diff a/src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java b/src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java
--- a/src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java
+++ b/src/jdk.incubator.foreign/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java
@@ -30,10 +30,11 @@
 import jdk.incubator.foreign.SequenceLayout;
 import jdk.internal.access.JavaNioAccess;
 import jdk.internal.access.SharedSecrets;
 import jdk.internal.access.foreign.MemorySegmentProxy;
 import jdk.internal.access.foreign.UnmapperProxy;
+import jdk.internal.misc.Unsafe;
 import jdk.internal.vm.annotation.ForceInline;
 import sun.security.action.GetPropertyAction;
 
 import java.lang.invoke.VarHandle;
 import java.nio.ByteBuffer;
@@ -53,10 +54,12 @@
  * are defined for each memory segment kind, see {@link NativeMemorySegmentImpl}, {@link HeapMemorySegmentImpl} and
  * {@link MappedMemorySegmentImpl}.
  */
 public abstract class AbstractMemorySegmentImpl implements MemorySegment, MemorySegmentProxy {
 
+    private static final Unsafe UNSAFE = Unsafe.getUnsafe();
+
     private static final boolean enableSmallSegments =
             Boolean.parseBoolean(GetPropertyAction.privilegedGetProperty("jdk.incubator.foreign.SmallSegments", "true"));
 
     final static int ACCESS_MASK = READ | WRITE | CLOSE | ACQUIRE | HANDOFF;
     final static int FIRST_RESERVED_FLAG = 1 << 16; // upper 16 bits are reserved
@@ -111,10 +114,19 @@
         }
         return (Spliterator<S>)new SegmentSplitter(sequenceLayout.elementLayout().byteSize(), sequenceLayout.elementCount().getAsLong(),
                 (AbstractMemorySegmentImpl)segment.withAccessModes(segment.accessModes() & ~CLOSE));
     }
 
+    public static void fill(MemorySegment segment, byte value) {
+        AbstractMemorySegmentImpl segmentImpl = (AbstractMemorySegmentImpl) segment;
+        segmentImpl.checkValidState();
+        if (!segmentImpl.isSet(WRITE)) {
+            throw segmentImpl.unsupportedAccessMode(WRITE);
+        }
+        UNSAFE.setMemory(segmentImpl.base(), segmentImpl.min(), segmentImpl.length, value);
+    }
+
     @Override
     @ForceInline
     public final MemoryAddress baseAddress() {
         return new MemoryAddressImpl(this, 0);
     }