--- .circleci/config-2_1.yml	2021-10-19 11:08:44.000000000 +0100
+++ .circleci/config-2_1.yml.HIGHRES	2021-10-19 11:26:16.000000000 +0100
@@ -40,8 +40,8 @@
     CASSANDRA_SKIP_SYNC: true
     DTEST_REPO: https://github.com/apache/cassandra-dtest.git
     DTEST_BRANCH: trunk
-    CCM_MAX_HEAP_SIZE: 1024M
-    CCM_HEAP_NEWSIZE: 256M
+    CCM_MAX_HEAP_SIZE: 2048M
+    CCM_HEAP_NEWSIZE: 512M
 
     # The Ant test target to run, for example:
     # REPEATED_UTEST_TARGET: testsome
@@ -100,46 +100,50 @@
 j8_par_executor: &j8_par_executor
   executor:
     name: java8-executor
-    #exec_resource_class: xlarge
-  parallelism: 4
+    exec_resource_class: xlarge
+  parallelism: 100
 
 j8_small_par_executor: &j8_small_par_executor
   executor:
     name: java8-executor
-    #exec_resource_class: xlarge
-  parallelism: 1
+    exec_resource_class: xlarge
+  parallelism: 2
 
 j8_medium_par_executor: &j8_medium_par_executor
   executor:
     name: java8-executor
-    #exec_resource_class: xlarge
-  parallelism: 1
+    exec_resource_class: xlarge
+  parallelism: 2
 
 j8_seq_executor: &j8_seq_executor
   executor:
     name: java8-executor
-    #exec_resource_class: xlarge
+    exec_resource_class: xlarge
   parallelism: 1 # sequential, single container tests: no parallelism benefits
 
 j8_repeated_utest_executor: &j8_repeated_utest_executor
   executor:
     name: java8-executor
-  parallelism: 4
+    exec_resource_class: xlarge
+  parallelism: 100
 
 j8_repeated_dtest_executor: &j8_repeated_dtest_executor
   executor:
     name: java8-executor
-  parallelism: 4
+    exec_resource_class: xlarge
+  parallelism: 100
 
 j8_repeated_upgrade_dtest_executor: &j8_repeated_upgrade_dtest_executor
   executor:
     name: java8-executor
-  parallelism: 4
+    exec_resource_class: xlarge
+  parallelism: 100
 
 j8_repeated_jvm_upgrade_dtest_executor: &j8_repeated_jvm_upgrade_dtest_executor
   executor:
     name: java8-executor
-  parallelism: 4
+    exec_resource_class: xlarge
+  parallelism: 100
 
 with_dtests_jobs: &with_dtest_jobs
   jobs: