diff --git a/mace/core/mace.cc b/mace/core/mace.cc
index 83729b79121c90232cc336b9437ed95ed7d3b6e0..3e0d642f8affcdf541d016519d063991636156cc 100644
--- a/mace/core/mace.cc
+++ b/mace/core/mace.cc
@@ -10,7 +10,7 @@
 namespace mace {
 
 ConstTensor::ConstTensor(const std::string &name,
-                         unsigned char *data,
+                         const unsigned char *data,
                          const std::vector<int64_t> &dims,
                          const DataType data_type,
                          uint32_t node_id) :
@@ -23,7 +23,7 @@ ConstTensor::ConstTensor(const std::string &name,
     node_id_(node_id) {}
 
 ConstTensor::ConstTensor(const std::string &name,
-                         unsigned char *data,
+                         const unsigned char *data,
                          const std::vector<int64_t> &dims,
                          const int data_type,
                          uint32_t node_id) :
diff --git a/mace/core/net.cc b/mace/core/net.cc
index 1dcef048cf8b0ec53863da471b23bcf7df74720f..46febc68122d4579cc3d44fada8df2a12f968a58 100644
--- a/mace/core/net.cc
+++ b/mace/core/net.cc
@@ -22,7 +22,7 @@ SimpleNet::SimpleNet(const std::shared_ptr<const OperatorRegistry> op_registry,
                      const NetMode mode)
     :  NetBase(op_registry, net_def, ws, type),
       device_type_(type) {
-  VLOG(1) << "Constructing SimpleNet " << net_def->name();
+  MACE_LATENCY_LOGGER(1, "Constructing SimpleNet ", net_def->name());
   for (int idx = 0; idx < net_def->op_size(); ++idx) {
     const auto &operator_def = net_def->op(idx);
     VLOG(3) << "Creating operator " << operator_def.name() << "("
@@ -41,10 +41,8 @@ bool SimpleNet::Run(RunMetadata *run_metadata) {
   MACE_LATENCY_LOGGER(1, "Running net");
   for (auto iter = operators_.begin(); iter != operators_.end(); ++iter) {
     auto &op = *iter;
-    VLOG(3) << "Running operator " << op->debug_def().name() << "("
-            << op->debug_def().type() << ").";
-    MACE_LATENCY_LOGGER(2, "Running operator ", op->debug_def().name());
-
+    MACE_LATENCY_LOGGER(2, "Running operator ", op->debug_def().name(),
+                        "(", op->debug_def().type(), ")");
     bool future_wait = (device_type_ == DeviceType::OPENCL &&
                         (run_metadata != nullptr ||
                          std::distance(iter, operators_.end()) == 1));
diff --git a/mace/core/workspace.cc b/mace/core/workspace.cc
index 2cf55a3b0548bb350a320f1a04f8196946ccd50f..29491e0fd63aa002892e151b588935083d6f163b 100644
--- a/mace/core/workspace.cc
+++ b/mace/core/workspace.cc
@@ -74,11 +74,11 @@ void Workspace::LoadModelTensor(const NetDef &net_def, DeviceType type) {
   Serializer serializer;
   for (auto &tensor_proto : net_def.tensors()) {
     MACE_LATENCY_LOGGER(2, "Load tensor ", tensor_proto.name());
-    VLOG(3) << "Load tensor: " << tensor_proto.name()
-            << ", with data type: " << tensor_proto.data_type()
-            << ", has shape: "
+    VLOG(3) << "Tensor name: " << tensor_proto.name()
+            << ", data type: " << tensor_proto.data_type()
+            << ", shape: "
             << MakeString(std::vector<index_t>(tensor_proto.dims().begin(),
-                                          tensor_proto.dims().end()));
+                                               tensor_proto.dims().end()));
     tensor_map_[tensor_proto.name()] =
         serializer.Deserialize(tensor_proto, type);
   }
diff --git a/mace/public/mace.h b/mace/public/mace.h
index ab91e4c7592e862f2abbc540b5dca0884417a3e1..591987cb9eb0740b790dffb8f2b519adb17e887f 100644
--- a/mace/public/mace.h
+++ b/mace/public/mace.h
@@ -73,12 +73,12 @@ enum DataType {
 class ConstTensor {
  public:
   ConstTensor(const std::string &name,
-              unsigned char *data,
+              const unsigned char *data,
               const std::vector<int64_t> &dims,
               const DataType data_type = DT_FLOAT,
               uint32_t node_id = 0);
   ConstTensor(const std::string &name,
-              unsigned char *data,
+              const unsigned char *data,
               const std::vector<int64_t> &dims,
               const int data_type,
               uint32_t node_id = 0);
diff --git a/mace/utils/logging.h b/mace/utils/logging.h
index 6dc5658c40da3f85d210cf56dde530dbfcc2239c..592831580f850a22adac6d50e2ddfb3cf0bdbf0b 100644
--- a/mace/utils/logging.h
+++ b/mace/utils/logging.h
@@ -113,6 +113,7 @@ class LatencyLogger {
       : vlog_level_(vlog_level), message_(message) {
     if (VLOG_IS_ON(vlog_level_)) {
       start_micros_ = NowMicros();
+      VLOG(vlog_level_) << message_ << " started";
     }
   }
   ~LatencyLogger() {
diff --git a/tools/export_lib.sh b/tools/export_lib.sh
index 119dfa1513025b337503d99f85ce82f4b7e023e6..a178c118f85a4843b534559445f5cf1bbde80c80 100755
--- a/tools/export_lib.sh
+++ b/tools/export_lib.sh
@@ -161,8 +161,10 @@ rm -rf ${EXPORT_LIB_DIR}
 mkdir -p ${EXPORT_LIB_DIR}
 
 cp ${MACE_SOURCE_DIR}/mace/public/*.h ${EXPORT_INCLUDE_DIR}/mace/public/ || exit 1
-# utils is noti part of public API
-cp ${MACE_SOURCE_DIR}/mace/utils/*.h ${EXPORT_INCLUDE_DIR}/mace/utils/ || exit 1
+# utils is not part of public API
+cp ${MACE_SOURCE_DIR}/mace/utils/env_time.h ${EXPORT_INCLUDE_DIR}/mace/utils/ || exit 1
+cp ${MACE_SOURCE_DIR}/mace/utils/logging.h ${EXPORT_INCLUDE_DIR}/mace/utils/ || exit 1
+cp ${MACE_SOURCE_DIR}/mace/utils/string_util.h ${EXPORT_INCLUDE_DIR}/mace/utils/ || exit 1
 cp ${LIBMACE_TEMP_DIR}/libmace.a ${LIBMACE_TEMP_DIR}/libmace_dev.a ${LIBMACE_TEMP_DIR}/libmace_prod.a ${EXPORT_LIB_DIR}/ || exit 1
 
 echo "Step 6: Remove temporary file"