Integrated timers

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

@@ -0,0 +1,78 @@
+/*
+ * 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.unsafe._
+import cats.syntax.all._
+
+import org.openjdk.jmh.annotations._
+
+import scala.concurrent.duration._
+
+import java.util.concurrent.TimeUnit
+
+/**
+ * To do comparative benchmarks between versions:
+ *
+ * benchmarks/run-benchmark SleepBenchmark
+ *
+ * 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.SleepBenchmark
+ *
+ * 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.MINUTES)
+class SleepBenchmark {
+
+  @Param(Array("10000"))
+  var size: Int = _
+
+  def sleepBenchmark(implicit runtime: IORuntime): Int = {
+    def fiber(i: Int): IO[Int] =
+      IO.sleep(1.nanosecond).flatMap { _ =>
+        IO(i).flatMap { j =>
+          IO.sleep(1.nanosecond).flatMap { _ =>
+            if (j > 1000)
+              IO.sleep(1.nanosecond).flatMap(_ => IO.pure(j))
+            else
+              IO.sleep(1.nanosecond).flatMap(_ => fiber(j + 1))
+          }
+        }
+      }
+
+    List
+      .range(0, size)
+      .traverse(fiber(_).start)
+      .flatMap(_.traverse(_.joinWithNever))
+      .map(_.sum)
+      .unsafeRunSync()
+  }
+
+  @Benchmark
+  def sleep(): Int = {
+    import cats.effect.unsafe.implicits.global
+    sleepBenchmark
+  }
+}

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

@@ -23,6 +23,9 @@ import scala.concurrent.duration._
 
 object SleepDrift extends IOApp.Simple {
 
+  override val runtimeConfig =
+    super.runtimeConfig.copy(cpuStarvationCheckInitialDelay = Duration.Inf)
+
   val delayTwoMinutes = {
     def loop(n: Int): IO[Unit] = {
       if (n <= 0)

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

@@ -165,36 +165,23 @@ class WorkStealingBenchmark {
       (ExecutionContext.fromExecutor(executor), () => executor.shutdown())
     }
 
-    val (scheduler, schedDown) = {
-      val executor = Executors.newSingleThreadScheduledExecutor { r =>
-        val t = new Thread(r)
-        t.setName("io-scheduler")
-        t.setDaemon(true)
-        t.setPriority(Thread.MAX_PRIORITY)
-        t
-      }
-      (Scheduler.fromScheduledExecutor(executor), () => executor.shutdown())
-    }
-
-    val compute =
-      new WorkStealingThreadPool(
-        256,
-        "io-compute",
-        "io-blocker",
-        60.seconds,
-        _.printStackTrace())
+    val compute = new WorkStealingThreadPool(
+      256,
+      "io-compute",
+      "io-blocker",
+      60.seconds,
+      _.printStackTrace())
 
     val cancelationCheckThreshold =
       System.getProperty("cats.effect.cancelation.check.threshold", "512").toInt
 
     IORuntime(
       compute,
       blocking,
-      scheduler,
+      compute,
       () => {
         compute.shutdown()
         blockDown()
-        schedDown()
       },
       IORuntimeConfig(
         cancelationCheckThreshold,

core/js-native/src/main/scala/cats/effect/unsafe/WorkStealingThreadPool.scala

@@ -18,6 +18,7 @@ package cats.effect
 package unsafe
 
 import scala.concurrent.ExecutionContext
+import scala.concurrent.duration.FiniteDuration
 
 // Can you imagine a thread pool on JS? Have fun trying to extend or instantiate
 // this class. Unfortunately, due to the explicit branching, this type leaks
@@ -27,6 +28,13 @@ private[effect] sealed abstract class WorkStealingThreadPool private ()
   def execute(runnable: Runnable): Unit
   def reportFailure(cause: Throwable): Unit
   private[effect] def reschedule(runnable: Runnable): Unit
+  private[effect] def sleepInternal(
+      delay: FiniteDuration,
+      callback: Right[Nothing, Unit] => Unit): Runnable
+  private[effect] def sleep(
+      delay: FiniteDuration,
+      task: Runnable,
+      fallback: Scheduler): Runnable
   private[effect] def canExecuteBlockingCode(): Boolean
   private[unsafe] def liveTraces(): (
       Map[Runnable, Trace],

core/jvm/src/main/scala/cats/effect/IOApp.scala

@@ -322,17 +322,13 @@ trait IOApp {
         val (blocking, blockDown) =
           IORuntime.createDefaultBlockingExecutionContext()
 
-        val (scheduler, schedDown) =
-          IORuntime.createDefaultScheduler()
-
         IORuntime(
           compute,
           blocking,
-          scheduler,
+          compute,
           { () =>
             compDown()
             blockDown()
-            schedDown()
           },
           runtimeConfig)
       }

core/jvm/src/main/scala/cats/effect/unsafe/IORuntimeCompanionPlatform.scala

@@ -180,8 +180,8 @@ private[unsafe] abstract class IORuntimeCompanionPlatform { this: IORuntime.type
       installGlobal {
         val (compute, _) = createWorkStealingComputeThreadPool()
         val (blocking, _) = createDefaultBlockingExecutionContext()
-        val (scheduler, _) = createDefaultScheduler()
-        IORuntime(compute, blocking, scheduler, () => (), IORuntimeConfig())
+
+        IORuntime(compute, blocking, compute, () => (), IORuntimeConfig())
       }
     }
 

core/jvm/src/main/scala/cats/effect/unsafe/SleepCallback.scala

@@ -0,0 +1,79 @@
+/*
+ * 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.unsafe
+
+import scala.concurrent.duration.FiniteDuration
+
+import java.util.concurrent.atomic.AtomicBoolean
+
+private final class SleepCallback private (
+    val triggerTime: Long,
+    private[this] var _callback: Right[Nothing, Unit] => Unit)
+    extends AtomicBoolean(true)
+    with Runnable {
+
+  def callback(r: Right[Nothing, Unit]): Unit = {
+    val cb = _callback
+    if (cb != null) {
+      cb(r)
+    }
+  }
+
+  override def run(): Unit = {
+    lazySet(false)
+    _callback = null // avoid memory leaks
+  }
+}
+
+private object SleepCallback {
+
+  /**
+   * Translated to Scala from:
+   * https://github.com/openjdk/jdk/blob/04a806ec86a388b8de31d42f904c4321beb69e14/src/java.base/share/classes/java/util/concurrent/ScheduledThreadPoolExecutor.java#L527-L547
+   */
+  def create(
+      delay: FiniteDuration,
+      callback: Right[Nothing, Unit] => Unit,
+      now: Long,
+      sleepers: SleepersQueue): SleepCallback = {
+
+    def overflowFree(delay: Long, now: Long): Long =
+      if (sleepers.isEmpty) delay
+      else {
+        val head = sleepers.head()
+        val headDelay = head.triggerTime - now
+        if (headDelay < 0 && (delay - headDelay < 0))
+          Long.MaxValue + headDelay
+        else
+          delay
+      }
+
+    val triggerTime = {
+      val delayNanos = delay.toNanos
+
+      if (delayNanos < (Long.MaxValue >> 1))
+        now + delayNanos
+      else
+        now + overflowFree(delayNanos, now)
+    }
+
+    new SleepCallback(triggerTime, callback)
+  }
+
+  implicit val sleepCallbackReverseOrdering: Ordering[SleepCallback] =
+    Ordering.fromLessThan(_.triggerTime > _.triggerTime)
+}

core/jvm/src/main/scala/cats/effect/unsafe/SleepersQueue.scala

@@ -0,0 +1,50 @@
+/*
+ * 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.unsafe
+
+import scala.collection.mutable.PriorityQueue
+
+private final class SleepersQueue private () {
+  private[this] val queue: PriorityQueue[SleepCallback] = PriorityQueue.empty
+  private[this] var count: Int = 0
+
+  def isEmpty: Boolean =
+    count == 0
+
+  def nonEmpty: Boolean =
+    !isEmpty
+
+  def head(): SleepCallback =
+    queue.head
+
+  def +=(scb: SleepCallback): Unit = {
+    queue += scb
+    count += 1
+  }
+
+  def popHead(): Unit = {
+    queue.dequeue()
+    count -= 1
+    ()
+  }
+
+  override def toString = s"SleepersQueue($queue, $count)"
+}
+
+private object SleepersQueue {
+  def empty: SleepersQueue = new SleepersQueue()
+}