diff --git a/.circleci/config.yml b/.circleci/config.yml
index 00f84b0a..0e9d75ae 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -8,7 +8,7 @@ executors:
         environment:
           CXX: g++
           BUILD_FLAGS: -j
-          CTEST_FLAGS: -j --output-on-failure
+          CTEST_FLAGS: -j4 --output-on-failure
 
   gcc8:
     docker:
@@ -16,7 +16,7 @@ executors:
         environment:
           CXX: g++
           BUILD_FLAGS: -j
-          CTEST_FLAGS: -j --output-on-failure
+          CTEST_FLAGS: -j4 --output-on-failure
 
   gcc9:
     docker:
@@ -24,7 +24,7 @@ executors:
         environment:
           CXX: g++
           BUILD_FLAGS: -j
-          CTEST_FLAGS: -j --output-on-failure
+          CTEST_FLAGS: -j4 --output-on-failure
 
   clang6:
     docker:
@@ -32,7 +32,7 @@ executors:
         environment:
           CXX: clang++-6.0
           BUILD_FLAGS: -j
-          CTEST_FLAGS: -j --output-on-failure
+          CTEST_FLAGS: -j4 --output-on-failure
                 
 # Reusable test commands (and initializer for clang 6)
 commands:
diff --git a/.drone.yml b/.drone.yml
index 80eca218..18ae4224 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -231,7 +231,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ctest -j --output-on-failure -E checkperf
+    - ctest -j4 --output-on-failure -E checkperf
 ---
 kind: pipeline
 name: amd64_clang_cmake_no_exceptions
@@ -254,7 +254,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ctest -j --output-on-failure -E checkperf
+    - ctest -j4 --output-on-failure -E checkperf
 ---
 kind: pipeline
 name: amd64_clang_cmake_static
@@ -277,7 +277,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ctest -j --output-on-failure -E checkperf
+    - ctest -j4 --output-on-failure -E checkperf
 ---
 kind: pipeline
 name: amd64_gcc_cmake_static
@@ -300,7 +300,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ctest -j --output-on-failure -E checkperf
+    - ctest -j4 --output-on-failure -E checkperf
 ---
 kind: pipeline
 name: amd64_gcc_cmake_dynamic
@@ -323,7 +323,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ctest -j --output-on-failure -E checkperf
+    - ctest -j4 --output-on-failure -E checkperf
 ---
 kind: pipeline
 name: arm64_clang_cmake_dynamic
@@ -346,7 +346,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ctest -j --output-on-failure -E checkperf
+    - ctest -j4 --output-on-failure -E checkperf
 ---
 kind: pipeline
 name: arm64_gcc_cmake_dynamic
@@ -369,7 +369,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ctest -j --output-on-failure -E checkperf
+    - ctest -j4 --output-on-failure -E checkperf
 ---
 kind: pipeline
 name: arm64_clang_cmake_static
@@ -392,7 +392,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ctest -j --output-on-failure -E checkperf
+    - ctest -j4 --output-on-failure -E checkperf
 ---
 kind: pipeline
 name: arm64_gcc_cmake_static
@@ -415,7 +415,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ctest -j --output-on-failure -E checkperf
+    - ctest -j4 --output-on-failure -E checkperf
 
 ---
 kind: pipeline
@@ -439,7 +439,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ASAN_OPTIONS="detect_leaks=0" ctest -j --output-on-failure -E checkperf
+    - ASAN_OPTIONS="detect_leaks=0" ctest -j4 --output-on-failure -E checkperf
 ---
 kind: pipeline
 name: arm64_gcc_cmake_sanitize
@@ -462,7 +462,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ASAN_OPTIONS="detect_leaks=0" ctest -j --output-on-failure -E checkperf
+    - ASAN_OPTIONS="detect_leaks=0" ctest -j4 --output-on-failure -E checkperf
 
 ---
 kind: pipeline
@@ -486,7 +486,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ASAN_OPTIONS="detect_leaks=0" ctest -j --output-on-failure -E checkperf
+    - ASAN_OPTIONS="detect_leaks=0" ctest -j4 --output-on-failure -E checkperf
 ---
 kind: pipeline
 name: amd64_gcc_cmake_sanitize
@@ -509,7 +509,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ASAN_OPTIONS="detect_leaks=0" ctest -j --output-on-failure -E checkperf
+    - ASAN_OPTIONS="detect_leaks=0" ctest -j4 --output-on-failure -E checkperf
 
 ---
 kind: pipeline
@@ -533,7 +533,7 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ASAN_OPTIONS="detect_leaks=0" ctest -j --output-on-failure -E checkperf
+    - ASAN_OPTIONS="detect_leaks=0" ctest -j4 --output-on-failure -E checkperf
 ---
 kind: pipeline
 name: amd64_gcc_cmake_sanitize_noavx
@@ -556,4 +556,4 @@ steps:
     - mkdir build && cd build
     - cmake $CMAKE_FLAGS ..
     - make -j
-    - ASAN_OPTIONS="detect_leaks=0" ctest -j --output-on-failure -E checkperf
+    - ASAN_OPTIONS="detect_leaks=0" ctest -j4 --output-on-failure -E checkperf
diff --git a/benchmark/CMakeLists.txt b/benchmark/CMakeLists.txt
index 647eb4a3..bc942c7b 100644
--- a/benchmark/CMakeLists.txt
+++ b/benchmark/CMakeLists.txt
@@ -43,5 +43,7 @@ if (NOT MSVC)
       CHECKPERF_DIR=${CMAKE_CURRENT_BINARY_DIR}/simdjson-master
       CHECKPERF_CMAKECACHE=${SIMDJSON_USER_CMAKECACHE}
       bash ${CMAKE_CURRENT_SOURCE_DIR}/checkperf.sh ${PROJECT_SOURCE_DIR}/jsonexamples/twitter.json)
+  set_property(TEST checkperf APPEND PROPERTY LABELS per_implementation)
   set_property(TEST checkperf APPEND PROPERTY DEPENDS parse perfdiff ${SIMDJSON_USER_CMAKECACHE})
+  set_property(TEST checkperf PROPERTY RUN_SERIAL TRUE)
 endif()