diff --git a/paddle/fluid/framework/threadpool.cc b/paddle/fluid/framework/threadpool.cc
index 0a8377cc4794be29af255067517d9c6841aea108..109c2c745c68756de5e1e4384bd8c717d74d158a 100644
--- a/paddle/fluid/framework/threadpool.cc
+++ b/paddle/fluid/framework/threadpool.cc
@@ -14,8 +14,12 @@
 
 #include "paddle/fluid/framework/threadpool.h"
 
+#include "gflags/gflags.h"
 #include "paddle/fluid/platform/enforce.h"
 
+DEFINE_int32(io_threadpool_size, 100,
+             "number of threads used for doing IO, default 100");
+
 namespace paddle {
 namespace framework {
 
@@ -94,15 +98,15 @@ void ThreadPool::TaskLoop() {
 std::unique_ptr<ThreadPool> MultiStreamThreadPool::io_threadpool_(nullptr);
 std::once_flag MultiStreamThreadPool::io_init_flag_;
 
-MultiStreamThreadPool* MultiStreamThreadPool::GetInstanceIO() {
+ThreadPool* MultiStreamThreadPool::GetInstanceIO() {
   std::call_once(io_init_flag_, &MultiStreamThreadPool::InitIO);
-  return static_cast<MultiStreamThreadPool*>(io_threadpool_.get());
+  return io_threadpool_.get();
 }
 
 void MultiStreamThreadPool::InitIO() {
   if (io_threadpool_.get() == nullptr) {
     // TODO(typhoonzero1986): make this configurable
-    io_threadpool_.reset(new ThreadPool(100));
+    io_threadpool_.reset(new ThreadPool(FLAGS_io_threadpool_size));
   }
 }
 
diff --git a/paddle/fluid/framework/threadpool.h b/paddle/fluid/framework/threadpool.h
index 0a60488d9f629c253bf66f1704fc4cde9e9b65a0..1cc058834c0f4313766773373719a8825f4285b9 100644
--- a/paddle/fluid/framework/threadpool.h
+++ b/paddle/fluid/framework/threadpool.h
@@ -14,12 +14,12 @@ limitations under the License. */
 
 #pragma once
 
-#include <condition_variable>
+#include <condition_variable>  // NOLINT
 #include <functional>
-#include <future>
-#include <mutex>
+#include <future>  // NOLINT
+#include <mutex>   // NOLINT
 #include <queue>
-#include <thread>
+#include <thread>  // NOLINT
 #include <vector>
 #include "glog/logging.h"
 #include "paddle/fluid/platform/enforce.h"
@@ -137,7 +137,7 @@ class ThreadPool {
 
 class MultiStreamThreadPool : ThreadPool {
  public:
-  static MultiStreamThreadPool* GetInstanceIO();
+  static ThreadPool* GetInstanceIO();
   static void InitIO();
 
  private:
diff --git a/paddle/fluid/operators/detail/grpc_server.cc b/paddle/fluid/operators/detail/grpc_server.cc
index d5fc163bc25409e0607b149b61c6266b38119d9d..36dad5dd43a6a0ab57633034cc45b6261c10b3fd 100644
--- a/paddle/fluid/operators/detail/grpc_server.cc
+++ b/paddle/fluid/operators/detail/grpc_server.cc
@@ -216,10 +216,10 @@ void AsyncGRPCServer::RunSyncUpdate() {
   std::function<void()> prefetch_register =
       std::bind(&AsyncGRPCServer::TryToRegisterNewPrefetchOne, this);
 
+  // TODO(wuyi): Run these "HandleRequest" in thread pool
   t_send_.reset(
       new std::thread(std::bind(&AsyncGRPCServer::HandleRequest, this,
                                 cq_send_.get(), "cq_send", send_register)));
-
   t_get_.reset(
       new std::thread(std::bind(&AsyncGRPCServer::HandleRequest, this,
                                 cq_get_.get(), "cq_get", get_register)));
diff --git a/python/paddle/fluid/tests/book/test_recognize_digits.py b/python/paddle/fluid/tests/book/test_recognize_digits.py
index e4997b4069f60ff4382b4254bc026ae8ae29b345..5ec6890c1b0dabd2804a92071b63c9610299e67c 100644
--- a/python/paddle/fluid/tests/book/test_recognize_digits.py
+++ b/python/paddle/fluid/tests/book/test_recognize_digits.py
@@ -157,7 +157,6 @@ def train(nn_type,
         for ip in pserver_ips.split(","):
             eplist.append(':'.join([ip, port]))
         pserver_endpoints = ",".join(eplist)  # ip:port,ip:port...
-        pserver_endpoints = os.getenv("PSERVERS")
         trainers = int(os.getenv("TRAINERS"))
         current_endpoint = os.getenv("POD_IP") + ":" + port
         trainer_id = int(os.getenv("PADDLE_INIT_TRAINER_ID"))