core 111.06-rc1

# 111.06.00

## async_extra

- Added `?on_wouldblock:(unit -> unit)` callback to
  `Udp.recvmmsg_loop` and `recvmmsg_no_sources_loop`.
- For functions that create `Rpc` connections, added optional
  arguments: `?max_message_size:int` and
  `?handshake_timeout:Time.Span.t`.

  These arguments were already available to `Connection.create`, but
  are now uniformly available to all functions that create
  connections.

## async_kernel

- Improved the performance of `Pipe.filter_map` by using batching.

## async_ssl

Initial release

## async_unix

- In the `Busy_pollers.t` record, made the `kernel_scheduler` field be
  `sexp_opaque`.

  Did this so that one doesn't get two copies of the kernel scheduler
  in sexps of the scheduler, which already has its own
  `kernel_scheduler` field.

## core

- Added inline benchmarks for =Iobuf= and =Time=.

  Hera are some of the results from the new benchmarks, with some
  indexed tests dropped.

  | Name                                 | Time/Run | mWd/Run | Percentage |
  |--------------------------------------|----------|---------|------------|
  | [time.ml:Time] Time.to_string        | 848.74ns | 249.98w |    100.00% |
  | [time.ml:Time] Time.to_ofday         |  59.66ns |  38.00w |      7.03% |
  | [time.ml:Time] Time.now              |  39.78ns |   2.00w |      4.69% |
  | [time.ml:Time] Time.Zone.find_office |  83.64ns |   4.00w |      9.85% |
  | [time.ml:Time] Time.Span.of_hr       |   3.71ns |   2.00w |      0.44% |
  | [time.ml:Time] Time.Span.of_min      |   3.69ns |   2.00w |      0.44% |
  | [time.ml:Time] Time.Span.of_sec      |   2.72ns |         |      0.32% |
  | [time.ml:Time] Time.Span.of_ms       |   6.02ns |   2.00w |      0.71% |
  | [time.ml:Time] Time.Span.of_ns       |   5.98ns |   2.00w |      0.71% |

  | Name                                     | Time/Run | Percentage |
  |------------------------------------------|----------|------------|
  | [iobuf.ml:Blit tests] functor blit:5     |  15.53ns |      7.66% |
  | [iobuf.ml:Poke tests] char:0             |   4.11ns |      2.03% |
  | [iobuf.ml:Poke tests] uint8:0            |   5.35ns |      2.64% |
  | [iobuf.ml:Poke tests] int8:0             |   4.59ns |      2.26% |
  | [iobuf.ml:Poke tests] int16_be:0         |   5.19ns |      2.56% |
  | [iobuf.ml:Poke tests] int16_le:0         |   5.14ns |      2.53% |
  | [iobuf.ml:Poke tests] uint16_be:0        |   5.11ns |      2.52% |
  | [iobuf.ml:Poke tests] uint16_le:0        |   5.12ns |      2.53% |
  | [iobuf.ml:Poke tests] int32_be:0         |   5.17ns |      2.55% |
  | [iobuf.ml:Poke tests] int32_le:0         |   4.91ns |      2.42% |
  | [iobuf.ml:Poke tests] uint32_be:0        |   5.73ns |      2.83% |
  | [iobuf.ml:Poke tests] uint32_le:0        |   5.74ns |      2.83% |
  | [iobuf.ml:Poke tests] int64_be:0         |   5.33ns |      2.63% |
  | [iobuf.ml:Poke tests] int64_le:0         |   4.93ns |      2.43% |
  | [iobuf.ml:Peek tests] char:0             |   5.50ns |      2.71% |
  | [iobuf.ml:Peek tests] uint8:0            |   4.68ns |      2.31% |
  | [iobuf.ml:Peek tests] int8:0             |   4.91ns |      2.42% |
  | [iobuf.ml:Peek tests] int16_be:0         |   5.19ns |      2.56% |
  | [iobuf.ml:Peek tests] int16_le:0         |   4.90ns |      2.42% |
  | [iobuf.ml:Peek tests] uint16_be:0        |   5.17ns |      2.55% |
  | [iobuf.ml:Peek tests] uint16_le:0        |   5.10ns |      2.51% |
  | [iobuf.ml:Peek tests] int32_be:0         |   5.17ns |      2.55% |
  | [iobuf.ml:Peek tests] int32_le:0         |   4.92ns |      2.42% |
  | [iobuf.ml:Peek tests] uint32_be:0        |   5.45ns |      2.69% |
  | [iobuf.ml:Peek tests] uint32_le:0        |   5.46ns |      2.69% |
  | [iobuf.ml:Peek tests] int64_be:0         |   6.61ns |      3.26% |
  | [iobuf.ml:Peek tests] int64_le:0         |   6.31ns |      3.11% |
- Re-implemented `Thread_safe_queue` to improve performance and reduce
  allocation.

  The new implementation requires 3 words per element, down from the 7
  words required by the old implementation.

  The new implementation pools elements so that they can be reused, so
  there is no allocation in steady-state use.

  The new implementation has `dequeue_exn` rather than `dequeue`, so
  that one can dequeue without allocating 2 words.

  Eliminated `create'`.  One should just use `create` and explicit calls
  to `enqueue` and `dequeue_exn`.

  Eliminated `dequeue_until_empty`.  One should use an explicit while
  loop guarded by `length` and using `dequeue_exn`.

  Moved `Thread_safe_queue` from `Core_kernel` to `Core`, since it's
  thread related.

  All in, there is now no allocation in a steady-state usage of
  enqueueing and dequeueing elements, as opposed to 9 words per
  `enqueue+dequeue` in the old implementation.  This reduces the cost
  from `enqueue+dequeue` taking 166-216ns to `enqueue+dequeue_exn`
  taking 48-82ns (plus eliminating gc impacts).  Here are some `BENCH`
  results, the first table being the old implementation, and the
  second table the new.

  | Name                                                       | Time/Run | mWd/Run | mjWd/Run |
  |------------------------------------------------------------|----------|---------|----------|
  | [thread_safe_queue.ml] enqueue + dequeue of immediate      | 183.89ns |   9.00w |    7.02w |
  | [thread_safe_queue.ml] enqueue + dequeue of young object   | 216.69ns |  11.00w |    9.01w |
  | [thread_safe_queue.ml] enqueue + dequeue_exn of old object | 166.75ns |   9.00w |    7.02w |

  | Name                                                         | Time/Run | mWd/Run |
  |--------------------------------------------------------------|----------|---------|
  | [thread_safe_queue.ml] enqueue + dequeue_exn of immediate    |  48.20ns |         |
  | [thread_safe_queue.ml] enqueue + dequeue_exn of young object |  81.96ns |   2.00w |
  | [thread_safe_queue.ml] enqueue + dequeue_exn of old object   |  48.30ns |         |
- Changed `{Bigstring,Iobuf}.recvmmsg_assume_fd_is_nonblocking`, when
  no message is available, to return a negative number rather than
  raise.

  This was done for performance reasons, because raising an exception
  is expensive, due to the stashing of the backtrace and the string
  creation.
- Added `Iobuf.unsafe_resize`.
- Changed `Bigstring.blit` so that it doesn't release the OCaml lock
  on `map_file` bigstrings.

  The old behavior of releasing the lock for blits of (small)
  bigstrings involving mmapped files was problematic and inconsistent.
  Its cost is high, and fundamentally any access to a mapped bigstring
  could cause some level of blocking.
- Added time-related `Arg_type.t` values to `Command.Spec`.
- Added module `Type_immediacy`, which has witnesses that express
  whether a type's values are always, sometimes, or never immediate.

  This code used to be in the `Typerep_immediate` library in typerep.

## core_kernel

- Added inline benchmarks for `Array`

  Hera are some of the results from the new benchmarks, with some
  indexed tests dropped.

  | Name                                                |    Time/Run | mWd/Run |  mjWd/Run |
  |-----------------------------------------------------|-------------|---------|-----------|
  | [core_array.ml:Alloc] create:0                      |     13.65ns |         |           |
  | [core_array.ml:Alloc] create:100                    |     99.83ns | 101.00w |           |
  | [core_array.ml:Alloc] create:255                    |    201.32ns | 256.00w |           |
  | [core_array.ml:Alloc] create:256                    |  1_432.43ns |         |   257.00w |
  | [core_array.ml:Alloc] create:1000                   |  5_605.58ns |         | 1_001.01w |
  | [core_array.ml:Blit.Poly] blit (tuple):10           |     87.10ns |         |           |
  | [core_array.ml:Blit.Poly] blito (tuple):10          |    112.14ns |   2.00w |           |
  | [core_array.ml:Blit.Poly] blit (int):10             |     85.25ns |         |           |
  | [core_array.ml:Blit.Poly] blito (int):10            |    107.23ns |   2.00w |           |
  | [core_array.ml:Blit.Poly] blit (float):10           |     84.71ns |         |           |
  | [core_array.ml:Blit.Poly] blito (float):10          |     86.71ns |   2.00w |           |
  | [core_array.ml:Blit.Int] blit:10                    |     19.77ns |         |           |
  | [core_array.ml:Blit.Int] blito:10                   |     23.54ns |   2.00w |           |
  | [core_array.ml:Blit.Float] blit:10                  |     19.87ns |         |           |
  | [core_array.ml:Blit.Float] blito:10                 |     24.12ns |   2.00w |           |
  | [core_array.ml:Is empty] Polymorphic '='            |     18.21ns |         |           |
  | [core_array.ml:Is empty] Array.equal                |      8.08ns |   6.00w |           |
  | [core_array.ml:Is empty] phys_equal                 |      2.98ns |         |           |
  | [core_array.ml:Is empty] Array.is_empty (empty)     |      2.98ns |         |           |
  | [core_array.ml:Is empty] Array.is_empty (non-empty) |      3.00ns |         |           |
- Moved `Thread_safe_queue` to core
- Generalized the type of `Exn.handle_uncaught_and_exit` to `(unit ->
  'a) -> 'a`.

  In the case where `handle_uncaught_and_exit` succeeds, it can return
  the value of the supplied function.

  It's type had been:

  ```ocaml
  val handle_uncaught_and_exit : (unit -> never_returns) -> never_returns
  ```
- Added `Int.round*` functions for rounding to a multiple of another
  int.

  ```ocaml
  val round : ?dir:[ `Zero | `Nearest | `Up | `Down ] -> t -> to_multiple_of:t -> t

  val round_towards_zero : t -> to_multiple_of:t -> t
  val round_down         : t -> to_multiple_of:t -> t
  val round_up           : t -> to_multiple_of:t -> t
  val round_nearest      : t -> to_multiple_of:t -> t
  ```

  These functions were added to `Int_intf.S`, implemented by `Int`,
  `Nativeint`, `Int32`, and `Int64`.

  Various int modules were also lightly refactored to make it easier
  in the future to implement common operators available for all
  modules implementing the int interface via a functor to share the
  code.

## jenga

- Improved the error message when the same library is defined multiple
  times.
- Fixed an issue where jenga sometimes would sometimes complain about
  a self cycle when `foo.ml` uses a module `Foo`.
- With `-no-notifiers`, jenga doesn't use `inotify` to watch for file
  changes.  This is useful for linting `jengaroot.ml`.
- Allowed writing jenga rules which restrict dependencies from an
  initial conservative approximation to a more accurate set discovered
  after an action is run

## re2

- Added `Re2.Std`, so that one should now use `Re2` via `module Re2 =
  Re2.Std.Re2`.

  At some future date, we will rename the `Regex` module to
  `Re2_internal` to force the stragglers to update to the new
  convention.

## typerep

- Renamed `Typerep` libraries for more consistency with the rest of
  the framework.

  ```ocaml
  Typerep_kernel --> Typerep_lib
  Typerep_core   --> Typerep_extended
  Typereplib     --> Typerep_experimental
  ```