diff --git a/Makefile b/Makefile
index adc86df..5a0fe7d 100644
--- a/Makefile
+++ b/Makefile
@@ -26,8 +26,6 @@ slowclient: socket_wrapper.o client.c
 .PHONY: clean test
 clean:
 	rm *.o $(Bin)
-	rm $(addprefix client_test/,$(ClientBin))
-	rm $(addprefix server_test/,$(ServerBin))
 
 test:
 	make all
diff --git a/README.md b/README.md
index ff93f02..d3e2622 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,7 @@ For server
 - DEFAULT_WORK_QUEUE_SIZE(server only): 10
 - DEFAULT_MAX_THREAD_NUMBER(server only): 10
 - DEFAULT_RESPONSE_REQUEST(p-server only): 3(-1 is INF)
+- USE_TRACE
 
 For client
 - MUL_CLIENT(second unit)
diff --git a/client.c b/client.c
index 6958711..53c0f0f 100644
--- a/client.c
+++ b/client.c
@@ -13,10 +13,9 @@
 #include <assert.h>
 #include <fcntl.h>
 #include <time.h>
-#include <sys/time.h>
-#include <sys/times.h>
 #include <pthread.h>
 #include "socket_wrapper.h"
+#include "timerhelper.h"
 
 #ifndef DEFAULT_TIMEOUT
 static const int TIMEOUT = 5;
@@ -208,16 +207,6 @@ void init_bench_data(){
         clock_getres(bench.clock_id,&bench.resolution);
     }
 }
-static inline struct timespec timespec_sub(struct timespec a,struct timespec b){
-    struct timespec ret;
-    ret.tv_sec = a.tv_sec - b.tv_sec;
-    ret.tv_nsec = a.tv_nsec - b.tv_nsec;
-    if (ret.tv_nsec < 0){
-        ret.tv_sec--;
-        ret.tv_nsec += 1000000000L;
-    }
-    return ret;
-}
 
 static size_t thread_number_option = 1;
 
diff --git a/server.c b/server.c
index 81ec9eb..f3ec465 100644
--- a/server.c
+++ b/server.c
@@ -16,6 +16,7 @@
 
 #include "socket_wrapper.h"
 #include "simple_circular_buffer.h"
+#include "timerhelper.h"
 
 #ifndef DEFAULT_MAX_LISTEN_SOCKET
 static const int MAX_LISTEN_SOCKET = 16;
@@ -235,13 +236,24 @@ int parse_args(int argc,const char * argv[] , in_port_t * port){
 typedef struct SharedState{
     //empty if less than 0
     queue_struct(int,WORK_QUEUE_SIZE) socks;
+#ifdef USE_TRACE
+    queue_struct(struct timespec,WORK_QUEUE_SIZE) trace_timer;
+#endif
     pthread_mutex_t sock_mutex;
     pthread_cond_t ready;
     //int progress[MAX_THREAD_NUMBER];
 } shared_state_t;
 
+#ifdef USE_TRACE
+enum{
+    Trace_Timer_ID = CLOCK_PROCESS_CPUTIME_ID
+};
+#endif
 void init_shared_state(shared_state_t * state) {
     queue_init(&state->socks);
+#ifdef USE_TRACE
+    queue_init(&state->trace_timer);
+#endif
     pthread_mutex_init(&state->sock_mutex,NULL);
     pthread_cond_init(&state->ready,NULL);
 }
@@ -275,17 +287,32 @@ static shared_state_t globalState;
 void * worker_proc(void * data){
     worker_argument_t * args = (worker_argument_t *)data;
     int fd, csock;
+#ifdef USE_TRACE
+    struct timespec ts,ts_middle,ts_end;
+#endif
     for(;;){
         pthread_mutex_lock(&globalState.sock_mutex);
         while (queue_isempty(&globalState.socks)){
             pthread_cond_wait(&globalState.ready,&globalState.sock_mutex);
         }
         csock = dequeue(&globalState.socks);
+#ifdef USE_TRACE
+        ts = dequeue(&globalState.trace_timer);
+#endif
         pthread_mutex_unlock(&globalState.sock_mutex);
+#ifdef USE_TRACE    
+        clock_gettime(Trace_Timer_ID,&ts_middle);
+#endif
         if((fd = read_request(csock,args->buf,args->bufsize)) > 0){
             send_response(csock,fd,args->buf,args->bufsize);
             close(fd);
         }
+#ifdef USE_TRACE
+        clock_gettime(Trace_Timer_ID,&ts_end);
+        struct timespec tophalf = timespec_sub(ts_middle,ts);
+        struct timespec bottomhelf = timespec_sub(ts_end,ts_middle);
+        fprintf(stderr,"top : %ld ns, bottom : %ld ns\n",tophalf.tv_nsec,bottomhelf.tv_nsec);
+#endif
 
         if(close(csock) < 0)
             perror("csock close error");
@@ -358,6 +385,10 @@ int main(int argc, const char *argv[]){
         char ip_buf[INET_ADDRSTRLEN];
         const char * msg = inet_ntop(AF_INET,&client_addr.sin_addr,ip_buf,sizeof(ip_buf));
         fprintf(stdout,"Connected on : %s:%d\n",msg == NULL ? "(null)" : msg , ntohs(addr.sin_port));
+#ifdef USE_TRACE
+        struct timespec ts;
+        clock_gettime(Trace_Timer_ID, &ts);    
+#endif
         for(;;){
             pthread_mutex_lock(&globalState.sock_mutex);
             if (queue_isfull(&globalState.socks)){
@@ -369,7 +400,12 @@ int main(int argc, const char *argv[]){
 #endif    
                 continue;
             }
-            else enqueue(&globalState.socks,csock);
+            else {
+                enqueue(&globalState.socks,csock);
+#ifdef USE_TRACE
+                enqueue(&globalState.trace_timer,ts);    
+#endif
+            }
             break;
         }
         pthread_mutex_unlock(&globalState.sock_mutex);
diff --git a/timerhelper.h b/timerhelper.h
new file mode 100644
index 0000000..ae90e96
--- /dev/null
+++ b/timerhelper.h
@@ -0,0 +1,16 @@
+#ifndef _TIMERHELPER_H_
+#define _TIMERHELPER_H_
+#include <sys/time.h>
+
+__always_inline struct timespec timespec_sub(struct timespec a,struct timespec b){
+    struct timespec ret;
+    ret.tv_sec = a.tv_sec - b.tv_sec;
+    ret.tv_nsec = a.tv_nsec - b.tv_nsec;
+    if (ret.tv_nsec < 0){
+        ret.tv_sec--;
+        ret.tv_nsec += 1000000000L;
+    }
+    return ret;
+}
+
+#endif
\ No newline at end of file