From 4e336f549912907ecb0d7a08331471f7cbee216c Mon Sep 17 00:00:00 2001
From: aph <unknown>
Date: Wed, 28 Jul 2010 17:38:21 +0100
Subject: [PATCH] 6888526: Linux getCurrentThreadCpuTime is drastically slower
 than Windows Reviewed-by: dcubed, dholmes

---
 src/os/linux/vm/globals_linux.hpp  | 7 ++++---
 src/share/vm/runtime/arguments.cpp | 6 ++++++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/os/linux/vm/globals_linux.hpp b/src/os/linux/vm/globals_linux.hpp
index 14b22bf7c..75b313737 100644
--- a/src/os/linux/vm/globals_linux.hpp
+++ b/src/os/linux/vm/globals_linux.hpp
@@ -29,9 +29,10 @@
   product(bool, UseOprofile, false,                                 \
         "enable support for Oprofile profiler")                     \
                                                                     \
-  product(bool, UseLinuxPosixThreadCPUClocks, false,                \
-          "enable fast Linux Posix clocks where available")         \
-
+  product(bool, UseLinuxPosixThreadCPUClocks, true,                 \
+          "enable fast Linux Posix clocks where available")
+// NB: The default value of UseLinuxPosixThreadCPUClocks may be
+// overridden in Arguments::parse_each_vm_init_arg.
 
 //
 // Defines Linux-specific default values. The flags are available on all
diff --git a/src/share/vm/runtime/arguments.cpp b/src/share/vm/runtime/arguments.cpp
index 5ba65fba4..486112abc 100644
--- a/src/share/vm/runtime/arguments.cpp
+++ b/src/share/vm/runtime/arguments.cpp
@@ -2593,6 +2593,12 @@ SOLARIS_ONLY(
       FLAG_IS_DEFAULT(UseVMInterruptibleIO)) {
     FLAG_SET_DEFAULT(UseVMInterruptibleIO, true);
   }
+#ifdef LINUX
+ if (JDK_Version::current().compare_major(6) <= 0 &&
+      FLAG_IS_DEFAULT(UseLinuxPosixThreadCPUClocks)) {
+    FLAG_SET_DEFAULT(UseLinuxPosixThreadCPUClocks, false);
+  }
+#endif // LINUX
   return JNI_OK;
 }
 
-- 
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