Switch to CLOCK_BOOTTIME for HSA system clock.

This is consistent with KFD and has significantly better latency.
KFD is taking this as the definition of the SystemClockCounter.

Change-Id: I4c1b3bc58c738206265c55ebefd41356c013bfe5


[ROCm/ROCR-Runtime commit: 0ee82742a7]

projects/rocr-runtime/runtime/hsa-runtime/core/util/lnx/os_linux.cpp

@@ -515,6 +515,25 @@ void DestroySharedMutex(SharedMutex lock) {
   delete *(pthread_rwlock_t**)&lock;
 }
 
+static uint64_t sys_clock_period_ = 0;
+
+uint64_t ReadSystemClock() {
+  struct timespec ts;
+  clock_gettime(CLOCK_BOOTTIME, &ts);
+  uint64_t time = (uint64_t(ts.tv_sec) * 1000000000 + uint64_t(ts.tv_nsec));
+  if (sys_clock_period_ != 1)
+    return time / sys_clock_period_;
+  else
+    return time;
+}
+
+uint64_t SystemClockFrequency() {
+  struct timespec ts;
+  clock_getres(CLOCK_BOOTTIME, &ts);
+  sys_clock_period_ = (uint64_t(ts.tv_sec) * 1000000000 + uint64_t(ts.tv_nsec));
+  return 1000000000 / sys_clock_period_;
+}
+
 }   //  namespace os
 }   //  namespace rocr
 

projects/rocr-runtime/runtime/hsa-runtime/core/util/os.h

@@ -266,6 +266,14 @@ uint64_t ReadAccurateClock();
 /// seconds.  This frequency does not change at runtime.
 /// @return returns the frequency
 uint64_t AccurateClockFrequency();
+
+/// @brief read the system clock which serves as the HSA system clock
+/// counter in KFD.
+uint64_t ReadSystemClock();
+
+/// @brief read the system clock frequency
+uint64_t SystemClockFrequency();
+
 }   //  namespace os
 }   //  namespace rocr
 

projects/rocr-runtime/runtime/hsa-runtime/core/util/win/os_win.cpp

@@ -270,6 +270,16 @@ void DestroySharedMutex(SharedMutex lock) {
   abort();
 }
 
+uint64_t ReadSystemClock() {
+  assert(false && "Not implemented.");
+  abort();
+}
+
+uint64_t SystemClockFrequency() {
+  assert(false && "Not implemented.");
+  abort();
+}
+
 }   //  namespace os
 }   //  namespace rocr