v2025.07

Makefile

• add TAG variable for distinguished build directory names
• new targets for generating disassembly using objdump -d
• templatize recipes for the specific tests in /ext

Test changes

multiple tests

• include/atomics.h: fix asm positional constraints

pthread_mutex_lock and pthread_mutex_trylock

• new tests

tbb_spin_rw_mutex

• fix volatile cast of state variable
• support USE_BUILTIN on aarch64
• use a CPU list instead of bitmask for pure readers to allow more than 64 CPUs to be specified
• use the lock pointer from the test harness instead of a global state variable for improved reproducibility
• parameterize pause count for atomic_backoff_pause
• initialize per-thread counter to a unique value so that non-pure readers do not try to write at the same time

Lockhammer test harness

Command line flags

• -T duration_sec: renamed from -D duration_sec
• -T tag: stores a tag string in the results JSON
• -v -v: increase verbosity to more verbose
• -o pinorder: support CPU ranges, e.g. -o 10-20:2 for even-numbered CPUs in CPU10-20, inclusive
• -i interleave: remove, and make interleave a subparameter to -t threads[:interleave]
• -h: print help only if -h is used

Measurement

• always measure the TSC frequency on x86
• blackhole iterations chosen from median of 5 searches
• add lock_acquire and lock_release callsite labels in disassembly

Reporting/JSON

• add a test_type_name string for test-specific variant
• store cpuorder_filename and pinorder_string in the JSON
• store the -T tag in the JSON
• store the -o pinorder and -t threads[:interleave] argument as pinorder_string in the JSON

Support scripts

view-results-json.sh

• handle missing keys
• handle non-numerical results, isnormal when using older jq versions
• show the new pinorder/num_threads string
• add -T tag to select results only of that tag
• add -a additional_key flag to also show data from that key

run-tests.sh

• show summary of configuration, and require -n or -N to proceed
• estimate runtime based on tests to run
• add flags to override the built-in lists of permuted parameters
• add -T tag to run only from the build dirs containing the tag
• add -- support to pass additional flags directly to the lh_$test program
• add -M hugepage_size to specify the hugepage size to use instead of the default 1GB
• rename the -T duration_sec flag to -D duration_sec

json-to-command.sh

• new; reconstructs the lh_$testname command line from a JSON's measurement record

v2025.05

Improve run-to-run reproducibility

• add time-based measurement mode so that no threads finish early to let the remaining threads have less competition
• reuse the same physical address run-to-run by allocating the lock memory from a persistent hugetlb page
• detect cpufreq driver and governors that could affect performance under load
• improve thread cleanup in case of crash or test timeout

Usability for scaling studies

• any-cpu pinorder assignment; CPU0 does not need to be used explicitly/implicitly
• multiple measurements per run, permuting iterations, critical/parallel durations, and num_threads/pinorders
• results capture to JSON, with a script provided to display/compare multiple JSONs
• per-thread fairness and execution duration data
• aarch64: runtime support to disable LSE in outline atomics

Improve maintainability

• separate compilation of measurement code so that the test harness does not use the same target optimizations as the lock implementation; faster compilation
• rewritten Makefile with automatic dependencies, separate build directories, parallel make, and phony targets for building all variants in one make command
• implement a __cpu_relax() macro to centralize its implementation across tests
• long options support and help screen
• vim modelines for per-file whitespace type and indentation spacing

Test-specific changes

• osq_lock: support smp_cond_load_relaxed macro, provide more control over relax and backoff durations
• jvm_objectmonitor: more accurately represent jdk-9, fix a use-after-free, reduce the presence of malloc
• cas_event_mutex: allow use of __atomic intrinsic on aarch64
• various: quell compiler warnings, support compilation with clang, document limitations/TODO

v1.0

This never had a version numbering before, so I'm tagging what was here as v1.0.