diff --git a/src/brpc/event_dispatcher.cpp b/src/brpc/event_dispatcher.cpp
index 53495ea6d7..a8f1b9dc0e 100644
--- a/src/brpc/event_dispatcher.cpp
+++ b/src/brpc/event_dispatcher.cpp
@@ -21,9 +21,9 @@
 #include "butil/fd_utility.h"                         // make_close_on_exec
 #include "butil/logging.h"                            // LOG
 #include "butil/third_party/murmurhash3/murmurhash3.h"// fmix32
+#include "bvar/latency_recorder.h"                    // bvar::LatencyRecorder
 #include "bthread/bthread.h"                          // bthread_start_background
 #include "brpc/event_dispatcher.h"
-#include "brpc/reloadable_flags.h"
 
 DECLARE_int32(task_group_ntags);
 
@@ -37,6 +37,8 @@ DEFINE_bool(usercode_in_coroutine, false,
             "User's callback are run in coroutine, no bthread or pthread blocking call");
 
 static EventDispatcher* g_edisp = NULL;
+static bvar::LatencyRecorder* g_edisp_read_lantency = NULL;
+static bvar::LatencyRecorder* g_edisp_write_lantency = NULL;
 static pthread_once_t g_edisp_once = PTHREAD_ONCE_INIT;
 
 static void StopAndJoinGlobalDispatchers() {
@@ -46,8 +48,13 @@ static void StopAndJoinGlobalDispatchers() {
             g_edisp[i * FLAGS_event_dispatcher_num + j].Join();
         }
     }
+    delete g_edisp_read_lantency;
+    delete g_edisp_write_lantency;
 }
 void InitializeGlobalDispatchers() {
+    g_edisp_read_lantency = new bvar::LatencyRecorder("event_dispatcher_read_latency");
+    g_edisp_write_lantency = new bvar::LatencyRecorder("event_dispatcher_write_latency");
+
     g_edisp = new EventDispatcher[FLAGS_task_group_ntags * FLAGS_event_dispatcher_num];
     for (int i = 0; i < FLAGS_task_group_ntags; ++i) {
         for (int j = 0; j < FLAGS_event_dispatcher_num; ++j) {
diff --git a/src/brpc/event_dispatcher_epoll.cpp b/src/brpc/event_dispatcher_epoll.cpp
index 64717b1623..0ea404fff6 100644
--- a/src/brpc/event_dispatcher_epoll.cpp
+++ b/src/brpc/event_dispatcher_epoll.cpp
@@ -222,14 +222,18 @@ void EventDispatcher::Run() {
                 || (e[i].events & has_epollrdhup)
 #endif
                 ) {
+                int64_t start_ns = butil::cpuwide_time_ns();
                 // We don't care about the return value.
                 CallInputEventCallback(e[i].data.u64, e[i].events, _thread_attr);
+                (*g_edisp_read_lantency) << (butil::cpuwide_time_ns() - start_ns);
             }
         }
         for (int i = 0; i < n; ++i) {
             if (e[i].events & (EPOLLOUT | EPOLLERR | EPOLLHUP)) {
+                int64_t start_ns = butil::cpuwide_time_ns();
                 // We don't care about the return value.
                 CallOutputEventCallback(e[i].data.u64, e[i].events, _thread_attr);
+                (*g_edisp_write_lantency) << (butil::cpuwide_time_ns() - start_ns);
             }
         }
     }
diff --git a/src/brpc/event_dispatcher_kqueue.cpp b/src/brpc/event_dispatcher_kqueue.cpp
index 97ad29bba6..a179048604 100644
--- a/src/brpc/event_dispatcher_kqueue.cpp
+++ b/src/brpc/event_dispatcher_kqueue.cpp
@@ -205,16 +205,20 @@ void EventDispatcher::Run() {
         }
         for (int i = 0; i < n; ++i) {
             if ((e[i].flags & EV_ERROR) || e[i].filter == EVFILT_READ) {
+                int64_t start_ns = butil::cpuwide_time_ns();
                 // We don't care about the return value.
                 CallInputEventCallback((IOEventDataId)e[i].udata,
                                        e[i].filter, _thread_attr);
+                (*g_edisp_read_lantency) << (butil::cpuwide_time_ns() - start_ns);
             }
         }
         for (int i = 0; i < n; ++i) {
             if ((e[i].flags & EV_ERROR) || e[i].filter == EVFILT_WRITE) {
+                int64_t start_ns = butil::cpuwide_time_ns();
                 // We don't care about the return value.
                 CallOutputEventCallback((IOEventDataId)e[i].udata,
                                         e[i].filter, _thread_attr);
+                (*g_edisp_write_lantency) << (butil::cpuwide_time_ns() - start_ns);
             }
         }
     }
diff --git a/test/bthread_unittest.cpp b/test/bthread_unittest.cpp
index 0286db9904..57f4fc82bd 100644
--- a/test/bthread_unittest.cpp
+++ b/test/bthread_unittest.cpp
@@ -111,6 +111,7 @@ TEST_F(BthreadTest, call_bthread_functions_before_tls_created) {
     ASSERT_EQ(0UL, bthread_self());
 }
 
+butil::atomic<bool> start(false);
 butil::atomic<bool> stop(false);
 
 void* sleep_for_awhile(void* arg) {
@@ -128,6 +129,7 @@ void* just_exit(void* arg) {
 }
 
 void* repeated_sleep(void* arg) {
+    start = true;
     for (size_t i = 0; !stop; ++i) {
         LOG(INFO) << "repeated_sleep(" << arg << ") i=" << i;
         bthread_usleep(1000000L);
@@ -136,6 +138,7 @@ void* repeated_sleep(void* arg) {
 }
 
 void* spin_and_log(void* arg) {
+    start = true;
     // This thread never yields CPU.
     butil::EveryManyUS every_1s(1000000L);
     size_t i = 0;
@@ -620,10 +623,13 @@ TEST_F(BthreadTest, yield_single_thread) {
 
 #ifdef BRPC_BTHREAD_TRACER
 TEST_F(BthreadTest, trace) {
+    start = false;
     stop = false;
     bthread_t th;
     ASSERT_EQ(0, bthread_start_urgent(&th, NULL, spin_and_log, (void*)1));
-    usleep(100 * 1000);
+    while (!start) {
+        usleep(10 * 1000);
+    }
     bthread::FLAGS_enable_fast_unwind = false;
     std::string st = bthread::stack_trace(th);
     LOG(INFO) << "fast_unwind spin_and_log stack trace:\n" << st;
@@ -636,9 +642,12 @@ TEST_F(BthreadTest, trace) {
     stop = true;
     ASSERT_EQ(0, bthread_join(th, NULL));
 
+    start = false;
     stop = false;
     ASSERT_EQ(0, bthread_start_urgent(&th, NULL, repeated_sleep, (void*)1));
-    usleep(100 * 1000);
+    while (!start) {
+        usleep(10 * 1000);
+    }
     bthread::FLAGS_enable_fast_unwind = false;
     st = bthread::stack_trace(th);
     LOG(INFO) << "fast_unwind repeated_sleep stack trace:\n" << st;