diff --git a/cpp/unittest/db/mem_test.cpp b/cpp/unittest/db/mem_test.cpp
index 2f6952c79d6cdaf5afb0621ab415146683d6ffcf..17d87030cd3fed6e3e827d412acc61640e030fe7 100644
--- a/cpp/unittest/db/mem_test.cpp
+++ b/cpp/unittest/db/mem_test.cpp
@@ -273,7 +273,7 @@ TEST_F(NewMemManagerTest, INSERT_TEST) {
 
     int insert_loop = 20;
     for (int i = 0; i < insert_loop; ++i) {
-        int64_t nb = 409600;
+        int64_t nb = 40960;
         std::vector<float> xb;
         BuildVectors(nb, xb);
         engine::IDNumbers vector_ids;
@@ -308,7 +308,7 @@ TEST_F(NewMemManagerTest, CONCURRENT_INSERT_SEARCH_TEST) {
     engine::IDNumbers vector_ids;
     engine::IDNumbers target_ids;
 
-    int64_t nb = 409600;
+    int64_t nb = 40960;
     std::vector<float> xb;
     BuildVectors(nb, xb);