6667833: Remove CacheTimeMillis

Summary: Remove -XX:+CacheTimeMillis option and associated functionality
Reviewed-by: acorn, never

src/os/linux/vm/os_linux.cpp

@@ -1247,19 +1247,13 @@ jlong os::elapsed_frequency() {
   return (1000 * 1000);
 }
 
-jlong os::timeofday() {
+jlong os::javaTimeMillis() {
   timeval time;
   int status = gettimeofday(&time, NULL);
   assert(status != -1, "linux error");
   return jlong(time.tv_sec) * 1000  +  jlong(time.tv_usec / 1000);
 }
 
-// Must return millis since Jan 1 1970 for JVM_CurrentTimeMillis
-// _use_global_time is only set if CacheTimeMillis is true
-jlong os::javaTimeMillis() {
-  return (_use_global_time ? read_global_time() : timeofday());
-}
-
 #ifndef CLOCK_MONOTONIC
 #define CLOCK_MONOTONIC (1)
 #endif

src/os/solaris/vm/os_solaris.cpp

@@ -1691,19 +1691,14 @@ jlong getTimeMillis() {
   return (jlong)(nanotime / NANOSECS_PER_MILLISECS);
 }
 
-jlong os::timeofday() {
+// Must return millis since Jan 1 1970 for JVM_CurrentTimeMillis
+jlong os::javaTimeMillis() {
   timeval t;
   if (gettimeofday( &t, NULL) == -1)
-    fatal1("timeofday: gettimeofday (%s)", strerror(errno));
+    fatal1("os::javaTimeMillis: gettimeofday (%s)", strerror(errno));
   return jlong(t.tv_sec) * 1000  +  jlong(t.tv_usec) / 1000;
 }
 
-// Must return millis since Jan 1 1970 for JVM_CurrentTimeMillis
-// _use_global_time is only set if CacheTimeMillis is true
-jlong os::javaTimeMillis() {
-  return (_use_global_time ? read_global_time() : timeofday());
-}
-
 jlong os::javaTimeNanos() {
   return (jlong)getTimeNanos();
 }

src/os/windows/vm/os_windows.cpp

@@ -732,20 +732,13 @@ FILETIME java_to_windows_time(jlong l) {
   return result;
 }
 
-jlong os::timeofday() {
-  FILETIME wt;
-  GetSystemTimeAsFileTime(&wt);
-  return windows_to_java_time(wt);
-}
-
-
-// Must return millis since Jan 1 1970 for JVM_CurrentTimeMillis
-// _use_global_time is only set if CacheTimeMillis is true
 jlong os::javaTimeMillis() {
   if (UseFakeTimers) {
     return fake_time++;
   } else {
-    return (_use_global_time ? read_global_time() : timeofday());
+    FILETIME wt;
+    GetSystemTimeAsFileTime(&wt);
+    return windows_to_java_time(wt);
   }
 }
 

src/share/vm/runtime/arguments.cpp

@@ -1255,12 +1255,10 @@ void Arguments::set_bytecode_flags() {
 // Aggressive optimization flags  -XX:+AggressiveOpts
 void Arguments::set_aggressive_opts_flags() {
   if (AggressiveOpts) {
-NOT_WINDOWS(
-    // No measured benefit on Windows
-    if (FLAG_IS_DEFAULT(CacheTimeMillis)) {
-      FLAG_SET_DEFAULT(CacheTimeMillis, true);
-    }
-)
+// Sample flag setting code
+//    if (FLAG_IS_DEFAULT(EliminateZeroing)) {
+//      FLAG_SET_DEFAULT(EliminateZeroing, true);
+//    }
   }
 }
 

src/share/vm/runtime/globals.hpp

@@ -344,12 +344,6 @@ class CommandLineFlags {
   product(bool, ForceTimeHighResolution, false,                             \
           "Using high time resolution(For Win32 only)")                     \
                                                                             \
-  product(bool, CacheTimeMillis, false,                                     \
-          "Cache os::javaTimeMillis with CacheTimeMillisGranularity")       \
-                                                                            \
-  diagnostic(uintx, CacheTimeMillisGranularity, 50,                         \
-          "Granularity for CacheTimeMillis")                                \
-                                                                            \
   develop(bool, TraceItables, false,                                        \
           "Trace initialization and use of itables")                        \
                                                                             \

src/share/vm/runtime/java.cpp

@@ -390,11 +390,6 @@ void before_exit(JavaThread * thread) {
   StatSampler::disengage();
   StatSampler::destroy();
 
-  // shut down the TimeMillisUpdateTask
-  if (CacheTimeMillis) {
-    TimeMillisUpdateTask::disengage();
-  }
-
 #ifndef SERIALGC
   // stop CMS threads
   if (UseConcMarkSweepGC) {

src/share/vm/runtime/os.cpp

@@ -33,9 +33,6 @@ volatile int32_t* os::_mem_serialize_page = NULL;
 uintptr_t         os::_serialize_page_mask = 0;
 long              os::_rand_seed          = 1;
 int               os::_processor_count    = 0;
-volatile jlong    os::_global_time        = 0;
-volatile int      os::_global_time_lock   = 0;
-bool              os::_use_global_time    = false;
 size_t            os::_page_sizes[os::page_sizes_max];
 
 #ifndef PRODUCT
@@ -44,74 +41,6 @@ size_t os::alloc_bytes = 0;         // # of bytes allocated
 int os::num_frees = 0;              // # of calls to free
 #endif
 
-// Atomic read of a jlong is assured by a seqlock; see update_global_time()
-jlong os::read_global_time() {
-#ifdef _LP64
-  return _global_time;
-#else
-  volatile int lock;
-  volatile jlong current_time;
-  int ctr = 0;
-
-  for (;;) {
-    lock = _global_time_lock;
-
-    // spin while locked
-    while ((lock & 0x1) != 0) {
-      ++ctr;
-      if ((ctr & 0xFFF) == 0) {
-        // Guarantee writer progress.  Can't use yield; yield is advisory
-        // and has almost no effect on some platforms.  Don't need a state
-        // transition - the park call will return promptly.
-        assert(Thread::current() != NULL, "TLS not initialized");
-        assert(Thread::current()->_ParkEvent != NULL, "sync not initialized");
-        Thread::current()->_ParkEvent->park(1);
-      }
-      lock = _global_time_lock;
-    }
-
-    OrderAccess::loadload();
-    current_time = _global_time;
-    OrderAccess::loadload();
-
-    // ratify seqlock value
-    if (lock == _global_time_lock) {
-      return current_time;
-    }
-  }
-#endif
-}
-
-//
-// NOTE - Assumes only one writer thread!
-//
-// We use a seqlock to guarantee that jlong _global_time is updated
-// atomically on 32-bit platforms.  A locked value is indicated by
-// the lock variable LSB == 1.  Readers will initially read the lock
-// value, spinning until the LSB == 0.  They then speculatively read
-// the global time value, then re-read the lock value to ensure that
-// it hasn't changed.  If the lock value has changed, the entire read
-// sequence is retried.
-//
-// Writers simply set the LSB = 1 (i.e. increment the variable),
-// update the global time, then release the lock and bump the version
-// number (i.e. increment the variable again.)  In this case we don't
-// even need a CAS since we ensure there's only one writer.
-//
-void os::update_global_time() {
-#ifdef _LP64
-  _global_time = timeofday();
-#else
-  assert((_global_time_lock & 0x1) == 0, "multiple writers?");
-  jlong current_time = timeofday();
-  _global_time_lock++; // lock
-  OrderAccess::storestore();
-  _global_time = current_time;
-  OrderAccess::storestore();
-  _global_time_lock++; // unlock
-#endif
-}
-
 // Fill in buffer with current local time as an ISO-8601 string.
 // E.g., yyyy-mm-ddThh:mm:ss-zzzz.
 // Returns buffer, or NULL if it failed.
@@ -138,7 +67,7 @@ char* os::iso8601_time(char* buffer, size_t buffer_length) {
     return NULL;
   }
   // Get the current time
-  jlong milliseconds_since_19700101 = timeofday();
+  jlong milliseconds_since_19700101 = javaTimeMillis();
   const int milliseconds_per_microsecond = 1000;
   const time_t seconds_since_19700101 =
     milliseconds_since_19700101 / milliseconds_per_microsecond;

src/share/vm/runtime/os.hpp

@@ -66,9 +66,6 @@ class os: AllStatic {
   static address            _polling_page;
   static volatile int32_t * _mem_serialize_page;
   static uintptr_t          _serialize_page_mask;
-  static volatile jlong     _global_time;
-  static volatile int       _global_time_lock;
-  static bool               _use_global_time;
   static size_t             _page_sizes[page_sizes_max];
 
   static void init_page_sizes(size_t default_page_size) {
@@ -88,11 +85,6 @@ class os: AllStatic {
   static bool getenv(const char* name, char* buffer, int len);
   static bool have_special_privileges();
 
-  static jlong  timeofday();
-  static void   enable_global_time()   { _use_global_time = true; }
-  static void   disable_global_time()  { _use_global_time = false; }
-  static jlong  read_global_time();
-  static void   update_global_time();
   static jlong  javaTimeMillis();
   static jlong  javaTimeNanos();
   static void   javaTimeNanos_info(jvmtiTimerInfo *info_ptr);

src/share/vm/runtime/task.cpp

@@ -107,25 +107,3 @@ void PeriodicTask::disenroll() {
     _tasks[index] = _tasks[index+1];
   }
 }
-
-TimeMillisUpdateTask* TimeMillisUpdateTask::_task = NULL;
-
-void TimeMillisUpdateTask::task() {
-  os::update_global_time();
-}
-
-void TimeMillisUpdateTask::engage() {
-  assert(_task == NULL, "init twice?");
-  os::update_global_time(); // initial update
-  os::enable_global_time();
-  _task = new TimeMillisUpdateTask(CacheTimeMillisGranularity);
-  _task->enroll();
-}
-
-void TimeMillisUpdateTask::disengage() {
-  assert(_task != NULL, "uninit twice?");
-  os::disable_global_time();
-  _task->disenroll();
-  delete _task;
-  _task = NULL;
-}

src/share/vm/runtime/task.hpp

@@ -113,13 +113,3 @@ class PeriodicTask: public CHeapObj {
   // The task to perform at each period
   virtual void task() = 0;
 };
-
-class TimeMillisUpdateTask : public PeriodicTask {
- private:
-  static TimeMillisUpdateTask* _task;
- public:
-  TimeMillisUpdateTask(int interval) : PeriodicTask(interval) {}
-  void task();
-  static void engage();
-  static void disengage();
-};

src/share/vm/runtime/thread.cpp

@@ -3066,7 +3066,6 @@ jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
   if (MemProfiling)                   MemProfiler::engage();
   StatSampler::engage();
   if (CheckJNICalls)                  JniPeriodicChecker::engage();
-  if (CacheTimeMillis)                TimeMillisUpdateTask::engage();
 
   BiasedLocking::init();