
job003991 nice No validation tests for client formats.
job004005 nice Destroying an automatically managed pool does not check that the arena is parked
job004009 nice Can't split a segment if buffer is above the split point
job004024 nice Accounting overheads are too high on mark & sweep pools
job004025 nice Duplicate code between pool classes
job004047 nice Inconvenient to run multiple MMQA testsets
job004057 nice Warning pragmas are not localised around the bad cases
job004063 nice Easy to miss mps_addr_pool
job004066 nice Thread-handling functions could do more checking
job004067 nice Telemetry interacts poorly with fork
job004068 nice Duplicate thread-management code
job004069 nice macOS thread registration guard is ineffective and unnecessary
job004073 nice wasMarked protocol is unnecessarily complex
job004077 nice No test cases for bogus arguments to mps_finalize
job004078 nice Typedefs use int when unsigned would be better
job004080 nice Telemetry output not appropriate for interactive use
job004081 nice Event descriptions are in a mess
job004083 nice ChainCreate calls ControlAlloc twice
job004087 nice GenDescCondemned should check that some bytes were condemned
job004088 nice Can't destroy an allocation point with a reserve
job004089 nice No smoke test coverage of mps_arena_roots_walk
job004091 nice No support for saving and restoring automatically managed memory
job004092 nice MMQA test cases fail on 32-bit platforms
job004095 nice No need for two classes of MRG segment
job004101 nice Plain CBS doesn't work
job004103 nice No smoke test coverage of mapping failure in pagesMarkAllocated
job004104 nice fotest fails with "arena commit limit exceeded"
job004106 nice mps_collections doesn't count all collections.
job004107 nice Debugging chapter is out of date
job004109 nice Hash table advice does not mention sets
job004142 nice MPS sources contain links to private documents
job004147 nice MMQA test function/167.c fails on w3i6mv
job004148 nice MMQA relies on deprecated API mps_tramp
job004149 nice MMQA tests conerr/60.c to conerr/68.c fail on w3i6mv
job004164 nice Warning from GCC