[Storage] [DataMovement] Removed unnecessary synchronization primitives (Azure#47020)

* initial commit

* changes wording of comment

Author: nickliu-msft

sdk/storage/Azure.Storage.DataMovement/src/CommitChunkHandler.cs

@@ -92,11 +92,12 @@ public CommitChunkHandler(
                     SingleReader = true,
                 });
             _cancellationToken = cancellationToken;
-            _processStageChunkEvents = Task.Run(() => NotifyOfPendingStageChunkEvents());
 
             // Set bytes transferred to block size because we transferred the initial block
             _bytesTransferred = blockSize;
 
+            _processStageChunkEvents = Task.Run(() => NotifyOfPendingStageChunkEvents());
+
             _blockSize = blockSize;
             _transferOrder = transferOrder;
             if (_transferOrder == DataTransferOrder.Sequential)
@@ -155,7 +156,10 @@ private async Task NotifyOfPendingStageChunkEvents()
                     // Read one event argument at a time.
                     StageChunkEventArgs args = await _stageChunkChannel.Reader.ReadAsync(_cancellationToken).ConfigureAwait(false);
 
-                    Interlocked.Add(ref _bytesTransferred, args.BytesTransferred);
+                    // don't need to use Interlocked.Add() as we are reading one event at a time
+                    // and _bytesTransferred is not being read/updated from any other thread
+                    _bytesTransferred += args.BytesTransferred;
+
                     // Report the incremental bytes transferred
                     _reportProgressInBytes(args.BytesTransferred);
 

sdk/storage/Azure.Storage.DataMovement/src/DownloadChunkHandler.cs

@@ -107,6 +107,11 @@ public DownloadChunkHandler(
             ClientDiagnostics clientDiagnostics,
             CancellationToken cancellationToken)
         {
+            // Set bytes transferred to the length of bytes we got back from the initial
+            // download request
+            _bytesTransferred = currentTransferred;
+            _currentRangeIndex = 0;
+
             // Create channel of finished Stage Chunk Args to update the bytesTransferred
             // and for ending tasks like commit block.
             // The size of the channel should never exceed 50k (limit on blocks in a block blob).
@@ -143,10 +148,6 @@ public DownloadChunkHandler(
             _queueCompleteFileDownload = behaviors.QueueCompleteFileDownload
                 ?? throw Errors.ArgumentNull(nameof(behaviors.QueueCompleteFileDownload));
 
-            // Set bytes transferred to the length of bytes we got back from the initial
-            // download request
-            _bytesTransferred = currentTransferred;
-            _currentRangeIndex = 0;
             _rangesCount = ranges.Count;
             // Set size of the list of null streams
             _rangesCompleted = new ConcurrentDictionary<long, string>();
@@ -338,8 +339,9 @@ private async Task InvokeFailedEvent(Exception ex)
         /// <param name="bytesDownloaded"></param>
         private void UpdateBytesAndRange(long bytesDownloaded)
         {
-            Interlocked.Add(ref _bytesTransferred, bytesDownloaded);
-            Interlocked.Increment(ref _currentRangeIndex);
+            // don't need to use Interlocked since this is the only thread reading and updating these values
+            _bytesTransferred += bytesDownloaded;
+            _currentRangeIndex++;
             _reportProgressInBytes(bytesDownloaded);
         }
     }