diff --git a/org.eclipse.lsp4e/src/org/eclipse/lsp4e/LaunchConfigurationStreamProvider.java b/org.eclipse.lsp4e/src/org/eclipse/lsp4e/LaunchConfigurationStreamProvider.java
index e21014d2e..3a0725982 100644
--- a/org.eclipse.lsp4e/src/org/eclipse/lsp4e/LaunchConfigurationStreamProvider.java
+++ b/org.eclipse.lsp4e/src/org/eclipse/lsp4e/LaunchConfigurationStreamProvider.java
@@ -8,6 +8,7 @@
  *
  * Contributors:
  *   Mickael Istria (Red Hat Inc.) - initial implementation
+ *   Sebastian Thomschke - re-implement StreamProxyInputStream for better performance
  *******************************************************************************/
 package org.eclipse.lsp4e;
 
@@ -17,10 +18,8 @@
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.lang.reflect.Method;
-import java.nio.charset.Charset;
-import java.util.ArrayList;
 import java.util.Collections;
-import java.util.List;
+import java.util.Objects;
 import java.util.Set;
 import java.util.concurrent.ConcurrentLinkedQueue;
 
@@ -45,8 +44,8 @@
 import org.eclipse.lsp4e.server.StreamConnectionProvider;
 
 /**
- * Access and control IO streams from a Launch Configuration to connect
- * them to language server protocol client.
+ * Access and control IO streams from a Launch Configuration to connect them to
+ * language server protocol client.
  */
 public class LaunchConfigurationStreamProvider implements StreamConnectionProvider, IAdaptable {
 
@@ -60,43 +59,76 @@ public class LaunchConfigurationStreamProvider implements StreamConnectionProvid
 
 	protected static class StreamProxyInputStream extends InputStream implements IStreamListener {
 
-		private final ConcurrentLinkedQueue<Byte> queue = new ConcurrentLinkedQueue<>();
+		private static final int EOF = -1;
+		private static final byte[] NO_DATA = new byte[0];
+
+		private final ConcurrentLinkedQueue<byte[]> queue = new ConcurrentLinkedQueue<>();
 		private final IProcess process;
+		private byte[] currentBuffer = NO_DATA;
+		private int currentBufferPos = 0;
 
 		public StreamProxyInputStream(IProcess process) {
 			this.process = process;
 		}
 
 		@Override
-		public void streamAppended(String text, IStreamMonitor monitor) {
-			byte[] bytes = text.getBytes(Charset.defaultCharset());
-			List<Byte> bytesAsList = new ArrayList<>(bytes.length);
-			for (byte b : bytes) {
-				bytesAsList.add(b);
+		public void streamAppended(final String text, final IStreamMonitor monitor) {
+			final byte[] bytes = text.getBytes();
+			if (bytes.length > 0) {
+				queue.offer(bytes);
 			}
-			queue.addAll(bytesAsList);
 		}
 
 		@Override
 		public int read() throws IOException {
-			while (queue.isEmpty()) {
-				if (this.process.isTerminated()) {
-					return -1;
-				}
-				try {
-					Thread.sleep(5, 0);
-				} catch (InterruptedException e) {
-					Thread.currentThread().interrupt();
+			if (currentBufferPos >= currentBuffer.length && !fillCurrentBuffer()) {
+				return EOF;
+			}
+			return currentBuffer[currentBufferPos++] & 0xFF;
+		}
+
+		@Override
+		public int read(final byte[] buf, final int off, final int len) throws IOException {
+			Objects.checkFromIndexSize(off, len, buf.length);
+			if (len == 0) {
+				return 0;
+			}
+
+			int totalBytesRead = 0;
+			while (totalBytesRead < len) {
+				if (currentBufferPos >= currentBuffer.length && !fillCurrentBuffer()) {
+					return totalBytesRead == 0 ? EOF : totalBytesRead;
 				}
+
+				final int bytesToRead = Math.min(len - totalBytesRead, currentBuffer.length - currentBufferPos);
+				System.arraycopy(currentBuffer, currentBufferPos, buf, off + totalBytesRead, bytesToRead);
+				currentBufferPos += bytesToRead;
+				totalBytesRead += bytesToRead;
 			}
-			return castNonNull(queue.poll());
+			return totalBytesRead;
 		}
 
 		@Override
 		public int available() throws IOException {
-			return queue.size();
+			return (currentBuffer.length - currentBufferPos) + queue.stream().mapToInt(arr -> arr.length).sum();
 		}
 
+		private boolean fillCurrentBuffer() throws IOException {
+			try {
+				while (queue.isEmpty()) {
+					if (process.isTerminated()) {
+						return false;
+					}
+					Thread.sleep(5);
+				}
+				currentBuffer = queue.remove();
+				currentBufferPos = 0;
+				return currentBuffer.length > 0;
+			} catch (final InterruptedException ex) {
+				Thread.currentThread().interrupt();
+				throw new IOException("Thread interrupted while reading.", ex); //$NON-NLS-1$
+			}
+		}
 	}
 
 	public LaunchConfigurationStreamProvider(ILaunchConfiguration launchConfig, @Nullable Set<String> launchModes) {
@@ -116,8 +148,8 @@ public boolean equals(@Nullable Object obj) {
 			return true;
 		}
 		return obj instanceof LaunchConfigurationStreamProvider other && //
-			this.launchConfiguration.equals(other.launchConfiguration) && //
-			this.launchModes.equals(other.launchModes);
+				this.launchConfiguration.equals(other.launchConfiguration) && //
+				this.launchModes.equals(other.launchModes);
 	}
 
 	@Override
@@ -147,8 +179,8 @@ public void start() throws IOException {
 		// the IDE when Outline is displayed.
 		boolean statusHandlerToUpdate = disableStatusHandler();
 		try {
-			final var launch = this.launch = this.launchConfiguration.launch(this.launchModes.iterator().next(), new NullProgressMonitor(),
-					false);
+			final var launch = this.launch = this.launchConfiguration.launch(this.launchModes.iterator().next(),
+					new NullProgressMonitor(), false);
 			long initialTimestamp = System.currentTimeMillis();
 			while (launch.getProcesses().length == 0 && System.currentTimeMillis() - initialTimestamp < 5000) {
 				try {
@@ -162,7 +194,7 @@ public void start() throws IOException {
 				final var process = this.process = launch.getProcesses()[0];
 				final var inputStream = this.inputStream = new StreamProxyInputStream(process);
 				final var proxy = process.getStreamsProxy();
-				if(proxy != null) {
+				if (proxy != null) {
 					final var mon = proxy.getOutputStreamMonitor();
 					if (mon != null) {
 						mon.addListener(inputStream);
@@ -178,7 +210,7 @@ public void start() throws IOException {
 					LanguageServerPlugin.logError(ex);
 				}
 				final var errorStream = this.errorStream = new StreamProxyInputStream(process);
-				if(proxy != null) {
+				if (proxy != null) {
 					final var mon = proxy.getErrorStreamMonitor();
 					if (mon != null) {
 						mon.addListener(errorStream);
@@ -187,8 +219,7 @@ public void start() throws IOException {
 			}
 		} catch (Exception e) {
 			LanguageServerPlugin.logError(e);
-		}
-		finally {
+		} finally {
 			if (statusHandlerToUpdate) {
 				setStatusHandler(true);
 			}
@@ -223,7 +254,7 @@ private void setStatusHandler(boolean enabled) {
 
 	@Override
 	public <T> @Nullable T getAdapter(@Nullable Class<T> adapter) {
-		if(adapter == ProcessHandle.class && process != null) {
+		if (adapter == ProcessHandle.class && process != null) {
 			return process.getAdapter(adapter);
 		}
 		return null;