--- a/hotspot/src/cpu/sparc/vm/vm_version_sparc.cpp	Thu Sep 20 16:49:17 2012 +0200
+++ b/hotspot/src/cpu/sparc/vm/vm_version_sparc.cpp	Mon Sep 24 11:07:03 2012 -0700
@@ -339,7 +339,11 @@
 
 unsigned int VM_Version::calc_parallel_worker_threads() {
   unsigned int result;
-  if (is_niagara_plus()) {
+  if (is_M_series()) {
+    // for now, use same gc thread calculation for M-series as for niagara-plus
+    // in future, we may want to tweak parameters for nof_parallel_worker_thread
+    result = nof_parallel_worker_threads(5, 16, 8);
+  } else if (is_niagara_plus()) {
     result = nof_parallel_worker_threads(5, 16, 8);
   } else {
     result = nof_parallel_worker_threads(5, 8, 8);

--- a/hotspot/src/cpu/sparc/vm/vm_version_sparc.hpp	Thu Sep 20 16:49:17 2012 +0200
+++ b/hotspot/src/cpu/sparc/vm/vm_version_sparc.hpp	Mon Sep 24 11:07:03 2012 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -124,6 +124,8 @@
   // Returns true if the platform is in the niagara line (T series)
   // and newer than the niagara1.
   static bool is_niagara_plus()         { return is_T_family(_features) && !is_T1_model(_features); }
+
+  static bool is_M_series()             { return is_M_family(_features); }
   static bool is_T4()                   { return is_T_family(_features) && has_cbcond(); }
 
   // Fujitsu SPARC64