1 files changed, 535 insertions, 0 deletions
diff --git a/mozglue/misc/TimeStamp_windows.cpp b/mozglue/misc/TimeStamp_windows.cpp
new file mode 100644
index 0000000000..e4739ced29
--- /dev/null
+++ b/mozglue/misc/TimeStamp_windows.cpp
@@ -0,0 +1,535 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Implement TimeStamp::Now() with QueryPerformanceCounter() controlled with
+// values of GetTickCount64().
+
+#include "mozilla/DynamicallyLinkedFunctionPtr.h"
+#include "mozilla/MathAlgorithms.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/Uptime.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <intrin.h>
+#include <windows.h>
+
+// To enable logging define to your favorite logging API
+#define LOG(x)
+
+class AutoCriticalSection {
+ public:
+  explicit AutoCriticalSection(LPCRITICAL_SECTION aSection)
+      : mSection(aSection) {
+    ::EnterCriticalSection(mSection);
+  }
+  ~AutoCriticalSection() { ::LeaveCriticalSection(mSection); }
+
+ private:
+  LPCRITICAL_SECTION mSection;
+};
+
+// Estimate of the smallest duration of time we can measure.
+static volatile ULONGLONG sResolution;
+static volatile ULONGLONG sResolutionSigDigs;
+static const double kNsPerSecd = 1000000000.0;
+static const LONGLONG kNsPerMillisec = 1000000;
+
+// ----------------------------------------------------------------------------
+// Global constants
+// ----------------------------------------------------------------------------
+
+// Tolerance to failures settings.
+//
+// What is the interval we want to have failure free.
+// in [ms]
+static const uint32_t kFailureFreeInterval = 5000;
+// How many failures we are willing to tolerate in the interval.
+static const uint32_t kMaxFailuresPerInterval = 4;
+// What is the threshold to treat fluctuations as actual failures.
+// in [ms]
+static const uint32_t kFailureThreshold = 50;
+
+// If we are not able to get the value of GTC time increment, use this value
+// which is the most usual increment.
+static const DWORD kDefaultTimeIncrement = 156001;
+
+// ----------------------------------------------------------------------------
+// Global variables, not changing at runtime
+// ----------------------------------------------------------------------------
+
+// Result of QueryPerformanceFrequency
+// We use default of 1 for the case we can't use QueryPerformanceCounter
+// to make mt/ms conversions work despite that.
+static uint64_t sFrequencyPerSec = 1;
+
+namespace mozilla {
+
+MFBT_API uint64_t GetQueryPerformanceFrequencyPerSec() {
+  return sFrequencyPerSec;
+}
+
+}  // namespace mozilla
+
+// How much we are tolerant to GTC occasional loose of resoltion.
+// This number says how many multiples of the minimal GTC resolution
+// detected on the system are acceptable.  This number is empirical.
+static const LONGLONG kGTCTickLeapTolerance = 4;
+
+// Base tolerance (more: "inability of detection" range) threshold is calculated
+// dynamically, and kept in sGTCResolutionThreshold.
+//
+// Schematically, QPC worked "100%" correctly if ((GTC_now - GTC_epoch) -
+// (QPC_now - QPC_epoch)) was in  [-sGTCResolutionThreshold,
+// sGTCResolutionThreshold] interval every time we'd compared two time stamps.
+// If not, then we check the overflow behind this basic threshold
+// is in kFailureThreshold.  If not, we condider it as a QPC failure.  If too
+// many failures in short time are detected, QPC is considered faulty and
+// disabled.
+//
+// Kept in [mt]
+static LONGLONG sGTCResolutionThreshold;
+
+// If QPC is found faulty for two stamps in this interval, we engage
+// the fault detection algorithm.  For duration larger then this limit
+// we bypass using durations calculated from QPC when jitter is detected,
+// but don't touch the sUseQPC flag.
+//
+// Value is in [ms].
+static const uint32_t kHardFailureLimit = 2000;
+// Conversion to [mt]
+static LONGLONG sHardFailureLimit;
+
+// Conversion of kFailureFreeInterval and kFailureThreshold to [mt]
+static LONGLONG sFailureFreeInterval;
+static LONGLONG sFailureThreshold;
+
+// ----------------------------------------------------------------------------
+// Systemm status flags
+// ----------------------------------------------------------------------------
+
+// Flag for stable TSC that indicates platform where QPC is stable.
+static bool sHasStableTSC = false;
+
+// ----------------------------------------------------------------------------
+// Global state variables, changing at runtime
+// ----------------------------------------------------------------------------
+
+// Initially true, set to false when QPC is found unstable and never
+// returns back to true since that time.
+static bool volatile sUseQPC = true;
+
+// ----------------------------------------------------------------------------
+// Global lock
+// ----------------------------------------------------------------------------
+
+// Thread spin count before entering the full wait state for sTimeStampLock.
+// Inspired by Rob Arnold's work on PRMJ_Now().
+static const DWORD kLockSpinCount = 4096;
+
+// Common mutex (thanks the relative complexity of the logic, this is better
+// then using CMPXCHG8B.)
+// It is protecting the globals bellow.
+static CRITICAL_SECTION sTimeStampLock;
+
+// ----------------------------------------------------------------------------
+// Global lock protected variables
+// ----------------------------------------------------------------------------
+
+// Timestamp in future until QPC must behave correctly.
+// Set to now + kFailureFreeInterval on first QPC failure detection.
+// Set to now + E * kFailureFreeInterval on following errors,
+//   where E is number of errors detected during last kFailureFreeInterval
+//   milliseconds, calculated simply as:
+//   E = (sFaultIntoleranceCheckpoint - now) / kFailureFreeInterval + 1.
+// When E > kMaxFailuresPerInterval -> disable QPC.
+//
+// Kept in [mt]
+static ULONGLONG sFaultIntoleranceCheckpoint = 0;
+
+namespace mozilla {
+
+// Result is in [mt]
+static inline ULONGLONG PerformanceCounter() {
+  LARGE_INTEGER pc;
+  ::QueryPerformanceCounter(&pc);
+
+  // QueryPerformanceCounter may slightly jitter (not be 100% monotonic.)
+  // This is a simple go-backward protection for such a faulty hardware.
+  AutoCriticalSection lock(&sTimeStampLock);
+
+  static decltype(LARGE_INTEGER::QuadPart) last;
+  if (last > pc.QuadPart) {
+    return last * 1000ULL;
+  }
+  last = pc.QuadPart;
+  return pc.QuadPart * 1000ULL;
+}
+
+static void InitThresholds() {
+  DWORD timeAdjustment = 0, timeIncrement = 0;
+  BOOL timeAdjustmentDisabled;
+  GetSystemTimeAdjustment(&timeAdjustment, &timeIncrement,
+                          &timeAdjustmentDisabled);
+
+  LOG(("TimeStamp: timeIncrement=%d [100ns]", timeIncrement));
+
+  if (!timeIncrement) {
+    timeIncrement = kDefaultTimeIncrement;
+  }
+
+  // Ceiling to a millisecond
+  // Example values: 156001, 210000
+  DWORD timeIncrementCeil = timeIncrement;
+  // Don't want to round up if already rounded, values will be: 156000, 209999
+  timeIncrementCeil -= 1;
+  // Convert to ms, values will be: 15, 20
+  timeIncrementCeil /= 10000;
+  // Round up, values will be: 16, 21
+  timeIncrementCeil += 1;
+  // Convert back to 100ns, values will be: 160000, 210000
+  timeIncrementCeil *= 10000;
+
+  // How many milli-ticks has the interval rounded up
+  LONGLONG ticksPerGetTickCountResolutionCeiling =
+      (int64_t(timeIncrementCeil) * sFrequencyPerSec) / 10000LL;
+
+  // GTC may jump by 32 (2*16) ms in two steps, therefor use the ceiling value.
+  sGTCResolutionThreshold =
+      LONGLONG(kGTCTickLeapTolerance * ticksPerGetTickCountResolutionCeiling);
+
+  sHardFailureLimit = ms2mt(kHardFailureLimit);
+  sFailureFreeInterval = ms2mt(kFailureFreeInterval);
+  sFailureThreshold = ms2mt(kFailureThreshold);
+}
+
+static void InitResolution() {
+  // 10 total trials is arbitrary: what we're trying to avoid by
+  // looping is getting unlucky and being interrupted by a context
+  // switch or signal, or being bitten by paging/cache effects
+
+  ULONGLONG minres = ~0ULL;
+  if (sUseQPC) {
+    int loops = 10;
+    do {
+      ULONGLONG start = PerformanceCounter();
+      ULONGLONG end = PerformanceCounter();
+
+      ULONGLONG candidate = (end - start);
+      if (candidate < minres) {
+        minres = candidate;
+      }
+    } while (--loops && minres);
+
+    if (0 == minres) {
+      minres = 1;
+    }
+  } else {
+    // GetTickCount has only ~16ms known resolution
+    minres = ms2mt(16);
+  }
+
+  // Converting minres that is in [mt] to nanosecods, multiplicating
+  // the argument to preserve resolution.
+  ULONGLONG result = mt2ms(minres * kNsPerMillisec);
+  if (0 == result) {
+    result = 1;
+  }
+
+  sResolution = result;
+
+  // find the number of significant digits in mResolution, for the
+  // sake of ToSecondsSigDigits()
+  ULONGLONG sigDigs;
+  for (sigDigs = 1; !(sigDigs == result || 10 * sigDigs > result);
+       sigDigs *= 10)
+    ;
+
+  sResolutionSigDigs = sigDigs;
+}
+
+// ----------------------------------------------------------------------------
+// TimeStampValue implementation
+// ----------------------------------------------------------------------------
+MFBT_API
+TimeStampValue::TimeStampValue(ULONGLONG aGTC, ULONGLONG aQPC, bool aHasQPC,
+                               bool aUsedCanonicalNow)
+    : mGTC(aGTC),
+      mQPC(aQPC),
+      mUsedCanonicalNow(aUsedCanonicalNow),
+      mHasQPC(aHasQPC) {
+  mIsNull = aGTC == 0 && aQPC == 0;
+}
+
+MFBT_API TimeStampValue& TimeStampValue::operator+=(const int64_t aOther) {
+  mGTC += aOther;
+  mQPC += aOther;
+  return *this;
+}
+
+MFBT_API TimeStampValue& TimeStampValue::operator-=(const int64_t aOther) {
+  mGTC -= aOther;
+  mQPC -= aOther;
+  return *this;
+}
+
+// If the duration is less then two seconds, perform check of QPC stability
+// by comparing both GTC and QPC calculated durations of this and aOther.
+MFBT_API uint64_t TimeStampValue::CheckQPC(const TimeStampValue& aOther) const {
+  uint64_t deltaGTC = mGTC - aOther.mGTC;
+
+  if (!mHasQPC || !aOther.mHasQPC) {  // Both not holding QPC
+    return deltaGTC;
+  }
+
+  uint64_t deltaQPC = mQPC - aOther.mQPC;
+
+  if (sHasStableTSC) {  // For stable TSC there is no need to check
+    return deltaQPC;
+  }
+
+  // Check QPC is sane before using it.
+  int64_t diff = DeprecatedAbs(int64_t(deltaQPC) - int64_t(deltaGTC));
+  if (diff <= sGTCResolutionThreshold) {
+    return deltaQPC;
+  }
+
+  // Treat absolutely for calibration purposes
+  int64_t duration = DeprecatedAbs(int64_t(deltaGTC));
+  int64_t overflow = diff - sGTCResolutionThreshold;
+
+  LOG(("TimeStamp: QPC check after %llums with overflow %1.4fms",
+       mt2ms(duration), mt2ms_f(overflow)));
+
+  if (overflow <= sFailureThreshold) {  // We are in the limit, let go.
+    return deltaQPC;
+  }
+
+  // QPC deviates, don't use it, since now this method may only return deltaGTC.
+
+  if (!sUseQPC) {  // QPC already disabled, no need to run the fault tolerance
+                   // algorithm.
+    return deltaGTC;
+  }
+
+  LOG(("TimeStamp: QPC jittered over failure threshold"));
+
+  if (duration < sHardFailureLimit) {
+    // Interval between the two time stamps is very short, consider
+    // QPC as unstable and record a failure.
+    uint64_t now = ms2mt(GetTickCount64());
+
+    AutoCriticalSection lock(&sTimeStampLock);
+
+    if (sFaultIntoleranceCheckpoint && sFaultIntoleranceCheckpoint > now) {
+      // There's already been an error in the last fault intollerant interval.
+      // Time since now to the checkpoint actually holds information on how many
+      // failures there were in the failure free interval we have defined.
+      uint64_t failureCount =
+          (sFaultIntoleranceCheckpoint - now + sFailureFreeInterval - 1) /
+          sFailureFreeInterval;
+      if (failureCount > kMaxFailuresPerInterval) {
+        sUseQPC = false;
+        LOG(("TimeStamp: QPC disabled"));
+      } else {
+        // Move the fault intolerance checkpoint more to the future, prolong it
+        // to reflect the number of detected failures.
+        ++failureCount;
+        sFaultIntoleranceCheckpoint = now + failureCount * sFailureFreeInterval;
+        LOG(("TimeStamp: recording %dth QPC failure", failureCount));
+      }
+    } else {
+      // Setup fault intolerance checkpoint in the future for first detected
+      // error.
+      sFaultIntoleranceCheckpoint = now + sFailureFreeInterval;
+      LOG(("TimeStamp: recording 1st QPC failure"));
+    }
+  }
+
+  return deltaGTC;
+}
+
+MFBT_API uint64_t
+TimeStampValue::operator-(const TimeStampValue& aOther) const {
+  if (IsNull() && aOther.IsNull()) {
+    return uint64_t(0);
+  }
+
+  return CheckQPC(aOther);
+}
+
+// ----------------------------------------------------------------------------
+// TimeDuration and TimeStamp implementation
+// ----------------------------------------------------------------------------
+
+MFBT_API double BaseTimeDurationPlatformUtils::ToSeconds(int64_t aTicks) {
+  // Converting before arithmetic avoids blocked store forward
+  return double(aTicks) / (double(sFrequencyPerSec) * 1000.0);
+}
+
+MFBT_API double BaseTimeDurationPlatformUtils::ToSecondsSigDigits(
+    int64_t aTicks) {
+  // don't report a value < mResolution ...
+  LONGLONG resolution = sResolution;
+  LONGLONG resolutionSigDigs = sResolutionSigDigs;
+  LONGLONG valueSigDigs = resolution * (aTicks / resolution);
+  // and chop off insignificant digits
+  valueSigDigs = resolutionSigDigs * (valueSigDigs / resolutionSigDigs);
+  return double(valueSigDigs) / kNsPerSecd;
+}
+
+MFBT_API int64_t
+BaseTimeDurationPlatformUtils::TicksFromMilliseconds(double aMilliseconds) {
+  double result = ms2mt(aMilliseconds);
+  if (result > double(INT64_MAX)) {
+    return INT64_MAX;
+  } else if (result < double(INT64_MIN)) {
+    return INT64_MIN;
+  }
+
+  return result;
+}
+
+MFBT_API int64_t BaseTimeDurationPlatformUtils::ResolutionInTicks() {
+  return static_cast<int64_t>(sResolution);
+}
+
+static bool HasStableTSC() {
+#if defined(_M_ARM64)
+  // AArch64 defines that its system counter run at a constant rate
+  // regardless of the current clock frequency of the system.  See "The
+  // Generic Timer", section D7, in the ARMARM for ARMv8.
+  return true;
+#else
+  union {
+    int regs[4];
+    struct {
+      int nIds;
+      char cpuString[12];
+    };
+  } cpuInfo;
+
+  __cpuid(cpuInfo.regs, 0);
+  // Only allow Intel or AMD CPUs for now.
+  // The order of the registers is reg[1], reg[3], reg[2].  We just adjust the
+  // string so that we can compare in one go.
+  if (_strnicmp(cpuInfo.cpuString, "GenuntelineI", sizeof(cpuInfo.cpuString)) &&
+      _strnicmp(cpuInfo.cpuString, "AuthcAMDenti", sizeof(cpuInfo.cpuString))) {
+    return false;
+  }
+
+  int regs[4];
+
+  // detect if the Advanced Power Management feature is supported
+  __cpuid(regs, 0x80000000);
+  if ((unsigned int)regs[0] < 0x80000007) {
+    // XXX should we return true here?  If there is no APM there may be
+    // no way how TSC can run out of sync among cores.
+    return false;
+  }
+
+  __cpuid(regs, 0x80000007);
+  // if bit 8 is set than TSC will run at a constant rate
+  // in all ACPI P-states, C-states and T-states
+  return regs[3] & (1 << 8);
+#endif
+}
+
+static bool gInitialized = false;
+
+MFBT_API void TimeStamp::Startup() {
+  if (gInitialized) {
+    return;
+  }
+
+  gInitialized = true;
+
+  // Decide which implementation to use for the high-performance timer.
+
+  InitializeCriticalSectionAndSpinCount(&sTimeStampLock, kLockSpinCount);
+
+  bool forceGTC = false;
+  bool forceQPC = false;
+
+  char* modevar = getenv("MOZ_TIMESTAMP_MODE");
+  if (modevar) {
+    if (!strcmp(modevar, "QPC")) {
+      forceQPC = true;
+    } else if (!strcmp(modevar, "GTC")) {
+      forceGTC = true;
+    }
+  }
+
+  LARGE_INTEGER freq;
+  sUseQPC = !forceGTC && ::QueryPerformanceFrequency(&freq);
+  if (!sUseQPC) {
+    // No Performance Counter.  Fall back to use GetTickCount64.
+    InitResolution();
+
+    LOG(("TimeStamp: using GetTickCount64"));
+    return;
+  }
+
+  sHasStableTSC = forceQPC || HasStableTSC();
+  LOG(("TimeStamp: HasStableTSC=%d", sHasStableTSC));
+
+  sFrequencyPerSec = freq.QuadPart;
+  LOG(("TimeStamp: QPC frequency=%llu", sFrequencyPerSec));
+
+  InitThresholds();
+  InitResolution();
+
+  return;
+}
+
+MFBT_API void TimeStamp::Shutdown() { DeleteCriticalSection(&sTimeStampLock); }
+
+TimeStampValue NowInternal(bool aHighResolution) {
+  // sUseQPC is volatile
+  bool useQPC = (aHighResolution && sUseQPC);
+
+  // Both values are in [mt] units.
+  ULONGLONG QPC = useQPC ? PerformanceCounter() : uint64_t(0);
+  ULONGLONG GTC = ms2mt(GetTickCount64());
+  return TimeStampValue(GTC, QPC, useQPC, false);
+}
+
+MFBT_API TimeStamp TimeStamp::Now(bool aHighResolution) {
+  return TimeStamp::NowFuzzy(NowInternal(aHighResolution));
+}
+
+MFBT_API TimeStamp TimeStamp::NowUnfuzzed(bool aHighResolution) {
+  return TimeStamp(NowInternal(aHighResolution));
+}
+
+// Computes and returns the process uptime in microseconds.
+// Returns 0 if an error was encountered.
+
+MFBT_API uint64_t TimeStamp::ComputeProcessUptime() {
+  FILETIME start, foo, bar, baz;
+  bool success = GetProcessTimes(GetCurrentProcess(), &start, &foo, &bar, &baz);
+  if (!success) {
+    return 0;
+  }
+
+  static const StaticDynamicallyLinkedFunctionPtr<void(WINAPI*)(LPFILETIME)>
+      pGetSystemTimePreciseAsFileTime(L"kernel32.dll",
+                                      "GetSystemTimePreciseAsFileTime");
+
+  FILETIME now;
+  if (pGetSystemTimePreciseAsFileTime) {
+    pGetSystemTimePreciseAsFileTime(&now);
+  } else {
+    GetSystemTimeAsFileTime(&now);
+  }
+
+  ULARGE_INTEGER startUsec = {{start.dwLowDateTime, start.dwHighDateTime}};
+  ULARGE_INTEGER nowUsec = {{now.dwLowDateTime, now.dwHighDateTime}};
+
+  return (nowUsec.QuadPart - startUsec.QuadPart) / 10ULL;
+}
+
+}  // namespace mozilla