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diff src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp @ 671:d0994e5bebce

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6822204: volatile fences should prefer lock:addl to actual mfence instructions Reviewed-by: kvn, phh
author never
date Thu, 26 Mar 2009 14:31:45 -0700
parents a61af66fc99e
children bd02caa94611
line wrap: on
line diff
--- a/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp	Tue Mar 24 15:09:52 2009 -0700
+++ b/src/os_cpu/linux_x86/vm/orderAccess_linux_x86.inline.hpp	Thu Mar 26 14:31:45 2009 -0700
@@ -44,11 +44,12 @@
 
 inline void OrderAccess::fence() {
   if (os::is_MP()) {
+    // always use locked addl since mfence is sometimes expensive
 #ifdef AMD64
-    __asm__ __volatile__ ("mfence":::"memory");
+    __asm__ volatile ("lock; addl $0,0(%%rsp)" : : : "cc", "memory");
 #else
     __asm__ volatile ("lock; addl $0,0(%%esp)" : : : "cc", "memory");
-#endif // AMD64
+#endif
   }
 }