From 5d0d88fdf6cdebeed7e1d47110e300893046b1dc Mon Sep 17 00:00:00 2001
From: Flavio Brasil <fwbrasil@gmail.com>
Date: Mon, 26 Feb 2024 23:34:13 -0800
Subject: [PATCH] scheduler improvements

---
 .../src/main/scala/kyo/scheduler/Flag.scala   |  9 +++--
 .../main/scala/kyo/scheduler/Scheduler.scala  | 39 ++++++++++++++++++-
 2 files changed, 43 insertions(+), 5 deletions(-)

diff --git a/kyo-core/jvm/src/main/scala/kyo/scheduler/Flag.scala b/kyo-core/jvm/src/main/scala/kyo/scheduler/Flag.scala
index 5f1a31629..034c17a80 100644
--- a/kyo-core/jvm/src/main/scala/kyo/scheduler/Flag.scala
+++ b/kyo-core/jvm/src/main/scala/kyo/scheduler/Flag.scala
@@ -4,10 +4,11 @@ private object Flag:
     abstract class Reader[T]:
         def apply(s: String): T
     object Reader:
-        given Reader[Int]    = Integer.parseInt(_)
-        given Reader[String] = identity(_)
-        given Reader[Long]   = java.lang.Long.parseLong(_)
-        given Reader[Double] = java.lang.Double.parseDouble(_)
+        given Reader[Int]     = Integer.parseInt(_)
+        given Reader[String]  = identity(_)
+        given Reader[Long]    = java.lang.Long.parseLong(_)
+        given Reader[Double]  = java.lang.Double.parseDouble(_)
+        given Reader[Boolean] = java.lang.Boolean.parseBoolean(_)
         given listReader[T](using r: Reader[T]): Reader[List[T]] =
             (s: String) => s.split(",").toList.map(r(_))
     end Reader
diff --git a/kyo-core/jvm/src/main/scala/kyo/scheduler/Scheduler.scala b/kyo-core/jvm/src/main/scala/kyo/scheduler/Scheduler.scala
index 50e2b76b2..cb34abe36 100644
--- a/kyo-core/jvm/src/main/scala/kyo/scheduler/Scheduler.scala
+++ b/kyo-core/jvm/src/main/scala/kyo/scheduler/Scheduler.scala
@@ -1,6 +1,7 @@
 package kyo.scheduler
 
 import java.util.concurrent.Executors
+import java.util.concurrent.TimeUnit
 import java.util.concurrent.atomic.AtomicInteger
 import kyo.*
 import org.jctools.queues.MpmcUnboundedXaddArrayQueue
@@ -8,9 +9,11 @@ import scala.annotation.tailrec
 
 private[kyo] object Scheduler:
 
+    private val printStatus = Flag("printStatus", false)
+
     private val coreWorkers = Flag(
         "coreWorkers",
-        Math.ceil(Runtime.getRuntime().availableProcessors().toDouble / 2).intValue()
+        Math.min(1, Math.ceil(Runtime.getRuntime().availableProcessors().toDouble / 2).intValue())
     )
 
     @volatile
@@ -21,8 +24,18 @@ private[kyo] object Scheduler:
     private val pool = Executors.newCachedThreadPool(Threads("kyo-worker", new Worker(_)))
 
     startWorkers()
+
     Coordinator.load()
 
+    if printStatus then
+        discard(Executors.newSingleThreadScheduledExecutor().scheduleAtFixedRate(
+            (() => println(status())): Runnable,
+            1,
+            1,
+            TimeUnit.SECONDS
+        ))
+    end if
+
     def removeWorker(): Unit =
         if concurrencyLimit > coreWorkers then
             concurrencyLimit = Math.max(1, concurrency.get() - 1)
@@ -67,6 +80,8 @@ private[kyo] object Scheduler:
     end schedule
 
     def steal(thief: Worker): IOTask[?] =
+        if Worker.all.size() <= 1 then
+            return null
         // p2c load stealing
         var r: IOTask[?] = null
         var w0: Worker   = randomWorker(thief)
@@ -116,6 +131,28 @@ private[kyo] object Scheduler:
         w
     end randomWorker
 
+    def status(): String =
+        val sb = new StringBuilder
+
+        sb.append("===== Kyo Scheduler =====\n")
+        sb.append(f"${"Load"}%-8s ${"Workers"}%-8s ${"Limit"}%-8s\n")
+        sb.append(f"${loadAvg()}%-8.2f ${concurrency.get()}%-8d ${concurrencyLimit}%-8d\n")
+        sb.append("\n")
+
+        sb.append(
+            f"${"Thread"}%-20s ${"Load"}%-5s ${"State"}%-15s ${"Frame"}%-30s\n"
+        )
+
+        Worker.all.iterator().forEachRemaining { worker =>
+            sb.append(
+                f"${worker.getName}%-20s ${worker.load()}%-5.2f ${worker.getState}%-15s ${worker.getStackTrace()(0)}%-30s\n"
+            )
+        }
+        sb.append("=========================\n")
+
+        sb.toString()
+    end status
+
     override def toString =
         s"Scheduler(loadAvg=${loadAvg()},concurrency=$concurrency,limit=$concurrencyLimit)"
 end Scheduler