Optimize Mutex & AtomicCell

benchmarks/src/main/scala/cats/effect/benchmarks/AtomicCellBenchmark.scala

@@ -0,0 +1,111 @@
+/*
+ * Copyright 2020-2022 Typelevel
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cats.effect.benchmarks
+
+import cats.effect.IO
+import cats.effect.std._
+import cats.effect.unsafe.implicits.global
+import cats.syntax.all._
+
+import org.openjdk.jmh.annotations._
+
+import java.util.concurrent.TimeUnit
+
+/**
+ * To do comparative benchmarks between versions:
+ *
+ * benchmarks/run-benchmark AtomicCellBenchmark
+ *
+ * This will generate results in `benchmarks/results`.
+ *
+ * Or to run the benchmark from within sbt:
+ *
+ * Jmh / run -i 10 -wi 10 -f 2 -t 1 cats.effect.benchmarks.AtomicCellBenchmark
+ *
+ * Which means "10 iterations", "10 warm-up iterations", "2 forks", "1 thread". Please note that
+ * benchmarks should be usually executed at least in 10 iterations (as a rule of thumb), but
+ * more is better.
+ */
+@State(Scope.Thread)
+@BenchmarkMode(Array(Mode.Throughput))
+@OutputTimeUnit(TimeUnit.SECONDS)
+class AtomicCellBenchmark {
+  @Param(Array("10", "50", "100"))
+  var fibers: Int = _
+
+  @Param(Array("1000"))
+  var iterations: Int = _
+
+  private def happyPathImpl(cell: IO[AtomicCell[IO, Int]]): Unit = {
+    cell
+      .flatMap { c => c.evalUpdate(i => IO(i + 1)).replicateA_(fibers) }
+      .replicateA_(iterations)
+      .unsafeRunSync()
+  }
+
+  @Benchmark
+  def happyPathConcurrent(): Unit = {
+    happyPathImpl(cell = AtomicCell.concurrent(0))
+  }
+
+  @Benchmark
+  def happyPathAsync(): Unit = {
+    happyPathImpl(cell = AtomicCell.async(0))
+  }
+
+  private def highContentionImpl(cell: IO[AtomicCell[IO, Int]]): Unit = {
+    cell
+      .flatMap { c => c.evalUpdate(i => IO(i + 1)).parReplicateA_(fibers) }
+      .replicateA_(iterations)
+      .unsafeRunSync()
+  }
+
+  @Benchmark
+  def highContentionConcurrent(): Unit = {
+    highContentionImpl(cell = AtomicCell.concurrent(0))
+  }
+
+  @Benchmark
+  def highContentionAsync(): Unit = {
+    highContentionImpl(cell = AtomicCell.async(0))
+  }
+
+  private def cancellationImpl(cell: IO[AtomicCell[IO, Int]]): Unit = {
+    cell
+      .flatMap { c =>
+        c.evalUpdate { _ =>
+          c.evalUpdate(i => IO(i + 1))
+            .start
+            .flatMap(fiber => IO.cede >> fiber.cancel)
+            .parReplicateA_(fibers)
+            .as(-1)
+        }
+      }
+      .replicateA_(iterations)
+      .unsafeRunSync()
+  }
+
+  @Benchmark
+  def cancellationConcurrent(): Unit = {
+    cancellationImpl(cell = AtomicCell.concurrent(0))
+  }
+
+  @Benchmark
+  def cancellationAsync(): Unit = {
+    cancellationImpl(cell = AtomicCell.async(0))
+  }
+}

benchmarks/src/main/scala/cats/effect/benchmarks/MutexBenchmark.scala

@@ -0,0 +1,107 @@
+/*
+ * Copyright 2020-2022 Typelevel
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package cats.effect.benchmarks
+
+import cats.effect.IO
+import cats.effect.std._
+import cats.effect.unsafe.implicits.global
+import cats.syntax.all._
+
+import org.openjdk.jmh.annotations._
+
+import java.util.concurrent.TimeUnit
+
+/**
+ * To do comparative benchmarks between versions:
+ *
+ * benchmarks/run-benchmark MutexBenchmark
+ *
+ * This will generate results in `benchmarks/results`.
+ *
+ * Or to run the benchmark from within sbt:
+ *
+ * Jmh / run -i 10 -wi 10 -f 2 -t 1 cats.effect.benchmarks.MutexBenchmark
+ *
+ * Which means "10 iterations", "10 warm-up iterations", "2 forks", "1 thread". Please note that
+ * benchmarks should be usually executed at least in 10 iterations (as a rule of thumb), but
+ * more is better.
+ */
+@State(Scope.Thread)
+@BenchmarkMode(Array(Mode.Throughput))
+@OutputTimeUnit(TimeUnit.SECONDS)
+class MutexBenchmark {
+  @Param(Array("10", "50", "100"))
+  var fibers: Int = _
+
+  @Param(Array("1000"))
+  var iterations: Int = _
+
+  private def happyPathImpl(mutex: IO[Mutex[IO]]): Unit = {
+    mutex
+      .flatMap { m => m.lock.use_.replicateA_(fibers) }
+      .replicateA_(iterations)
+      .unsafeRunSync()
+  }
+
+  @Benchmark
+  def happyPathConcurrent(): Unit = {
+    happyPathImpl(mutex = Mutex.concurrent)
+  }
+
+  @Benchmark
+  def happyPathAsync(): Unit = {
+    happyPathImpl(mutex = Mutex.async)
+  }
+
+  private def highContentionImpl(mutex: IO[Mutex[IO]]): Unit = {
+    mutex
+      .flatMap { m => m.lock.use_.parReplicateA_(fibers) }
+      .replicateA_(iterations)
+      .unsafeRunSync()
+  }
+
+  @Benchmark
+  def highContentionConcurrent(): Unit = {
+    highContentionImpl(mutex = Mutex.concurrent)
+  }
+
+  @Benchmark
+  def highContentionAsync(): Unit = {
+    highContentionImpl(mutex = Mutex.async)
+  }
+
+  private def cancellationImpl(mutex: IO[Mutex[IO]]): Unit = {
+    mutex
+      .flatMap { m =>
+        m.lock.surround {
+          m.lock.use_.start.flatMap(fiber => IO.cede >> fiber.cancel).parReplicateA_(fibers)
+        }
+      }
+      .replicateA_(iterations)
+      .unsafeRunSync()
+  }
+
+  @Benchmark
+  def cancellationConcurrent(): Unit = {
+    cancellationImpl(mutex = Mutex.concurrent)
+  }
+
+  @Benchmark
+  def cancellationAsync(): Unit = {
+    cancellationImpl(mutex = Mutex.async)
+  }
+}

build.sbt

@@ -904,6 +904,10 @@ lazy val std = crossProject(JSPlatform, JVMPlatform, NativePlatform)
         "cats.effect.std.Queue#CircularBufferQueue.onOfferNoCapacity"),
       ProblemFilters.exclude[DirectMissingMethodProblem](
         "cats.effect.std.Queue#DroppingQueue.onOfferNoCapacity"),
+      // introduced by #3346
+      // private stuff
+      ProblemFilters.exclude[MissingClassProblem](
+        "cats.effect.std.Mutex$Impl"),
       // introduced by #3347
       // private stuff
       ProblemFilters.exclude[MissingClassProblem](

std/shared/src/main/scala/cats/effect/std/AtomicCell.scala

@@ -29,11 +29,11 @@ import cats.syntax.all._
  * calling fiber.
  *
  * {{{
- *   final class ParkingLot(data: AtomicCell[IO, ArraySeq[Boolean]], rnd: Random[IO]) {
+ *   final class ParkingLot(data: AtomicCell[IO, Vector[Boolean]], rnd: Random[IO]) {
  *     def getSpot: IO[Option[Int]] =
  *       data.evalModify { spots =>
  *         val availableSpots = spots.zipWithIndex.collect { case (true, idx) => idx }
- *         rnd.shuffleList(availableSpots).map { shuffled =>
+ *         rnd.shuffleVector(availableSpots).map { shuffled =>
  *           val acquired = shuffled.headOption
  *           val next = acquired.fold(spots)(a => spots.updated(a, false)) // mark the chosen spot as taken
  *           (next, shuffled.headOption)
@@ -131,7 +131,12 @@ object AtomicCell {
      * Initializes the `AtomicCell` using the provided value.
      */
     def of[A](init: A)(implicit F: Concurrent[F]): F[AtomicCell[F, A]] =
-      AtomicCell.concurrent(init)
+      F match {
+        case f: Async[F] =>
+          AtomicCell.async(init)(f)
+        case _ =>
+          AtomicCell.concurrent(init)
+      }
 
     @deprecated("Use the version that only requires Concurrent", since = "3.5.0")
     private[std] def of[A](init: A, F: Async[F]): F[AtomicCell[F, A]] =
@@ -148,9 +153,12 @@ object AtomicCell {
       of(M.empty)(F)
   }
 
+  private[effect] def async[F[_], A](init: A)(implicit F: Async[F]): F[AtomicCell[F, A]] =
+    Mutex.async[F].map(mutex => new AsyncImpl(init, mutex))
+
   private[effect] def concurrent[F[_], A](init: A)(
       implicit F: Concurrent[F]): F[AtomicCell[F, A]] =
-    (Ref.of[F, A](init), Mutex[F]).mapN { (ref, m) => new ConcurrentImpl(ref, m) }
+    (Ref.of[F, A](init), Mutex.concurrent[F]).mapN { (ref, m) => new ConcurrentImpl(ref, m) }
 
   private final class ConcurrentImpl[F[_], A](
       ref: Ref[F, A],
@@ -184,4 +192,50 @@ object AtomicCell {
     override def evalUpdateAndGet(f: A => F[A]): F[A] =
       evalModify(a => f(a).map(aa => (aa, aa)))
   }
+
+  private final class AsyncImpl[F[_], A](
+      init: A,
+      mutex: Mutex[F]
+  )(
+      implicit F: Async[F]
+  ) extends AtomicCell[F, A] {
+    private var cell: A = init
+
+    override def get: F[A] =
+      mutex.lock.surround {
+        F.delay {
+          cell
+        }
+      }
+
+    override def set(a: A): F[Unit] =
+      mutex.lock.surround {
+        F.delay {
+          cell = a
+        }
+      }
+
+    override def modify[B](f: A => (A, B)): F[B] =
+      evalModify(a => F.pure(f(a)))
+
+    override def evalModify[B](f: A => F[(A, B)]): F[B] =
+      mutex.lock.surround {
+        F.delay(cell).flatMap(f).flatMap {
+          case (a, b) =>
+            F.delay {
+              cell = a
+              b
+            }
+        }
+      }
+
+    override def evalUpdate(f: A => F[A]): F[Unit] =
+      evalModify(a => f(a).map(aa => (aa, ())))
+
+    override def evalGetAndUpdate(f: A => F[A]): F[A] =
+      evalModify(a => f(a).map(aa => (aa, a)))
+
+    override def evalUpdateAndGet(f: A => F[A]): F[A] =
+      evalModify(a => f(a).map(aa => (aa, aa)))
+  }
 }