diff --git a/deploy/cpp_infer/src/ocr_det.cpp b/deploy/cpp_infer/src/ocr_det.cpp
index a935003bb453bcb13da2717eae642f1f09addf37..bf94abce236853410c15434d494058be03a62a81 100644
--- a/deploy/cpp_infer/src/ocr_det.cpp
+++ b/deploy/cpp_infer/src/ocr_det.cpp
@@ -26,6 +26,7 @@ void DBDetector::LoadModel(const std::string &model_dir) {
     config.DisableGpu();
     if (this->use_mkldnn_) {
       config.EnableMKLDNN();
+      // cache 10 different shapes for mkldnn to avoid memory leak
       config.SetMkldnnCacheCapacity(10);
     }
     config.SetCpuMathLibraryNumThreads(this->cpu_math_library_num_threads_);
diff --git a/deploy/cpp_infer/src/ocr_rec.cpp b/deploy/cpp_infer/src/ocr_rec.cpp
index 9d71d8c4553c280fb67022d2054680e93b767153..b997d8291a64f9b6042bce648bcd358e34d55a95 100644
--- a/deploy/cpp_infer/src/ocr_rec.cpp
+++ b/deploy/cpp_infer/src/ocr_rec.cpp
@@ -126,6 +126,7 @@ void CRNNRecognizer::LoadModel(const std::string &model_dir) {
     config.DisableGpu();
     if (this->use_mkldnn_) {
       config.EnableMKLDNN();
+      // cache 10 different shapes for mkldnn to avoid memory leak
       config.SetMkldnnCacheCapacity(10);
     }
     config.SetCpuMathLibraryNumThreads(this->cpu_math_library_num_threads_);
diff --git a/deploy/cpp_infer/tools/config.txt b/deploy/cpp_infer/tools/config.txt
index 40beea3a2e6f0260a42202d6411ffb10907bf871..6c53f29eeb310677815d106d3e0ae39fb03bc2e2 100644
--- a/deploy/cpp_infer/tools/config.txt
+++ b/deploy/cpp_infer/tools/config.txt
@@ -3,7 +3,7 @@ use_gpu  0
 gpu_id  0
 gpu_mem  4000
 cpu_math_library_num_threads  10
-use_mkldnn 0
+use_mkldnn 1
 use_zero_copy_run 1
 
 # det config
diff --git a/tools/infer/utility.py b/tools/infer/utility.py
index 1d07f62f206ca2c250e340921e862bbccd5382b2..3e1f07b8a7127e64a994c34d296c945ad1cafd0a 100755
--- a/tools/infer/utility.py
+++ b/tools/infer/utility.py
@@ -101,6 +101,7 @@ def create_predictor(args, mode):
         config.disable_gpu()
         config.set_cpu_math_library_num_threads(6)
         if args.enable_mkldnn:
+            # cache 10 different shapes for mkldnn to avoid memory leak
             config.set_mkldnn_cache_capacity(10)
             config.enable_mkldnn()