OCaml Multicore - March 2022

Welcome to the March 2022 Multicore OCaml monthly report! This update along with the previous updates have been compiled by me, @ctk21, @kayceesrk and @shakthimaan.

We have continued steadily towards making a stable OCaml 5.0 release, as you can see from the long list of fixes later -- thank you for all your contributions! Platform configurations that were formerly supported in the 4.x branches for OpenBSD, FreeBSD, and NetBSD have now been re-enabled. ARM64 support (for macOS, Linux and the BSDs) is stable in trunk, and ARM CFI integration has been merged as a follow-up to facilitate debugging and profiling. Notably, this also includes memory model tests for ARMv8 and Power ports. The Windows mingw64 port is also working again in trunk.

An effects tutorial has also been contributed to the OCaml manual; feedback continues to be welcome even after it's merged in. As you experiment with effects, please do continue to post to this forum with questions or comments about your learnings.

The Sandmark benchmark project has added bytecode analysis to address any performance regressions. We have also been working on obtaining measurements for the compilation data points. The current-bench pipeline production deployments has significant UI changes, and now has alert notifications for the benchmark runs.

As always, the Multicore OCaml open and completed tasks are listed first, which are then followed by the ecosystem tooling projects. The Sandmark, sandmark-nightly, and current-bench project updates are finally presented for your reference.

Multicore OCaml

Open

Discussion

ocaml/ocaml#10960 Audit stdlib for mutable state

The mutable state for the Stdlib modules is actively being tracked in this issue, since the OCaml 5.0.0 implementation should be both memory and thread-safe.
ocaml/ocaml#11013 Meta-issue for OCaml 5.0 release goals

An issue tracker that contains a checklist for branching OCaml 5.0.
ocaml/ocaml#11074 OCaml 5.0 & unhandled exceptions

A question and discussion on how unhandled exceptions should be handled in OCaml 5.0.

Bug

ocaml/ocaml#10868 Fix off-by-1 bug when initializing frame hashtables

The PR for runtime/frame_descriptors.c that fixes on off-by-1 bug when initializing frame hashtables is ready to be merged.
ocaml/ocaml#11040 ThreadSanitizer issues

An issue tracker that contains list of ThreadSanitizer runs from tests/parallel execution for troubleshooting race conditions.
ocaml/ocaml#11144 Restore frame-pointers support for amd64

A work-in-progress to re-introduce the lost frame-pointers support for AMD64 architecture, since the same was partially lost with the Multicore merge.

Build

ocaml/ocaml#10315 [Build] Support for composing the compiler in a dune build

A request to use the Dune build system to build the OCaml compiler. This will be useful for Multicore OCaml ecosystem development as well.
ocaml/ocaml#10505 [RFC] Require 1003.1-2008 for libunix

A draft PR that updates the build to be compliant with The Open Group Base Specification Issue 6 and 7, IEEE Std 1003.1-2008.
ocaml/ocaml#11096 Enable native code on FreeBSD/aarch64

The configure.ac has been updated to build natively on FreeBSD/aarch64.
ocaml/ocaml#11097 Fix support for NetBSD and enable native code on NetBSD/aarch64

The support for native builds on NetBSD/aarch64 has been enabled.
ocaml/ocaml#11143 Test 32-bit build in GitHub Actions

An i386 entry in .github/workflows/build.yml has been added to test 32-bit builds with GitHub Actions.
ocaml/ocaml#11149 Make the bootstrap process repeatable

The PR enables the make bootstrap step to produce the exact same images in boot/ocamlc and boot/ocamllex, irrespective of the OS and architecture.

Enhancement

ocaml/ocaml#11057 Implement quality treatment for asynchronous actions in multicore

A work-in-progress that reimplements the caml_process_pending behaviour, and provides code improvements to the asynchronous actions in the Multicore runtime.
ocaml/ocaml#11095 Implement quality treatment for asynchronous actions in multicore (1/N)

A first set of commits as a follow-up to the Implement quality treatment for asynchronous actions in Multicore" PR.
ocaml/ocaml#11110 More ThreadSanitizer atomics and ignorelist

An ignorelist has been added to ThreadSanitizer for Field and Tag_val race conditions. A CAMLno_tsan, with a justification for no race condition for specific functions, has been added along with relaxed atomics.
ocaml/ocaml#11137 Introduce Store_tag_val(dst, val) and use it in the runtime

The runtime code does not depend on Tag_val as an lvalue, and hence Store_tag_val(dst,val) is introduced in runtime/alloc.c.
ocaml/ocaml#11138 Add C function caml_thread_has_lock

Any C thread can now call the function caml_thread_has_lock, and it returns true if the thread belongs to a domain and also holds the lock for the same.
ocaml/ocaml#11142 Gc.set now changes the minor heap size of all domains

A draft PR to adjust the semantics of Gc.set to set the minor heap size for all domains.
ocaml/ocaml#11154 Add Domain.get_name

A feature request to include get_name in the Domain module, since the API already contains a set_name.
ocaml/ocaml#11156 Post-5.00 API for changing minor heap size

The proposed suggestions for changing the minor heap size of all domains post-5.00 API.

Documentation

ocaml/ocaml#10992 OCaml multicore memory model and C (runtime, FFI, VM)

The document on the OCaml Multicore memory model and the use of the Field macro is actively being revised and updated.
ocaml/ocaml#11058 runtime/HACKING.adoc: tips on debugging the runtime

The HACKING.adoc document with information on the runtime system, and the runtime/HACKING.adoc file that explains troubleshooting is ready to be merged.
ocaml/ocaml#11093 Effects manual

The PR adds an effect handlers tutorial to the manual. The rendered web page is at https://kcsrk.info/webman/manual/effects.html.

Testing

ocaml/ocaml#10980 GitHub Actions / ocamltest / testsuite / OCaml 5

An issue tracker that contains a list of action items related to ocamltest and OCaml 5.
ocaml/ocaml#11065 Restore basic functionality to the bytecode debugger

The PR to handle stack backtraces is working now, and a separate PR will be created to handle the next instruction.
ocaml/ocaml#11121 weaklifetime_par.ml gets killed by OS's OOM-reaper on Raspberry Pi 4

A testsuite failure report on ARM64-backend on a Raspberry Pi 4 with 2GB of memory.

Performance

ocaml/ocaml#10964 Ring-buffer based runtime tracing (eventring)

The Eventring runtime tracing system designed for continuous monitoring of OCaml applications is actively being reviewed.
ocaml/ocaml#11090 Program name usability issue

A usability regression issue with Multicore runtime where top reports OCaml programs as Domain0.
ocaml/ocaml#11125 Runtime events for minor heap reservation / allocation

The runtime events that log the allocated sizes and critical sections should be emitted for the minor heap reservation and allocation functions.

Closed

Enhancement

ocaml/ocaml#10802 Use 4.12 value macros in C code

The for loop style is used for list-walking, and Val_int(0) now means an integer of value 0.
ocaml/ocaml#10958 Only rebuild flexlink.exe when sources change

The Makefile has been updated to only build flexdll/flexlink.exe when the sources have been modified.
ocaml/ocaml#10971 Means of limiting how much memory is being reserved by the runtime, so that Valgrind and AFL can be used

The max_domains value can now be set from OCAMLRUNPARAM to limit the memory usage, and to provide a good balance between usability and complexity in the implementation.
ocaml/ocaml#10991 Use zstd for CI artifacts upload and download

The upload and download time of CI artifacts are improved with the use of zstd compression.
ocaml/ocaml#11078 Relax caml_initialize assertion in the debug runtime

The assertion checks in caml_initialize are relaxed to not impede the debug runtime throughput.
ocaml/ocaml#11082 Reserve only caml_minor_heap_max_wsz * Max_domains for the minor heap

The initial minor heap size reservation is s * Max_domains, and domains can use Gc.set to increase their minor heap size beyond the reservation. The size of the reservation is always caml_minor_heap_max_wsz * Max_domains.
ocaml/ocaml#11123 Gc stats: major collections count

The use of Caml_state->stat_major_collections is removed and caml_major_cycles_completed global value is used to report statistics, as mentioned in the documentation.
ocaml/ocaml#11158 Factor out reading OCAMLTOP_INCLUDE_PATH in ocaml/ocamlnat

The identical code in ocaml and ocamlnat for parsing OCAMLTOP_INCLUDE_PATH has been refactored.

Fixes

ocaml/ocaml#11037 Assorted fixes found while restarting the Jenkins CI

The PR includes a number of fixes such as update to the Jenkins CI "main" script to better handle bytecode-only builds, updates to the test suite, configuration tweaks and changes to the runtime system.
ocaml/ocaml#11054 Respect user provided maximum stack space value, and fix debug run of tmp/stack_space.ml test

This PR honors OCAMLRUNPARAM=1 for the initial stack size, and ensures that tmc/stack_space.ml applies stack restriction during the running stage.
ocaml/ocaml#11061 dumpobj tool crashes

A fix for the segmentation fault from tools/dumpobj on a bytecode program has been merged in PR#11077.
ocaml/ocaml#11076 Adjust stack parameters for bytecode to avoid generating too many calls to caml_ensure_stack_capacity

The stack "safety margin" has been decreased to 6 and the stack threshold has been increased to 32. Most bytecode functions use no more than 32 - 6 stack slots, and this provides a quick fix for the byte code regressions.
ocaml/ocaml#11077 Fix dumpobj crash due to naked pointer comparison

The use of (==) instead of (=) in dumpobj fixes the crash in the generic comparison function that supported naked pointers.
ocaml/ocaml#11094 Domainslib producing segfaults

A patch for the segmentation fault in fiber management fixes the segmentation fault caused when using domainslib on parallel programs with Sandmark.
ocaml/ocaml#11105 Fix segfault in fiber management (issue #11094)

An integer index into an array of lists is now maintained, instead of a pointer to the cache in fiber management. This fixes the segmentation fault reported when building parallel benchmarks with domainslib in Sandmark.
ocaml/ocaml#11141 Fix 32-bit build

The runtime/gc_ctrl.c has been updated to use ARCH_INTNAT_PRINTF_FORMAT to build for 32-bit.

Testing

ocaml/ocaml#10953 ocamltest/summarize.awk not properly reporting abort failures on testsuite runs

The PR#11088 and PR#11100 have been merged to handle the failing test runs with summarize.awk.
ocaml/ocaml#11084 Disable test_cow_repeated in the lib-dynlink-private testcase when running with the debug runtime

The testsuite/tests/lib-dynlink-private/test.ml has been updated to disable test_cow_repeated with the debug runtime.
ocaml/ocaml#11004 Memory model tests

A new sub-directory in testsuite containing the memory model tests has been merged. These are useful for the ARMv8 and Power ports.
ocaml/ocaml#11088 summarize.awk: should fail when ocamltest result is not understood

The handling of unexpected results from an ocamltest run in summarize.awk have been fixed.
ocaml/ocaml#11099 ARM64 CFI support

The unwind on ARM64 for the CFI commands now work, and tests/unwind pass on both MacOS x86_64 and ARM64.
ocaml/ocaml#11124 Fix weaklifetime_par.ml

A series of fixes to fix the weaklifetime_par.ml implementation that causes test suite failures or Raspberry Pi 4.

Windows

ocaml/ocaml#10884 Fix closure marshalling from Dynlink-loaded code on Windows

The registration of empty code fragments in natdynlink has been stopped, and caml_skiplist_insert updates the data pointer if the key is a duplicate.
ocaml/ocaml#10908 Fix possible race in caml_mem_map on Windows

A race condition when trimming the memory block has been fixed, and printf debugging from the concurrent minor collector in platform.c has been cleaned up.
ocaml/ocaml#11115 Fix performance regression in systhreads on Windows

The tick thread calls caml_thread_yield on the Windows version of select which was causing performance regressions. The Sleep function is used instead and the performance differences are noticeable as shown below:
```
Test                            before/s     run1/s       run2/s
lib-threads/sieve               5.36         3.18         2.47
parallel/fib_threads            137.52       62.29        63.95
parallel/multicore_systhreads   20.2         11.88        11.08
```
ocaml/ocaml#11116 Fix tool-dumpobj test on Windows

The mingw-64 runs on Inria's CI are fixed with the update to tool-dumpobj/test.run.

Documentation

ocaml/ocaml#11008 Document and refactor the gc-stats code

The runtime/caml/gc_stats.h and runtime/gc_stat.c code have been refactored and documented.
ocaml/ocaml#11072 domain.c: document the STW synchronization code

The STW synchronization code has been documented in domain.c.
ocaml/ocaml#11073 Code comprehension: why don't STW sections keep all_domains_lock the whole time?

The STW synchronization code has been documented in domain.c in PR#11072.
ocaml/ocaml#11120 Man entries for warnings 69, 70, 71 and 72 are missing

The manual entries are listed in the output of man ocamlc, and the warnings for 69, 70, 71 and 72 have been added.
ocaml/ocaml#11122 Fix typo in Stdlib documentation comment

A typo in stdlib/stdlib.mli has been fixed.

Sundries

ocaml/ocaml#11092 Enable native code on aarch64-*-openbsd*

OCaml builds fine on OpenBSD/aarch64.
ocaml/ocaml#11112 Harden -use-runtime against spaces in paths

The PR ensures that spaces in the paths specified with -use-runtime work as expected.
ocaml/ocaml#11047 GC stats: properly orphan allocation stats

An orphaning process for allocation statistics has been implemented in this PR, where the "orphan stats" are stored in a global structure alloc_stats variable in gc_stats.c. On domain termination, the stats of the current domain are added to the "orphan stats".
ocaml/ocaml#10925 Rename symbol for Caml_state to caml_state

The Caml_state macro has been renamed to caml_state to avoid a name collision.
ocaml/ocaml#10989 Download GNU parallel directly from git

The tools/ci/appveyor/appveyor_build.sh has been updated to download GNU parallel with Git.

Ecosystem

Eio

Open

ocaml-multicore/eio#206 API request: readdir

A new API request to list the contents of the directory, since Eio.Dir.t already exists.
ocaml-multicore/eio#207 Add readdir feature

A draft PR that provides an implementation of readdir feature for Eio, and also to discuss its API.
ocaml-multicore/eio#208 Update the README to use OCaml 5.0

A suggestion to update the README to use OCaml 5.0.

Completed

ocaml-multicore/eio#205 Prepare release

The sources have been upgraded to depend on uring.0.3, and the CHANGES.md has been updated for a release.

domainslib

Open

ocaml-multicore/domainslib#68 Scope of domainslib

A feature request to have mpsc queues, concurrent hashmap and more concurrency building blocks in domainslib.
ocaml-multicore/domainslib#69 Make Chan.t and Task.promise injective

The injectivity annotations with type constructors can be usable as indexes of GADTs, in particular Effect.t.

Completed

ocaml-multicore/domainslib#65 Fix build on trunk

The Effect.eff -> Effect.t change has been updated to build for trunk, and the CI builds for 5.0.0+trunk.
ocaml-multicore/domainslib#66 Domainslib.0.4.1 build failure with OCaml 5.0.0+trunk

A newer release of domainslib.0.4.2 has been updated to build with OCaml 5.0.0+trunk.
ocaml-multicore/domainslib#67 Fix Task.parallel_for_reduce on empty loop

A corner-case for an empty loop is now correctly handled for Task.parallel_for_reduce in lib/task.ml.

Sundries

Open

ocaml-multicore/effects-examples#27 Add GitHub workflow for testing

A .github/workflows/ci.yml has been added for CI testing.
ocaml-multicore/ocaml-uring#55 FD passing sendmsg fails on WSL2

An EINVAL is returned on the latest WSL kernel when the FD passing sendmsg examples fail.

Closed

ocaml-multicore/kcas#12 Clean up dependencies

The dependencies have been removed from kcas.opam, except for dune. The Makefile has been updated, and the old ocamlbuild .mllib-file has been removed.
ocaml-multicore/retro-httpaf-bench#19 cohttp-eio: add cohttp-eio based benchmark

A cohttp_eio benchmark has been added with updates to the benchmarking scripts.
ocaml-multicore/retro-httpaf-bench#23 Update to Eio 0.2

The retro-httpaf-bench Dockerfile has been updated to use Eio 0.2.
ocaml-multicore/effects-examples#26 Port to OCaml 5.00

The effects-examples have now been ported to run on OCaml 5.0.0+trunk, without the dedicated effects syntax.

Benchmarking

Sandmark

Open

Benchmarks

ocaml-bench/sandmark#119 Additional benchmarks - hamming and soli

A draft version of the hamming.ml and soli.ml benchmarks have been added to Sandmark.
ocaml-bench/sandmark#299 Irmin 3 benchmarks

A request to update the Sandmark Irmin benchmark which replays the access patterns for Tezos.
ocaml-bench/sandmark#319 Added two serial benchmarks namely: hamming and soli with their respectively

The PR adds the Hamming and Soli sequential benchmarks to Sandmark.

CI

ocaml-bench/sandmark#275 Move from drone CI to GitHub actions

The CI jobs from .drone.yml need to be migrated to run with GitHub Actions workflow.
ocaml-bench/sandmark#316 main.yml

A new .github/workflows/main.yml GitHub Actions file has been added to run in the CI.

Dependencies

ocaml-bench/sandmark#18 js_of_ocaml fails to run on multicore

A draft PR to build js_of_ocaml in Sandmark for Multicore OCaml has been created.
ocaml-bench/sandmark#262 ocaml-migrate-parsetree.2.2.0+stock fails to compile with ocaml.5.00.0+trunk

ocaml-migrate-parsetree is no longer required for trunk with ppxlib.0.25.0~5.00preview.
ocaml-bench/sandmark#310 Remove js_of_ocaml

A work-in-progress to build js_of_caml-compiler with 5.0.0+trunk, as frama-c is not compatible with ocaml/ocaml.

Sundries

ocaml-bench/sandmark#272 Delay benchmark runs if the machine is active

A load average check for threshold 0.6 needs to be verified before running the benchmarks.
ocaml-bench/sandmark#302 Renaming suggestions for *run_config.json files

The current *run_config.json files need to be renamed as follows:
- run_config.json -> sequential.json
- multicore_parallel_run_config.json -> parallel_turing.json
- multicore_parallel_navajo_run_config.json -> parallel_navajo.json
- micro_multicore.json -> micro.json
ocaml-bench/sandmark#309 Outreachy Applicants: set-up and how-to

Sandmark is participating in the Outreachy program, and the necessary setup and how-to instructions to get started on the project have been provided.
ocaml-bench/sandmark#315 Rename Json Files

A PR to rename the current *run_config.json files to be more meaningful for their intended purpose.
ocaml-bench/sandmark#317 Add checks for loadavg

An ongoing PR to add a loadavg check to ensure that the server is not busy before actually running the benchmarks.

Closed

Bytecode

ocaml-bench/sandmark#282 Analyse Bytecode Performance

The run_config_byte.json file now allows you to run byte code version of the Sandmark benchmarks.
ocaml-bench/sandmark#298 Support to build and run benchmarks in byte mode

A run_config_byte.json file has been added to build and run the benchmarks in byte mode. You can test the same using:
```
$ USE_SYS_DUNE_HACK=1 SANDMARK_CUSTOM_NAME=5.00.0 BUILD_BENCH_TARGET=bytebench \
    RUN_CONFIG_JSON=run_config_byte.json make ocaml-versions/5.00.0+trunk.bench 
```

Notebooks

ocaml-bench/sandmark#279 Update notebooks/ To 5.00.0+trunk

The Jupyter notebooks in the notebooks/ folder have been updated to use 5.0.0+trunk.
ocaml-bench/sandmark#301 Port sandmark nightly UI to sandmark notebooks

The Sandmark-nightly UI changes have been ported to the Sandmark notebooks/ and work with 5.0.0+trunk OCaml variant.
ocaml-bench/sandmark#305 re-enable disabled benchmarks

The filter check that disabled alt-ergo, frama-c and js_of_ocaml benchmarks have been enabled in the Jupyter notebooks.

Enhancement

ocaml-bench/sandmark#274 Custom Variant Support

The feature request to specify developer branches, configure options, runtime parameters, a name for the OCaml variant, dependency package overrides, package removal list, and an expiry date until which the Sandmark nightly runs should occur has been merged to Sandmark.
ocaml-bench/sandmark#286 Update check_url and validate URL in custom.json files

The check_url target in the Makefile checks if a URL is present for each and every entry in the custom.json file, and also if the URL contains a downloadable file.
ocaml-bench/sandmark#297 Added dynamic package override and removal for Custom Support Variant

The ability to override and remove dependency packages dynamically is now supported with the Custom Support Variant feature.
ocaml-bench/sandmark#306 Update check_url and added check_jq

A check_jq functionality has been added in the Makefile to verify that the config.json files can be parsed by jq. The check_url now verifies that the provided URL is downloadable with wget.
ocaml-bench/sandmark#307 Use pristine sandmark clone for each build

A fresh clone of Sandmark is used now before each and every sandmark-nightly run, instead of relying on make clean.

Sundries

ocaml-bench/sandmark#300 Use 5.0.0+trunk name and version

Sandmark OCaml variants have been updated to use the 5.0.0+trunk name and version number.
ocaml-bench/sandmark#304 Parallel benchmarks get killed with SEGV with trunk and domainslib.0.4.2

The PR#11105 fix in the fiber management resolves the segmentation fault caused in parallel benchmarks with trunk and domainslib.0.4.2.
ocaml-bench/sandmark#308 Move nightly scripts to Sandmark

The nightly cron run scripts from sandmark-nightly have been moved to sandmark.
ocaml-bench/sandmark#312 Removed failure:ignore

The failure:ignore option has been removed from .drone.yml CI as 5.0.0+trunk builds are stable now.

Sandmark-nightly

Closed

ocaml-bench/sandmark-nightly#5 Status of disabled benchmarks

The Jupyter notebooks in Sandmark have been ported with the changes from sandmark-nightly, and the benchmarks have been enabled.
ocaml-bench/sandmark-nightly#41 Show Sandmark branch and version in the UI

The UI now shows the Sandmark branch and version number in building and running the benchmarks.
ocaml-bench/sandmark-nightly#48 Numbered list is misaligned in the home page

The list indentation has been fixed in the home page.
ocaml-bench/sandmark-nightly#49 Add Sandmark info to sandmark-nightly

The commit version and branch of Sandmark used in the sandmark-nightly runs are displayed in the UI.
ocaml-bench/sandmark-nightly#52 Resize UI to show the full OCaml variant name

The OCaml variant name width has been enlarged to show the full name in the UI.
ocaml-bench/sandmark-nightly#53 Show benchmarks in a table to read the tooltip

The selected benchmarks are displayed as a table and tooltip support has been added.

Sandmark-nightly-PR-53-tooltip|690x113

ocaml-bench/sandmark-nightly#54 Hide instrumented runtime pages

The instrumented runtime is currently not used, and hence the respective pages are hidden from the user.

current-bench

Open

ocurrent/current-bench#306 WIP ocaml compiler benchmarks

A work-in-progress, high-level issue tracker for building ocaml/ocaml compiler benchmarks, and necessary tooling with the current-bench project.
ocurrent/current-bench#318 Cobench user library

A request for a library to ease the process of creating and using benchmarks with the current-bench project.
ocurrent/current-bench#329 Use a standard record instead of a Js.object for metric data in BenchmarkData.res

A refactoring task for the metric data to use a standard record instead of a Js.object.
ocurrent/current-bench#330 Looking at the past

A list of UI changes to better view the past benchmark results for the dune team.
ocurrent/current-bench#332 Consider using time as the x-axis

A wishlist entry to visualize the graphs with time on the x-axis.
ocurrent/current-bench#333 Docker build arguments

The use of --build-args for Docker in the OCluster pipeline is required for custom Dockerfile runs with Sandmark nightly.
ocurrent/current-bench#344 Show the same sub-metric in the same color across different metric graphs

A UI enhancement to show the same colour for a sub-metric across all the graphs.

Closed

Fixes

ocurrent/current-bench#326 Frontend: Fix bug with using same x-axis for all metrics

The respective meta-data for all the commits, and for every metric in the x-axis is now correctly displayed in the UI.
ocurrent/current-bench#334 Fix CI

A minor fix in pipeline/libl/current_bench_json.ml to correctly match and resolve the benchmark name.
ocurrent/current-bench#337 Fix missing value frontend crash

A couple of fixes for Js.Obj.assign and the front-end when an overlaid metric is added to a branch.
ocurrent/current-bench#340 Missing metric indicator fixes

The BenchmarkTest.res and LineGraph.res have been fixed to handle missing metric indicator.
ocurrent/current-bench#341 frontend: Fix broken line numbers when filling in missing commits

A fix in frontend/src/AppHelpers.res to handle broken line numbers when filling missing commits.
ocurrent/current-bench#343 Fix colors changing on hiding some lines and change color palette

An aesthetic UI change on the color palette, and fix for color changes when hiding lines.
ocurrent/current-bench#345 Correctly handle carriage returns when counting line numbers

A proper way to handle \r, \r\n, and \n in the browser when showing the line numbers in the UI.

Frontend

ocurrent/current-bench#323 Allow clicking on the legend to show/hide plot lines and use more columns

The legend now uses more columns when clicking on the show/hide plot in the UI.
ocurrent/current-bench#324 Disabled worker / docker image

The frontend automatically selects the first "environment" (worker + Docker image) and the system may contain disabled ones. The environment list now filters and shows only the active entries.
ocurrent/current-bench#331 Show only workers with valid runs in workers dropdown

The workers for a specific repo_id and pull_number alone are now shown in the dropdown menu.
ocurrent/current-bench#339 frontend: Filter out values less than 0.5% of maximum

The values less than 0.5% of the maximum are now filtered out so that Array.getExn does not crash the frontend.
ocurrent/current-bench#342 Frontend: hide table comparison rows NA/NA

The NA/NA is used in the frontend when there are no branch forks to compare in the graphs.

Sundries

ocurrent/current-bench#327 Slack

The debug logs from benchmark runs can now be sent to Slack for alert notification.

Current-bench-PR-327-alert|690x301

ocurrent/current-bench#328 Add a Cobench client library for pushing results with the HTTP API

The Irmin benchmark monthly results need to be uploaded to current-bench, and hence a Cobench client library has been created to be used with the HTTP API.
ocurrent/current-bench#336 Docker build arguments

The environment/*.conf file now supports an optional build_args setting that can be used to pass environment variables to make bench. This is useful for sandmark-nightly as well for cron-like scheduling of fast and slow benchmarks.
```
{
"repositories": [
  {
    "name": "local/local",
    "worker": "autumn",
    "build_args": ["FOO=42"]
  },
```
ocurrent/current-bench#338 Use latest OCurrent for logs line number links

The ocurrent-bench.opam and pipeline/pipeline.opam files have been updated to use the latest OCurrent version.

We would like to thank all the OCaml users, developers and contributors in the community for their continued support to the project.

Acronyms

AFL: American Fuzzy Lop
AMD: Advanced Micro Devices
API: Application Programming Interface
ARM: Advanced RISC Machines
AWK: Aho Weinberger Kernighan
BSD: Berkeley Software Distribution
CFI: Call Frame Information
CI: Continuous Integration
FD: File Descriptor
FFI: Foreign Function Interface
GADT: Generalized Algebraic Data Type
GC: Garbage Collector
GNU: GNU's Not Unix
HTTP: Hypertext Transfer Protocol
IEEE: Institute of Electrical and Electronics Engineers
JSON: JavaScript Object Notation
MD: Markdown
OOM: Out Of Memory
OPAM: OCaml Package Manager
OS: Operating System
PR: Pull Request
RFC: Request For Comments
STW: Stop The World
UI: User Interface
URL: Uniform Resource Locator
VM: Virtual Machine
WSL: Windows Subsystem for Linux