Merge pull request #20006 from eclipse-openj9/revert-19919-master

Revert "Treat single CPU as if -Xgc:noConcurrentMark were set"

Author: zl-wang

runtime/gc_modron_startup/mminit.cpp

@@ -2842,12 +2842,9 @@ configurateGCWithPolicyAndOptionsStandard(MM_EnvironmentBase *env)
 MM_Configuration *
 configurateGCWithPolicyAndOptions(OMR_VM* omrVM)
 {
-	J9JavaVM *vm = (J9JavaVM*) omrVM->_language_vm;
-	PORT_ACCESS_FROM_JAVAVM(vm);
 	MM_Configuration *result = NULL;
 	MM_GCExtensions *extensions = MM_GCExtensions::getExtensions(omrVM);
 	MM_EnvironmentBase env(omrVM);
-	bool ccMark = false;
 
 	switch(extensions->configurationOptions._gcPolicy) {
 	case gc_policy_optthruput:
@@ -2869,9 +2866,8 @@ configurateGCWithPolicyAndOptions(OMR_VM* omrVM)
 	case gc_policy_gencon:
 		extensions->gcModeString = "-Xgcpolicy:gencon";
 		omrVM->gcPolicy = J9_GC_POLICY_GENCON;
-		ccMark = (1 != j9sysinfo_get_number_CPUs_by_type(J9PORT_CPU_TARGET));
 		/* scavenge, concurrentMark, noConcurrentSweep, loa */
-		setDefaultConfigOptions(extensions, true, ccMark, false, true);
+		setDefaultConfigOptions(extensions, true, true, false, true);
 		result = configurateGCWithPolicyAndOptionsStandard(&env);
 		break;