spinning tweaks

Author: VSadov

src/libraries/System.Private.CoreLib/src/System/Threading/LowLevelLifoSemaphore.cs

@@ -111,13 +111,13 @@ public bool Wait(int timeoutMs, short activeThreadCount)
             return WaitSlow(timeoutMs, activeThreadCount);
         }
 
-        private bool WaitSlow(int timeoutMs, short activeThreadCount)
+        private bool WaitSlow(int timeoutMs, short tpThreadCount)
         {
             // Now spin briefly with exponential backoff.
             // We estimate availability of CPU resources and limit spin count accordingly.
             // See comments on DefaultSemaphoreSpinCountLimit for more details.
             // Count current thread as active for the duration of spinning.
-            int active = activeThreadCount + 1;
+            int active = tpThreadCount - _separated._counts.WaiterCount;
             int available = _procCount - active;
             int spinStep = _maxSpinCount * 2 / _procCount;
             // With activeThreadCount arbitrarily large and _procCount arbitrarily small

src/libraries/System.Private.CoreLib/src/System/Threading/PortableThreadPool.Blocking.cs

@@ -260,7 +260,7 @@ private enum PendingBlockingAdjustment : byte
         private static class BlockingConfig
         {
             public static readonly bool IsCooperativeBlockingEnabled =
-                AppContextConfigHelper.GetBooleanConfig("System.Threading.ThreadPool.Blocking.CooperativeBlocking", true);
+                AppContextConfigHelper.GetBooleanConfig("System.Threading.ThreadPool.Blocking.CooperativeBlocking", "DOTNET_ThreadPool_CooperativeBlocking", true);
             public static readonly bool IgnoreMemoryUsage =
                 AppContextConfigHelper.GetBooleanConfig("System.Threading.ThreadPool.Blocking.IgnoreMemoryUsage", false);
 

src/libraries/System.Private.CoreLib/src/System/Threading/PortableThreadPool.WorkerThread.cs

@@ -105,7 +105,7 @@ private static void WorkerThreadStart()
 
                 while (true)
                 {
-                    while (semaphore.Wait(timeoutMs, threadPoolInstance._separated.counts.NumProcessingWork))
+                    while (semaphore.Wait(timeoutMs, threadPoolInstance._separated.counts.NumExistingThreads))
                     {
                         WorkerDoWork(threadPoolInstance);
                     }

src/libraries/System.Private.CoreLib/src/System/Threading/ThreadPoolWorkQueue.cs

@@ -857,8 +857,11 @@ internal static bool Dispatch()
                 // Missing a steal means there may be an item that we were unable to get.
                 // Effectively, we failed to fulfill our promise to check the queues for work.
                 // We need to make sure someone will do another pass.
+                // We do not need to do that right away though as that might result in a bunch
+                // of threads inviting each other while mostly seeing missed steals.
                 if (missedSteal)
                 {
+                    Thread.Sleep(1);
                     ThreadPool.EnsureWorkerRequested();
                 }
 
@@ -918,6 +921,7 @@ internal static bool Dispatch()
                         //
                         if (missedSteal)
                         {
+                            Thread.Sleep(1);
                             ThreadPool.EnsureWorkerRequested();
                         }