diff --git a/ci/.gitlab-ci.yml b/ci/.gitlab-ci.yml
index 095e064..471f028 100644
--- a/ci/.gitlab-ci.yml
+++ b/ci/.gitlab-ci.yml
@@ -86,6 +86,8 @@ piglit - gl host:
              bash -c "/virglrenderer/ci/run_tests.sh --piglit-gl"
              2>&1 | tee results/docker_test_log.txt
     - echo "\n\n"
+  only:
+    - merge_requests
 
 piglit - gles host:
   stage: test
@@ -107,6 +109,8 @@ piglit - gles host:
              bash -c "/virglrenderer/ci/run_tests.sh --piglit-gles"
              2>&1 | tee results/docker_test_log.txt
     - echo "\n\n"
+  only:
+    - merge_requests
 
   artifacts:
     when: always
@@ -133,6 +137,8 @@ cts - gl host:
              bash -c "/virglrenderer/ci/run_tests.sh --deqp-gl"
              2>&1 | tee results/docker_test_log.txt
     - echo "\n\n"
+  only:
+    - merge_requests
 
   artifacts:
     when: always
@@ -159,6 +165,8 @@ cts - gles host:
              bash -c "/virglrenderer/ci/run_tests.sh --deqp-gles"
              2>&1 | tee results/docker_test_log.txt
     - echo "\n\n"
+  only:
+    - merge_requests
 
   artifacts:
     when: always
@@ -185,6 +193,8 @@ unreliable tests:
              bash -c "/virglrenderer/ci/run_tests.sh --deqp-gl-unreliable --deqp-gles-unreliable --piglit-gl-unreliable --piglit-gles-unreliable || true"
              2>&1 | tee results/docker_test_log.txt
     - echo "\n\n"
+  only:
+    - merge_requests
 
   artifacts:
     when: always
diff --git a/ci/run_test_suite.sh b/ci/run_test_suite.sh
index 4c927e4..4e25379 100755
--- a/ci/run_test_suite.sh
+++ b/ci/run_test_suite.sh
@@ -7,7 +7,7 @@ trap "{ rm -f $TMP_TEST_FILE; }" EXIT
 
 TESTS=""
 BACKENDS=""
-NUM_THREADS=$(expr $(expr $(nproc) + 2) / 3)
+NUM_THREADS=${NUM_THREADS:-$(expr $(expr $(nproc) / 8) + 1)}
 
 COMPARE_BACKENDS=0
 COMPARE_PREVIOUS=0
diff --git a/ci/run_tests.sh b/ci/run_tests.sh
index 4c1cbfb..338534f 100755
--- a/ci/run_tests.sh
+++ b/ci/run_tests.sh
@@ -6,7 +6,7 @@ run_setup()
 
    # Let .gitlab-ci or local ci runner set
    # desired thread count
-   NUM_THREADS=${NUM_THREADS:-"$(nproc)"}
+   NUM_THREADS=${NUM_THREADS:-$(expr $(expr $(nproc) / 8) + 1)}
    export NUM_THREADS
    echo "Using $NUM_THREADS threads"
 
@@ -17,10 +17,10 @@ run_setup()
    ccache -s
 
    # To prevent hitting assertions such as the below:
-   # sb/sb_sched.cpp:1207:schedule_alu: Assertion `!"unscheduled pending instructions"' failed.
+   # sb/sb_sched.cpp:1207:schedule_alu: Assertion '!"unscheduled pending instructions"' failed.
    export R600_DEBUG=nosb
 
-   # If render node, like /dev/dri/renderD128, hasn't been set
+   # If render node, like /dev/dri/renderD128, has not been set
    # or exists use softpipe instead of HW GPU.
    if [[ ! -c $RENDER_DEVICE ]]; then
       export SOFTWARE_ONLY=1