Insert Thread.Yield() in some spinloops (#392)

Author: TedHartMS

cs/src/core/Allocator/AllocatorBase.cs

@@ -845,7 +845,7 @@ public void ShiftBeginAddress(long newBeginAddress)
             epoch.Suspend();
 
             // Wait for flush to complete
-            while (FlushedUntilAddress < newBeginAddress) ;
+            while (FlushedUntilAddress < newBeginAddress) Thread.Yield();
 
             // Then shift head address
             var h = Utility.MonotonicUpdate(ref HeadAddress, newBeginAddress, out long old);

cs/src/core/Index/FASTER/LogAccessor.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Reflection;
+using System.Threading;
 
 namespace FASTER.core
 {
@@ -82,7 +83,7 @@ public void ShiftHeadAddress(long newHeadAddress, bool wait)
                 fht.epoch.Resume();
                 allocator.ShiftHeadAddress(newHeadAddress);
                 fht.epoch.Suspend();
-                while (wait && allocator.SafeHeadAddress < newHeadAddress) ;
+                while (wait && allocator.SafeHeadAddress < newHeadAddress) Thread.Yield();
             }
             else
             {
@@ -137,7 +138,7 @@ public void ShiftReadOnlyAddress(long newReadOnlyAddress, bool wait)
                 fht.epoch.Suspend();
 
                 // Wait for flush to complete
-                while (wait && allocator.FlushedUntilAddress < newReadOnlyAddress) ;
+                while (wait && allocator.FlushedUntilAddress < newReadOnlyAddress) Thread.Yield();
             }
             else
             {

cs/src/core/Index/FasterLog/FasterLog.cs

@@ -414,7 +414,7 @@ public void WaitForCommit(long untilAddress = 0)
             var tailAddress = untilAddress;
             if (tailAddress == 0) tailAddress = allocator.GetTailAddress();
 
-            while (CommittedUntilAddress < tailAddress) ;
+            while (CommittedUntilAddress < tailAddress) Thread.Yield();
         }
 
         /// <summary>
@@ -546,7 +546,7 @@ public long EnqueueAndWaitForCommit(byte[] entry)
         {
             long logicalAddress;
             while (!TryEnqueue(entry, out logicalAddress)) ;
-            while (CommittedUntilAddress < logicalAddress + 1) ;
+            while (CommittedUntilAddress < logicalAddress + 1) Thread.Yield();
             return logicalAddress;
         }
 
@@ -560,7 +560,7 @@ public long EnqueueAndWaitForCommit(ReadOnlySpan<byte> entry)
         {
             long logicalAddress;
             while (!TryEnqueue(entry, out logicalAddress)) ;
-            while (CommittedUntilAddress < logicalAddress + 1) ;
+            while (CommittedUntilAddress < logicalAddress + 1) Thread.Yield();
             return logicalAddress;
         }
 
@@ -574,7 +574,7 @@ public long EnqueueAndWaitForCommit(IReadOnlySpanBatch readOnlySpanBatch)
         {
             long logicalAddress;
             while (!TryEnqueue(readOnlySpanBatch, out logicalAddress)) ;
-            while (CommittedUntilAddress < logicalAddress + 1) ;
+            while (CommittedUntilAddress < logicalAddress + 1) Thread.Yield();
             return logicalAddress;
         }