Add Picos_std_sync.Queue

Author: polytypic

Diff for: bench/bench_queue.ml

@@ -0,0 +1,86 @@
+open Multicore_bench
+open Picos_std_sync
+
+let run_one_domain ~budgetf ?(n_msgs = 50 * Util.iter_factor) () =
+  let t = Queue.create ~padded:true () in
+
+  let op push =
+    if push then Queue.push t 101
+    else match Queue.pop_exn t with _ -> () | exception Queue.Empty -> ()
+  in
+
+  let init _ =
+    assert (
+      match Queue.pop_exn t with _ -> false | exception Queue.Empty -> true);
+    Util.generate_push_and_pop_sequence n_msgs
+  in
+  let work _ bits = Util.Bits.iter op bits in
+
+  Times.record ~budgetf ~n_domains:1 ~init ~work ()
+  |> Times.to_thruput_metrics ~n:n_msgs ~singular:"message" ~config:"one domain"
+
+let run_one ~budgetf ~n_adders ~n_takers () =
+  let n_domains = n_adders + n_takers in
+
+  let n_msgs = 50 * Util.iter_factor in
+
+  let t = Queue.create ~padded:true () in
+
+  let n_msgs_to_add = Countdown.create ~n_domains:n_adders () in
+  let n_msgs_to_take = Countdown.create ~n_domains:n_takers () in
+
+  let init _ =
+    assert (
+      match Queue.pop_exn t with _ -> false | exception Queue.Empty -> true);
+    Countdown.non_atomic_set n_msgs_to_add n_msgs;
+    Countdown.non_atomic_set n_msgs_to_take n_msgs
+  in
+  let work i () =
+    if i < n_adders then
+      let rec work () =
+        let n = Countdown.alloc n_msgs_to_add ~domain_index:i ~batch:1000 in
+        if 0 < n then begin
+          for i = 1 to n do
+            Queue.push t i
+          done;
+          work ()
+        end
+      in
+      work ()
+    else
+      let i = i - n_adders in
+      let rec work () =
+        let n = Countdown.alloc n_msgs_to_take ~domain_index:i ~batch:1000 in
+        if 0 < n then
+          let rec loop n =
+            if 0 < n then begin
+              match Queue.pop_exn t with
+              | _ -> loop (n - 1)
+              | exception Queue.Empty ->
+                  Backoff.once Backoff.default |> ignore;
+                  loop n
+            end
+            else work ()
+          in
+          loop n
+      in
+      work ()
+  in
+
+  let config =
+    let format role n =
+      Printf.sprintf "%d %s%s" n role (if n = 1 then "" else "s")
+    in
+    Printf.sprintf "%s, %s"
+      (format "nb adder" n_adders)
+      (format "nb taker" n_takers)
+  in
+  Times.record ~budgetf ~n_domains ~init ~work ()
+  |> Times.to_thruput_metrics ~n:n_msgs ~singular:"message" ~config
+
+let run_suite ~budgetf =
+  run_one_domain ~budgetf ()
+  @ (Util.cross [ 1; 2; 4 ] [ 1; 2; 4 ]
+    |> List.concat_map @@ fun (n_adders, n_takers) ->
+       if Picos_domain.recommended_domain_count () < n_adders + n_takers then []
+       else run_one ~budgetf ~n_adders ~n_takers ())

Diff for: bench/dune

@@ -11,6 +11,7 @@
    (run %{test} -brief "Picos Mutex")
    (run %{test} -brief "Picos Semaphore")
    (run %{test} -brief "Picos Spawn")
+   (run %{test} -brief "Picos Queue")
    (run %{test} -brief "Picos Yield")
    (run %{test} -brief "Picos Cancel_after with Picos_select")
    (run %{test} -brief "Ref with Picos_sync.Mutex")

Diff for: bench/main.ml

@@ -9,6 +9,7 @@ let benchmarks =
     ("Picos DLS", Bench_dls.run_suite);
     ("Picos Mutex", Bench_mutex.run_suite);
     ("Picos Semaphore", Bench_semaphore.run_suite);
+    ("Picos Queue", Bench_queue.run_suite);
     ("Picos Spawn", Bench_spawn.run_suite);
     ("Picos Yield", Bench_yield.run_suite);
     ("Picos Cancel_after with Picos_select", Bench_cancel_after.run_suite);

Diff for: lib/picos_std.sync/picos_std_sync.ml

@@ -4,4 +4,5 @@ module Semaphore = Semaphore
 module Lazy = Lazy
 module Latch = Latch
 module Ivar = Ivar
+module Queue = Queue
 module Stream = Stream

Diff for: lib/picos_std.sync/picos_std_sync.mli

@@ -351,6 +351,81 @@ module Ivar : sig
       variable has either been assigned a value or has been poisoned. *)
 end
 
+module Queue : sig
+  (** A lock-free multi-producer, multi-consumer queue. *)
+
+  (** {1 API} *)
+
+  type !'a t
+  (** A multi-producer, multi-consumer queue. *)
+
+  val create : ?padded:bool -> unit -> 'a t
+  (** [create ()] returns a new empty multi-producer, multi-consumer queue. *)
+
+  val push : 'a t -> 'a -> unit
+  (** [push queue value] adds the [value] to the tail of the [queue]. *)
+
+  val push_head : 'a t -> 'a -> unit
+  (** [push_head queue value] adds the [value] to the head of the [queue]. *)
+
+  exception Empty
+  (** Raised by {!pop_exn} in case it finds the queue empty. *)
+
+  val pop_exn : 'a t -> 'a
+  (** [pop_exn queue] tries to remove the value at the head of the [queue].
+      Returns the removed value or raises {!Empty} in case the queue was empty.
+
+      @raise Empty in case the queue was empty. *)
+
+  val pop_opt : 'a t -> 'a option
+  (** [pop_opt queue] tries to remove the value at the head of the [queue].
+      Returns the removed value or [None] in case the queue was empty. *)
+
+  val pop : 'a t -> 'a
+  (** [pop queue] waits until the queue is not empty, removes the value at the
+      head of the [queue], and returns it. *)
+
+  val length : 'a t -> int
+  (** [length queue] returns the length or the number of values in the
+      [queue]. *)
+
+  val is_empty : 'a t -> bool
+  (** [is_empty queue] is equivalent to {{!length} [length queue = 0]}. *)
+
+  (** {1 Examples}
+
+      An example top-level session:
+      {[
+        # let q : int Queue.t =
+            Queue.create ()
+        val q : int Picos_std_sync.Queue.t = <abstr>
+
+        # Queue.push q 42
+        - : unit = ()
+
+        # Queue.push_head q 76
+        - : unit = ()
+
+        # Queue.length q
+        - : int = 2
+
+        # Queue.push q 101
+        - : unit = ()
+
+        # Queue.pop_exn q
+        - : int = 76
+
+        # Queue.pop_exn q
+        - : int = 42
+
+        # Queue.pop_exn q
+        - : int = 101
+
+        # Queue.pop_exn q
+        Exception: Picos_std_sync__Queue.Empty.
+      ]} *)
+end
+
 module Stream : sig
   (** A lock-free, poisonable, many-to-many, stream.
 
@@ -423,6 +498,8 @@ end
         val push : 'a t -> 'a -> unit
         val pop : 'a t -> 'a
       end = struct
+        module Queue = Stdlib.Queue
+
         type 'a t = {
           mutex : Mutex.t;
           queue : 'a Queue.t;