Change to use Picos instead of DLA and DLT

This adds support for cancelation through Picos and removes explicit support for
timeouts, which simplifies the library.

Support for DLA and DLT is removed.

This basically also means that one can no longer use Kcas without a scheduler.

Author: polytypic

CHANGES.md

@@ -1,3 +1,9 @@
+## Next version
+
+- Changed to use [Picos](https://github.com/ocaml-multicore/picos/) instead of
+  [DLA](https://github.com/ocaml-multicore/domain-local-await/) and
+  [DLT](https://github.com/ocaml-multicore/domain-local-timeout/) (@polytypic)
+
 ## 0.7.0
 
 - Numerous minor internal improvements (@polytypic)

README.md

@@ -47,8 +47,8 @@ Features and properties:
   read-only compare (CMP) operations that can be performed on overlapping
   locations in parallel without interference.
 
-- **_Blocking await_**: The algorithm supports timeouts and awaiting for changes
-  to any number of shared memory locations.
+- **_Blocking await_**: The algorithm supports cancelation and awaiting for
+  changes to any number of shared memory locations.
 
 - **_Composable_**: Independently developed transactions can be composed with
   ease sequentially, conjunctively, conditionally, and disjunctively.
@@ -76,7 +76,7 @@ is distributed under the [ISC license](LICENSE.md).
     - [A transactional lock-free queue](#a-transactional-lock-free-queue)
     - [Composing transactions](#composing-transactions)
     - [Blocking transactions](#blocking-transactions)
-    - [Timeouts](#timeouts)
+    - [Cancelation and Timeouts](#cancelation-and-timeouts)
     - [A transactional lock-free leftist heap](#a-transactional-lock-free-leftist-heap)
   - [Programming with transactional data structures](#programming-with-transactional-data-structures)
     - [The dining philosophers problem](#the-dining-philosophers-problem)
@@ -101,14 +101,7 @@ is distributed under the [ISC license](LICENSE.md).
 
 To use the library
 
-<!--
 ```ocaml
-# #thread
-```
--->
-
-```ocaml
-# #require "kcas"
 # open Kcas
 ```
 
@@ -143,6 +136,7 @@ Block waiting for changes to locations:
 
 ```ocaml
 # let a_domain = Domain.spawn @@ fun () ->
+    Scheduler.run @@ fun () ->
     let x = Loc.get_as (fun x -> Retry.unless (x <> 0); x) x in
     Printf.sprintf "The answer is %d!" x
 val a_domain : string Domain.t = <abstr>
@@ -551,13 +545,28 @@ and then spawn a domain that tries to atomically both pop and dequeue:
 
 ```ocaml
 # let a_domain = Domain.spawn @@ fun () ->
+    Scheduler.run @@ fun () ->
     let tx ~xt = (pop ~xt a_stack, dequeue ~xt a_queue) in
     let (popped, dequeued) = Xt.commit { tx } in
     Printf.sprintf "I popped %d and dequeued %d!"
       popped dequeued
 val a_domain : string Domain.t = <abstr>
 ```
 
+**Kcas** uses the [Picos](https://github.com/ocaml-multicore/picos/) interface
+to implement blocking. Above `Scheduler.run` starts an effects based
+[Picos compatible](https://ocaml-multicore.github.io/picos/doc/picos/index.html#interoperability)
+scheduler, which allows **Kcas** to block in a scheduler friendly manner.
+
+> **_Note_**: Typically your entire program would run inside a scheduler and you
+> should
+> [fork fibers](https://ocaml-multicore.github.io/picos/doc/picos_mux/index.html#examples)
+> rather than spawn domains and start schedulers. The
+> [MDX](https://github.com/realworldocaml/mdx) tool used for checking this
+> document does not allow one to start a scheduler once and run individual code
+> snippets within the scheduler, which is why individual examples spawn domains
+> and start schedulers.
+
 The domain is now blocked waiting for changes to the stack and the queue. As
 long as we don't populate both at the same time
 
@@ -585,7 +594,7 @@ The retry mechanism essentially allows a transaction to wait for an arbitrary
 condition and can function as a fairly expressive communication and
 synchronization mechanism.
 
-#### Timeouts
+#### Cancelation and Timeouts
 
 > If you block, will they come?
 
@@ -605,43 +614,30 @@ val pop_or_raise_if :
   xt:'a Xt.t -> bool Loc.t -> 'b list Loc.t -> xt:'c Xt.t -> 'b = <fun>
 ```
 
-This works, but creating, checking, and canceling timeouts properly can be a lot
-of work. Therefore **Kcas** also directly supports an optional `timeoutf`
-argument for potentially blocking operations. For example, to perform a blocking
-pop with a timeout, one can simply explicitly pass the desired timeout in
-seconds:
-
-```ocaml
-# let an_empty_stack = stack () in
-  Xt.commit ~timeoutf:0.1 { tx = pop an_empty_stack }
-Exception: Failure "Domain_local_timeout.set_timeoutf not implemented".
-```
-
-Oops! What happened above is that the
-[_domain local timeout_](https://github.com/ocaml-multicore/domain-local-timeout)
-mechanism used by **Kcas** was not implemented on the current domain. The idea
-is that, in the future, concurrent schedulers provide the mechanism out of the
-box, but there is also a default implementation using the Stdlib `Thread` and
-`Unix` modules that works on most platforms. However, to avoid direct
-dependencies to `Thread` and `Unix`, we need to explicitly tell the library that
-it can use those modules:
+This works, but creating, checking, and canceling timeouts properly in this
+manner can be a lot of work. Therefore **Kcas** also directly supports
+[cancelation](https://ocaml-multicore.github.io/picos/doc/picos_std/Picos_std_structured/index.html#understanding-cancelation)
+through the [Picos](https://github.com/ocaml-multicore/picos/) interface. This
+both allows **Kcas** transactions to be cleanly terminated in case the program
+has encountered an error and also allows one to simply use a timeout mechanism
+provided by the scheduler. For example, the sample
+[structured concurrency library](https://ocaml-multicore.github.io/picos/doc/picos_std/Picos_std_structured/index.html)
 
 ```ocaml
-# Domain_local_timeout.set_system (module Thread) (module Unix)
-- : unit = ()
+# open Picos_std_structured
 ```
 
-This initialization, if needed, should be done by application code rather than
-by libraries.
-
-If we now retry the previous example we will get a
-[`Timeout`](https://ocaml-multicore.github.io/kcas/doc/kcas/Kcas/Timeout/index.html#exception-Timeout)
-exception as expected:
+for Picos provides the
+[`Control.terminate_after`](https://ocaml-multicore.github.io/picos/doc/picos_std/Picos_std_structured/Control/index.html#val-terminate_after)
+operation, which allows one to easily run an operation with a timeout on the
+current fiber:
 
 ```ocaml
 # let an_empty_stack = stack () in
-  Xt.commit ~timeoutf:0.1 { tx = pop an_empty_stack }
-Exception: Kcas.Timeout.Timeout.
+  Scheduler.run @@ fun () ->
+  Control.terminate_after ~seconds:0.1 @@ fun () ->
+  Xt.commit { tx = pop an_empty_stack }
+Exception: Picos_std_structured__Control.Terminate.
 ```
 
 Besides
@@ -651,7 +647,7 @@ potentially blocking single location operations such as
 [`update`](https://ocaml-multicore.github.io/kcas/doc/kcas/Kcas/Loc/index.html#val-update),
 and
 [`modify`](https://ocaml-multicore.github.io/kcas/doc/kcas/Kcas/Loc/index.html#val-modify)
-support the optional `timeoutf` argument.
+support cancelation.
 
 #### A transactional lock-free leftist heap
 
@@ -839,10 +835,9 @@ structures.
 One source of ready-made data structures is
 [**Kcas_data**](https://ocaml-multicore.github.io/kcas/doc/kcas_data/Kcas_data/index.html).
 Let's explore how we can leverage those data structures. Of course, first we
-need to `#require` the package and we'll also open it for convenience:
+open `Kcas_data` for convenience:
 
 ```ocaml
-# #require "kcas_data"
 # open Kcas_data
 ```
 
@@ -915,6 +910,7 @@ the philosophers:
     in
     Array.iter Domain.join @@ Array.init philosophers @@ fun i ->
       Domain.spawn @@ fun () ->
+      Scheduler.run @@ fun () ->
       let fork_lhs = forks.(i)
       and fork_rhs = forks.((i + 1) mod philosophers)
       and eaten = eaten.(i) in

bench/bench_accumulator.ml

@@ -9,6 +9,7 @@ let run_one ~budgetf ~n_domains ?(n_ops = 180 * Util.iter_factor) () =
   let n_ops_todo = Countdown.create ~n_domains () in
 
   let init _ = Countdown.non_atomic_set n_ops_todo n_ops in
+  let wrap _ _ action = Scheduler.run action in
   let work domain_index () =
     let rec work () =
       let n = Countdown.alloc n_ops_todo ~domain_index ~batch:1000 in
@@ -31,7 +32,7 @@ let run_one ~budgetf ~n_domains ?(n_ops = 180 * Util.iter_factor) () =
       (if n_domains = 1 then "" else "s")
   in
 
-  Times.record ~budgetf ~n_domains ~init ~work ()
+  Times.record ~budgetf ~n_domains ~init ~wrap ~work ()
   |> Times.to_thruput_metrics ~n:n_ops ~config ~singular:"operation"
 
 let run_suite ~budgetf =

bench/bench_dllist.ml

@@ -12,9 +12,10 @@ let run_single ~budgetf ?(n_msgs = 15 * Util.iter_factor) () =
     assert (Dllist.is_empty t);
     Util.generate_push_and_pop_sequence n_msgs
   in
+  let wrap _ _ action = Scheduler.run action in
   let work _ bits = Util.Bits.iter op bits in
 
-  Times.record ~budgetf ~n_domains:1 ~init ~work ()
+  Times.record ~budgetf ~n_domains:1 ~init ~wrap ~work ()
   |> Times.to_thruput_metrics ~n:n_msgs ~singular:"message" ~config:"one domain"
 
 let run_one ~budgetf ?(n_adders = 2) ?(n_takers = 2) ?(factor = 1)
@@ -31,6 +32,7 @@ let run_one ~budgetf ?(n_adders = 2) ?(n_takers = 2) ?(factor = 1)
     Countdown.non_atomic_set n_msgs_to_take n_msgs;
     Countdown.non_atomic_set n_msgs_to_add n_msgs
   in
+  let wrap _ _ action = Scheduler.run action in
   let work i () =
     if i < n_adders then
       let domain_index = i in
@@ -72,7 +74,7 @@ let run_one ~budgetf ?(n_adders = 2) ?(n_takers = 2) ?(factor = 1)
       (format "taker" false n_takers)
   in
 
-  Times.record ~budgetf ~n_domains ~init ~work ()
+  Times.record ~budgetf ~n_domains ~init ~wrap ~work ()
   |> Times.to_thruput_metrics ~n:n_msgs ~singular:"message" ~config
 
 let run_suite ~budgetf =

bench/bench_hashtbl.ml

@@ -24,7 +24,7 @@ let run_one ~budgetf ~n_domains ?(n_ops = 40 * Util.iter_factor)
     Countdown.non_atomic_set n_ops_todo n_ops;
     Random.State.make_self_init ()
   in
-
+  let wrap _ _ action = Scheduler.run action in
   let work domain_index state =
     let rec work () =
       let n = Countdown.alloc n_ops_todo ~domain_index ~batch:1000 in
@@ -56,7 +56,7 @@ let run_one ~budgetf ~n_domains ?(n_ops = 40 * Util.iter_factor)
       percent_read
   in
 
-  Times.record ~budgetf ~n_domains ~init ~work ()
+  Times.record ~budgetf ~n_domains ~init ~wrap ~work ()
   |> Times.to_thruput_metrics ~n:n_ops ~singular:"operation" ~config
 
 let run_suite ~budgetf =

bench/bench_mvar.ml

@@ -14,6 +14,7 @@ let run_one ~budgetf ?(n_adders = 2) ?(blocking_add = false) ?(n_takers = 2)
     Countdown.non_atomic_set n_msgs_to_take n_msgs;
     Countdown.non_atomic_set n_msgs_to_add n_msgs
   in
+  let wrap _ _ action = Scheduler.run action in
   let work i () =
     if i < n_adders then
       let domain_index = i in
@@ -81,7 +82,7 @@ let run_one ~budgetf ?(n_adders = 2) ?(blocking_add = false) ?(n_takers = 2)
       (format "taker" blocking_take n_takers)
   in
 
-  Times.record ~budgetf ~n_domains ~init ~work ()
+  Times.record ~budgetf ~n_domains ~init ~wrap ~work ()
   |> Times.to_thruput_metrics ~n:n_msgs ~singular:"message" ~config
 
 let run_suite ~budgetf =

bench/bench_parallel_cmp.ml

@@ -14,6 +14,7 @@ let run_one ~budgetf ~n_domains ?(n_ops = 50 * Util.iter_factor) () =
     Countdown.non_atomic_set n_ops_todo n_ops;
     Array.unsafe_get xs i
   in
+  let wrap _ _ action = Scheduler.run action in
   let work domain_index x =
     let tx1 ~xt =
       let a = Xt.get ~xt a in
@@ -41,7 +42,7 @@ let run_one ~budgetf ~n_domains ?(n_ops = 50 * Util.iter_factor) () =
     Printf.sprintf "%d worker%s" n_domains (if n_domains = 1 then "" else "s")
   in
 
-  Times.record ~budgetf ~n_domains ~init ~work ()
+  Times.record ~budgetf ~n_domains ~init ~wrap ~work ()
   |> Times.to_thruput_metrics ~n:n_ops ~singular:"transaction" ~config
 
 let run_suite ~budgetf =

bench/bench_queue.ml

@@ -10,9 +10,10 @@ let run_one_domain ~budgetf ?(n_msgs = 50 * Util.iter_factor) () =
     assert (Queue.is_empty t);
     Util.generate_push_and_pop_sequence n_msgs
   in
+  let wrap _ _ action = Scheduler.run action in
   let work _ bits = Util.Bits.iter op bits in
 
-  Times.record ~budgetf ~n_domains:1 ~init ~work ()
+  Times.record ~budgetf ~n_domains:1 ~init ~wrap ~work ()
   |> Times.to_thruput_metrics ~n:n_msgs ~singular:"message" ~config:"one domain"
 
 let run_one ~budgetf ?(n_adders = 2) ?(blocking_add = false) ?(n_takers = 2)
@@ -29,6 +30,7 @@ let run_one ~budgetf ?(n_adders = 2) ?(blocking_add = false) ?(n_takers = 2)
     Countdown.non_atomic_set n_msgs_to_take n_msgs;
     Countdown.non_atomic_set n_msgs_to_add n_msgs
   in
+  let wrap _ _ action = Scheduler.run action in
   let work i () =
     if i < n_adders then
       let domain_index = i in
@@ -82,7 +84,7 @@ let run_one ~budgetf ?(n_adders = 2) ?(blocking_add = false) ?(n_takers = 2)
       (format "taker" blocking_take n_takers)
   in
 
-  Times.record ~budgetf ~n_domains ~init ~work ()
+  Times.record ~budgetf ~n_domains ~init ~wrap ~work ()
   |> Times.to_thruput_metrics ~n:n_msgs ~singular:"message" ~config
 
 let run_suite ~budgetf =

bench/bench_stack.ml

@@ -10,9 +10,10 @@ let run_one_domain ~budgetf ?(n_msgs = 50 * Util.iter_factor) () =
     assert (Stack.is_empty t);
     Util.generate_push_and_pop_sequence n_msgs
   in
+  let wrap _ _ action = Scheduler.run action in
   let work _ bits = Util.Bits.iter op bits in
 
-  Times.record ~budgetf ~n_domains:1 ~init ~work ()
+  Times.record ~budgetf ~n_domains:1 ~init ~wrap ~work ()
   |> Times.to_thruput_metrics ~n:n_msgs ~singular:"message" ~config:"one domain"
 
 let run_one ~budgetf ?(n_adders = 2) ?(blocking_add = false) ?(n_takers = 2)
@@ -29,6 +30,7 @@ let run_one ~budgetf ?(n_adders = 2) ?(blocking_add = false) ?(n_takers = 2)
     Countdown.non_atomic_set n_msgs_to_take n_msgs;
     Countdown.non_atomic_set n_msgs_to_add n_msgs
   in
+  let wrap _ _ action = Scheduler.run action in
   let work i () =
     if i < n_adders then
       let domain_index = i in
@@ -82,7 +84,7 @@ let run_one ~budgetf ?(n_adders = 2) ?(blocking_add = false) ?(n_takers = 2)
       (format "taker" blocking_take n_takers)
   in
 
-  Times.record ~budgetf ~n_domains ~init ~work ()
+  Times.record ~budgetf ~n_domains ~init ~wrap ~work ()
   |> Times.to_thruput_metrics ~n:n_msgs ~singular:"message" ~config
 
 let run_suite ~budgetf =

bench/bench_xt.ml

@@ -15,6 +15,7 @@ let run_one ~budgetf ?(n_locs = 2)
   in
 
   let init _ = () in
+  let wrap _ _ action = Scheduler.run action in
   let work _ () =
     let rec loop i =
       if i > 0 then begin
@@ -27,7 +28,7 @@ let run_one ~budgetf ?(n_locs = 2)
 
   let config = Printf.sprintf "%d loc tx" n_locs in
 
-  Times.record ~budgetf ~n_domains:1 ~init ~work ()
+  Times.record ~budgetf ~n_domains:1 ~init ~wrap ~work ()
   |> Times.to_thruput_metrics ~n:n_iter ~singular:"transaction" ~config
 
 let run_suite ~budgetf =

bench/bench_xt_ro.ml

@@ -15,6 +15,7 @@ let run_one ~budgetf ?(n_locs = 2)
   in
 
   let init _ = () in
+  let wrap _ _ action = Scheduler.run action in
   let work _ () =
     let rec loop i =
       if i > 0 then begin
@@ -27,7 +28,7 @@ let run_one ~budgetf ?(n_locs = 2)
 
   let config = Printf.sprintf "%d loc tx" n_locs in
 
-  Times.record ~budgetf ~n_domains:1 ~init ~work ()
+  Times.record ~budgetf ~n_domains:1 ~init ~wrap ~work ()
   |> Times.to_thruput_metrics ~n:n_iter ~singular:"transaction" ~config
 
 let run_suite ~budgetf =

bench/dune

@@ -19,4 +19,4 @@
    (run %{test} -brief "Kcas_data Mvar")
    (run %{test} -brief "Kcas_data Queue")
    (run %{test} -brief "Kcas_data Stack")))
- (libraries kcas_data multicore-bench backoff multicore-magic))
+ (libraries backoff kcas_data multicore-bench multicore-magic scheduler))

doc/dune

@@ -5,4 +5,4 @@
   (package kcas_data))
  (enabled_if
   (>= %{ocaml_version} 5.0.0))
- (files gkmz-with-read-only-cmp-ops.md scheduler-interop.md))
+ (files gkmz-with-read-only-cmp-ops.md))