--- a/hotspot/src/cpu/ppc/vm/globals_ppc.hpp	Tue Nov 08 16:30:36 2016 +0100
+++ b/hotspot/src/cpu/ppc/vm/globals_ppc.hpp	Mon Dec 19 15:48:57 2016 -0800
@@ -42,6 +42,9 @@
 
 #define DEFAULT_STACK_YELLOW_PAGES (2)
 #define DEFAULT_STACK_RED_PAGES (1)
+// Java_java_net_SocketOutputStream_socketWrite0() uses a 64k buffer on the
+// stack if compiled for unix and LP64. To pass stack overflow tests we need
+// 20 shadow pages.
 #define DEFAULT_STACK_SHADOW_PAGES (20 DEBUG_ONLY(+2))
 #define DEFAULT_STACK_RESERVED_PAGES (1)