diff --git a/src/main/java/com/taobao/profile/Profiler.java b/src/main/java/com/taobao/profile/Profiler.java
index 0ad4780..c22065d 100644
--- a/src/main/java/com/taobao/profile/Profiler.java
+++ b/src/main/java/com/taobao/profile/Profiler.java
@@ -33,6 +33,14 @@ public class Profiler {
 	public static AtomicInteger instrumentMethodCount = new AtomicInteger(0);
 
 	private final static int size = 65535;
+	/**
+	 * 缓存当前线程对应的采样槽位,避免每次进入方法都竞争全局数组锁
+	 */
+	private static final ThreadLocal<Integer> currentThreadIndex = new ThreadLocal<Integer>();
+	/**
+	 * 缓存当前线程的性能数据对象
+	 */
+	private static final ThreadLocal<ThreadData> currentThreadData = new ThreadLocal<ThreadData>();
 	/**
 	 * 线程数组
 	 */
@@ -43,6 +51,49 @@ public class Profiler {
 	 */
 	public static SlowQueryData[] slowQueryProfile = new SlowQueryData[size];
 
+	/**
+	 * 获取当前线程已存在的性能数据对象
+	 * 
+	 * @param threadIndex
+	 * @return
+	 */
+	private static ThreadData getThreadDataIfPresent(int threadIndex) {
+		Integer cachedIndex = currentThreadIndex.get();
+		ThreadData thrData = currentThreadData.get();
+		if (cachedIndex != null && cachedIndex.intValue() == threadIndex && thrData != null) {
+			return thrData;
+		}
+		thrData = threadProfile[threadIndex];
+		if (thrData != null) {
+			currentThreadIndex.set(threadIndex);
+			currentThreadData.set(thrData);
+		}
+		return thrData;
+	}
+
+	/**
+	 * 获取当前线程的性能数据对象,如不存在则初始化
+	 * 
+	 * @param threadIndex
+	 * @return
+	 */
+	private static ThreadData getOrCreateThreadData(int threadIndex) {
+		ThreadData thrData = getThreadDataIfPresent(threadIndex);
+		if (thrData != null) {
+			return thrData;
+		}
+		synchronized (threadProfile) {
+			thrData = threadProfile[threadIndex];
+			if (thrData == null) {
+				thrData = new ThreadData();
+				threadProfile[threadIndex] = thrData;
+			}
+		}
+		currentThreadIndex.set(threadIndex);
+		currentThreadData.set(thrData);
+		return thrData;
+	}
+
 	/**
 	 * 方法开始时调用,采集开始时间
 	 * 
@@ -65,21 +116,14 @@ public static void Start(int methodId) {
 		}
 		try {
 			int threadIndex = (int) threadId;
-			synchronized (threadProfile) {
-				ThreadData thrData = threadProfile[threadIndex];
-				if (thrData == null) {
-					thrData = new ThreadData();
-					threadProfile[threadIndex] = thrData;
-				}
-
-				synchronized (thrData) {
-					long[] frameData = new long[3];
-					frameData[0] = methodId;
-					frameData[1] = thrData.stackNum;
-					frameData[2] = startTime;
-					thrData.stackFrame.push(frameData);
-					thrData.stackNum++;
-				}
+			ThreadData thrData = getOrCreateThreadData(threadIndex);
+			synchronized (thrData) {
+				long[] frameData = new long[3];
+				frameData[0] = methodId;
+				frameData[1] = thrData.stackNum;
+				frameData[2] = startTime;
+				thrData.stackFrame.push(frameData);
+				thrData.stackNum++;
 			}
 		} catch (Exception e) {
 			e.printStackTrace();
@@ -108,7 +152,7 @@ public static void End(int methodId) {
 		}
 		try {
 			int threadIndex = (int) threadId;
-			ThreadData thrData = threadProfile[threadIndex];
+			ThreadData thrData = getThreadDataIfPresent(threadIndex);
 			if (thrData == null) {
 				return;
 			}
diff --git a/src/main/java/com/taobao/profile/thread/SamplerThread.java b/src/main/java/com/taobao/profile/thread/SamplerThread.java
index e4aa645..e6c0f6a 100644
--- a/src/main/java/com/taobao/profile/thread/SamplerThread.java
+++ b/src/main/java/com/taobao/profile/thread/SamplerThread.java
@@ -55,9 +55,9 @@ public void run() {
 				if (Manager.instance().canDump()) {
 					Date date = new Date();
 					Map<Thread, StackTraceElement[]> map = Thread.getAllStackTraces();
+					StringBuilder sb = new StringBuilder(map.size() * 256);
 					for (Map.Entry<Thread, StackTraceElement[]> entry : map.entrySet()) {
 						Thread thread = entry.getKey();
-						StringBuilder sb = new StringBuilder();
 						sb.append("Thread\t");
 						sb.append(thread.getId());
 						sb.append("\t");
@@ -67,11 +67,13 @@ public void run() {
 						sb.append("\t");
 						sb.append(date);
 						sb.append("\n");
-						fileWriter.append(sb.toString());
 						for (StackTraceElement element : entry.getValue()) {
-							fileWriter.append(element.toString());
-							fileWriter.append("\n");
+							sb.append(element.toString());
+							sb.append("\n");
 						}
+					}
+					if (sb.length() > 0) {
+						fileWriter.append(sb.toString());
 						fileWriter.flushAppend();
 					}
 				}