Merge pull request #705 from yuslepukhin/rate_limiter_fix

Make WinEnv::NowMicros return system time

include/rocksdb/env.h

@@ -257,6 +257,8 @@ class Env {
 
   // Returns the number of micro-seconds since some fixed point in time. Only
   // useful for computing deltas of time.
+  // However, it is often used as system time such as in GenericRateLimiter
+  // and other places so a port needs to return system time in order to work.
   virtual uint64_t NowMicros() = 0;
 
   // Returns the number of nano-seconds since some fixed point in time. Only

port/win/env_win.cc

@@ -1816,15 +1816,24 @@ class WinEnv : public Env {
   }
 
   virtual uint64_t NowMicros() override {
-    // all std::chrono clocks on windows have the same resolution that is only
-    // On Windows 8 and Windows 2012 Server
-    // GetSystemTimePreciseAsFileTime(&current_time) can be used
+    // all std::chrono clocks on windows proved to return
+    // values that may repeat that is not good enough for some uses.
+    const int64_t c_UnixEpochStartTicks = 116444736000000000i64;
+    const int64_t c_FtToMicroSec = 10;
+
+    // This interface needs to return system time and not
+    // just any microseconds because it is often used as an argument
+    // to TimedWait() on condition variable
+    FILETIME ftSystemTime;
+    GetSystemTimePreciseAsFileTime(&ftSystemTime);
+
     LARGE_INTEGER li;
-    QueryPerformanceCounter(&li);
-    // Convert to nanoseconds first to avoid loss of precision
-    // and divide by frequency
-    li.QuadPart *= std::micro::den;
-    li.QuadPart /= perf_counter_frequency_;
+    li.LowPart = ftSystemTime.dwLowDateTime;
+    li.HighPart = ftSystemTime.dwHighDateTime;
+    // Subtract unix epoch start
+    li.QuadPart -= c_UnixEpochStartTicks;
+    // Convert to microsecs
+    li.QuadPart /= c_FtToMicroSec;
     return li.QuadPart;
   }
 

port/win/port_win.cc

@@ -88,13 +88,16 @@ bool CondVar::TimedWait(uint64_t abs_time_us) {
 
   using namespace std::chrono;
 
+  // MSVC++ library implements wait_until in terms of wait_for so
+  // there is not an absolute wait anyway.
   microseconds usAbsTime(abs_time_us);
+
   microseconds usNow(
       duration_cast<microseconds>(system_clock::now().time_since_epoch()));
   microseconds relTimeUs =
       (usAbsTime > usNow) ? (usAbsTime - usNow) : microseconds::zero();
 
-  std::_Cv_status cvStatus = cv_.wait_for(mu_->getLock(), relTimeUs);
+  std::cv_status cvStatus = cv_.wait_for(mu_->getLock(), relTimeUs);
 
 #ifndef NDEBUG
   mu_->locked_ = true;