diff --git a/mqtt_jmeter/src/main/java/net/xmeter/Util.java b/mqtt_jmeter/src/main/java/net/xmeter/Util.java
index 8fca1aa..85d61b1 100644
--- a/mqtt_jmeter/src/main/java/net/xmeter/Util.java
+++ b/mqtt_jmeter/src/main/java/net/xmeter/Util.java
@@ -5,6 +5,7 @@
 import java.io.InputStream;
 import java.security.KeyStore;
 import java.security.SecureRandom;
+import java.util.Random;
 import java.util.UUID;
 import java.util.logging.Logger;
 
@@ -18,9 +19,23 @@
 
 public class Util implements Constants {
 	
-	private static SecureRandom random = new SecureRandom();
+	private static Random random = new Random();
     private static char[] seeds = "abcdefghijklmnopqrstuvwxmy0123456789".toCharArray();
     private static final Logger logger = Logger.getLogger(Util.class.getCanonicalName());
+    
+    private static String[] longChunks = new String[16];
+    private static final int PAYLOAD_CHUNK_SIZE = 4096;
+    
+    static {
+    	for (int i = 0; i < longChunks.length; i++) {
+    		StringBuffer res = new StringBuffer();
+    		for(int j = 0; j < 4096; j++) {
+    			res.append(seeds[random.nextInt(seeds.length - 1)]);
+    		}
+    		longChunks[i] = res.toString();
+    	}
+		
+    }
 
 	public static String generateClientId(String prefix) {
 		int leng = prefix.length();
@@ -37,12 +52,12 @@ public static String generateClientId(String prefix) {
 
 	public static SSLContext getContext(AbstractMQTTSampler sampler) throws Exception {
 		if (!sampler.isDualSSLAuth()) {
-			logger.info("Configured with non-dual SSL.");
+			logger.fine("Configured with non-dual SSL.");
 			SSLContext sslContext = SSLContext.getInstance("TLSv1.2");
 			sslContext.init(null, new TrustManager[] {new AcceptAllTrustManager()}, new SecureRandom());
 			return sslContext;
 		} else {
-			logger.info("Configured with dual SSL, trying to load client certification.");
+			logger.fine("Configured with dual SSL, trying to load client certification.");
 //			String KEYSTORE_PASS = sampler.getKeyStorePassword();
 			String CLIENTCERT_PASS = sampler.getClientCertPassword();
 
@@ -95,11 +110,40 @@ private static File getFilePath(String filePath) {
 
 	public static String generatePayload(int size) {
 		StringBuffer res = new StringBuffer();
-		for(int i = 0; i < size; i++) {
-			res.append(seeds[random.nextInt(seeds.length - 1)]);
+		if (size <= PAYLOAD_CHUNK_SIZE) {
+			for(int i = 0; i < size; i++) {
+				res.append(seeds[random.nextInt(seeds.length - 1)]);
+			}
+		} else {
+			int block = size / PAYLOAD_CHUNK_SIZE;
+			int remainSize = size % PAYLOAD_CHUNK_SIZE;
+			int[] indices = randomIndices(longChunks.length);
+			for(int i=0; i<block; i++) {
+				int ind = block % 10;
+				res.append(longChunks[indices[ind]]);
+			}
+			res.append(randomChunkPiece(remainSize));
 		}
 		return res.toString();
 	}
+	
+	private static int[] randomIndices(int length) {
+		int[] indices = new int[10];
+		int val = random.nextInt(Integer.MAX_VALUE);
+		String str = String.format("%010d", val);
+		for (int i = 0; i < indices.length; i++) {
+			int intVal = Character.getNumericValue(str.charAt(i)) % length;
+			indices[i] = intVal;
+		}
+		return indices;
+	}
+	
+	private static String randomChunkPiece(int remainSize) {
+		int start = random.nextInt(PAYLOAD_CHUNK_SIZE - remainSize + 1);
+		int end = start + remainSize;
+		int randomInd = random.nextInt(longChunks.length);
+		return longChunks[randomInd].substring(start, end);
+	}
 
 	public static boolean isSecureProtocol(String protocol) {
 		return SSL_PROTOCOL.equals(protocol) || WSS_PROTOCOL.equals(protocol);
diff --git a/mqtt_jmeter/src/main/java/net/xmeter/samplers/PubSampler.java b/mqtt_jmeter/src/main/java/net/xmeter/samplers/PubSampler.java
index fb86b04..1598b1f 100644
--- a/mqtt_jmeter/src/main/java/net/xmeter/samplers/PubSampler.java
+++ b/mqtt_jmeter/src/main/java/net/xmeter/samplers/PubSampler.java
@@ -143,8 +143,7 @@ public SampleResult sample(Entry arg0) {
 				System.arraycopy(timePrefix, 0, toSend, 0, timePrefix.length);
 				System.arraycopy(tmp, 0, toSend, timePrefix.length , tmp.length);
 			} else {
-				toSend = new byte[tmp.length];
-				System.arraycopy(tmp, 0, toSend, 0 , tmp.length);
+				toSend = tmp;
 			}
 			
 			result.sampleStart();
@@ -155,7 +154,12 @@ public SampleResult sample(Entry arg0) {
 			MQTTPubResult pubResult = connection.publish(topicName, toSend, qos_enum, retainedMsg);
 			
 			result.sampleEnd();
-			result.setSamplerData(new String(toSend));
+			//only keep the first 1024 characters in sampler data
+			if (toSend.length <= 1024) {
+				result.setSamplerData(new String(toSend));
+			} else {
+				result.setSamplerData(new String(toSend).substring(0, 1024) + "...");
+			}
 			result.setSentBytes(toSend.length);
 			result.setLatency(result.getEndTime() - result.getStartTime());
 			result.setSuccessful(pubResult.isSuccessful());
@@ -169,8 +173,8 @@ public SampleResult sample(Entry arg0) {
 				result.setResponseMessage(MessageFormat.format("Publish failed for connection {0}.", connection));
 				result.setResponseData(MessageFormat.format("Client [{0}] publish failed: {1}", (clientId == null ? "null" : clientId), pubResult.getError().orElse("")).getBytes());
 				result.setResponseCode("501");
-				logger.info(MessageFormat.format("** [clientId: {0}, topic: {1}, payload: {2}] Publish failed for connection {3}.", (clientId == null ? "null" : clientId),
-						topicName, new String(toSend), connection));
+				logger.info(MessageFormat.format("** [clientId: {0}, topic: {1}] Publish failed for connection {2}.", (clientId == null ? "null" : clientId),
+						topicName, connection));
 				pubResult.getError().ifPresent(logger::info);
 			}
 		} catch (Exception ex) {