static void
NowCalibrate()
{
FILETIME ft, ftStart;
LARGE_INTEGER liFreq, now;
if (calibration.freq == 0.0) {
if(!QueryPerformanceFrequency(&liFreq)) {
/* High-performance timer is unavailable */
calibration.freq = -1.0;
} else {
calibration.freq = (long double) liFreq.QuadPart;
}
}
if (calibration.freq > 0.0) {
JSInt64 calibrationDelta = 0;
/* By wrapping a timeBegin/EndPeriod pair of calls around this loop,
the loop seems to take much less time (1 ms vs 15ms) on Vista. */
timeBeginPeriod(1);
LowResTime(&ftStart);
do {
LowResTime(&ft);
} while (memcmp(&ftStart,&ft, sizeof(ft)) == 0);
timeEndPeriod(1);
#ifdef WINCE
calibration.granularity = (FILETIME2INT64(ft) -
FILETIME2INT64(ftStart))/10;
#endif
/*
calibrationDelta = (FILETIME2INT64(ft) - FILETIME2INT64(ftStart))/10;
fprintf(stderr, "Calibration delta was %I64d us\n", calibrationDelta);
*/
QueryPerformanceCounter(&now);
calibration.offset = (long double) FILETIME2INT64(ft);
calibration.timer_offset = (long double) now.QuadPart;
/* The windows epoch is around 1600. The unix epoch is around
1970. win2un is the difference (in windows time units which
are 10 times more highres than the JS time unit) */
calibration.offset -= win2un;
calibration.offset *= 0.1;
calibration.last = 0;
calibration.calibrated = JS_TRUE;
}
}
int64_t
PRMJ_Now(void)
{
static int nCalls = 0;
long double lowresTime, highresTimerValue;
FILETIME ft;
LARGE_INTEGER now;
bool calibrated = false;
bool needsCalibration = false;
int64_t returnedTime;
long double cachedOffset = 0.0;
/* For non threadsafe platforms, NowInit is not necessary */
#ifdef JS_THREADSAFE
PR_CallOnce(&calibrationOnce, NowInit);
#endif
do {
if (!calibration.calibrated || needsCalibration) {
MUTEX_LOCK(&calibration.calibration_lock);
MUTEX_LOCK(&calibration.data_lock);
/* Recalibrate only if no one else did before us */
if(calibration.offset == cachedOffset) {
/* Since calibration can take a while, make any other
threads immediately wait */
MUTEX_SETSPINCOUNT(&calibration.data_lock, 0);
NowCalibrate();
calibrated = true;
/* Restore spin count */
MUTEX_SETSPINCOUNT(&calibration.data_lock, DATALOCK_SPINCOUNT);
}
MUTEX_UNLOCK(&calibration.data_lock);
MUTEX_UNLOCK(&calibration.calibration_lock);
}
/* Calculate a low resolution time */
GetSystemTimeAsFileTime(&ft);
lowresTime = 0.1*(long double)(FILETIME2INT64(ft) - win2un);
if (calibration.freq > 0.0) {
long double highresTime, diff;
DWORD timeAdjustment, timeIncrement;
BOOL timeAdjustmentDisabled;
/* Default to 15.625 ms if the syscall fails */
long double skewThreshold = 15625.25;
/* Grab high resolution time */
QueryPerformanceCounter(&now);
highresTimerValue = (long double)now.QuadPart;
MUTEX_LOCK(&calibration.data_lock);
highresTime = calibration.offset + PRMJ_USEC_PER_SEC*
(highresTimerValue-calibration.timer_offset)/calibration.freq;
cachedOffset = calibration.offset;
/* On some dual processor/core systems, we might get an earlier time
so we cache the last time that we returned */
calibration.last = js::Max(calibration.last, int64_t(highresTime));
returnedTime = calibration.last;
MUTEX_UNLOCK(&calibration.data_lock);
/* Rather than assume the NT kernel ticks every 15.6ms, ask it */
if (GetSystemTimeAdjustment(&timeAdjustment,
&timeIncrement,
&timeAdjustmentDisabled)) {
if (timeAdjustmentDisabled) {
/* timeAdjustment is in units of 100ns */
skewThreshold = timeAdjustment/10.0;
} else {
/* timeIncrement is in units of 100ns */
skewThreshold = timeIncrement/10.0;
}
}
/* Check for clock skew */
diff = lowresTime - highresTime;
/* For some reason that I have not determined, the skew can be
up to twice a kernel tick. This does not seem to happen by
itself, but I have only seen it triggered by another program
doing some kind of file I/O. The symptoms are a negative diff
followed by an equally large positive diff. */
if (mozilla::Abs(diff) > 2 * skewThreshold) {
/*fprintf(stderr,"Clock skew detected (diff = %f)!\n", diff);*/
if (calibrated) {
/* If we already calibrated once this instance, and the
clock is still skewed, then either the processor(s) are
wildly changing clockspeed or the system is so busy that
we get switched out for long periods of time. In either
case, it would be infeasible to make use of high
resolution results for anything, so let's resort to old
behavior for this call. It's possible that in the
future, the user will want the high resolution timer, so
we don't disable it entirely. */
returnedTime = int64_t(lowresTime);
needsCalibration = false;
} else {
/* It is possible that when we recalibrate, we will return a
value less than what we have returned before; this is
unavoidable. We cannot tell the different between a
faulty QueryPerformanceCounter implementation and user
changes to the operating system time. Since we must
respect user changes to the operating system time, we
cannot maintain the invariant that Date.now() never
decreases; the old implementation has this behavior as
well. */
needsCalibration = true;
}
} else {
/* No detectable clock skew */
returnedTime = int64_t(highresTime);
needsCalibration = false;
}
} else {
/* No high resolution timer is available, so fall back */
returnedTime = int64_t(lowresTime);
}
} while (needsCalibration);
return returnedTime;
}
JSInt64
PRMJ_Now(void)
{
#ifdef XP_OS2
JSInt64 s, us, ms2us, s2us;
struct timeb b;
#endif
#ifdef XP_WIN
static int nCalls = 0;
long double lowresTime, highresTimerValue;
FILETIME ft;
LARGE_INTEGER now;
JSBool calibrated = JS_FALSE;
JSBool needsCalibration = JS_FALSE;
JSInt64 returnedTime;
long double cachedOffset = 0.0;
#endif
#if defined(XP_UNIX) || defined(XP_BEOS)
struct timeval tv;
JSInt64 s, us, s2us;
#endif /* XP_UNIX */
#ifdef XP_OS2
ftime(&b);
JSLL_UI2L(ms2us, PRMJ_USEC_PER_MSEC);
JSLL_UI2L(s2us, PRMJ_USEC_PER_SEC);
JSLL_UI2L(s, b.time);
JSLL_UI2L(us, b.millitm);
JSLL_MUL(us, us, ms2us);
JSLL_MUL(s, s, s2us);
JSLL_ADD(s, s, us);
return s;
#endif
#ifdef XP_WIN
/* To avoid regressing startup time (where high resolution is likely
not needed), give the old behavior for the first few calls.
This does not appear to be needed on Vista as the timeBegin/timeEndPeriod
calls seem to immediately take effect. */
int thiscall = JS_ATOMIC_INCREMENT(&nCalls);
/* 10 seems to be the number of calls to load with a blank homepage */
if (thiscall <= 10) {
GetSystemTimeAsFileTime(&ft);
return (FILETIME2INT64(ft)-win2un)/10L;
}
/* For non threadsafe platforms, NowInit is not necessary */
#ifdef JS_THREADSAFE
PR_CallOnce(&calibrationOnce, NowInit);
#endif
do {
if (!calibration.calibrated || needsCalibration) {
MUTEX_LOCK(&calibration.calibration_lock);
MUTEX_LOCK(&calibration.data_lock);
/* Recalibrate only if no one else did before us */
if(calibration.offset == cachedOffset) {
/* Since calibration can take a while, make any other
threads immediately wait */
MUTEX_SETSPINCOUNT(&calibration.data_lock, 0);
NowCalibrate();
calibrated = JS_TRUE;
/* Restore spin count */
MUTEX_SETSPINCOUNT(&calibration.data_lock, DATALOCK_SPINCOUNT);
}
MUTEX_UNLOCK(&calibration.data_lock);
MUTEX_UNLOCK(&calibration.calibration_lock);
}
/* Calculate a low resolution time */
GetSystemTimeAsFileTime(&ft);
lowresTime = 0.1*(long double)(FILETIME2INT64(ft) - win2un);
if (calibration.freq > 0.0) {
long double highresTime, diff;
DWORD timeAdjustment, timeIncrement;
BOOL timeAdjustmentDisabled;
/* Default to 15.625 ms if the syscall fails */
long double skewThreshold = 15625.25;
/* Grab high resolution time */
QueryPerformanceCounter(&now);
highresTimerValue = (long double)now.QuadPart;
MUTEX_LOCK(&calibration.data_lock);
highresTime = calibration.offset + PRMJ_USEC_PER_SEC*
(highresTimerValue-calibration.timer_offset)/calibration.freq;
cachedOffset = calibration.offset;
/* On some dual processor/core systems, we might get an earlier time
so we cache the last time that we returned */
calibration.last = max(calibration.last,(JSInt64)highresTime);
returnedTime = calibration.last;
MUTEX_UNLOCK(&calibration.data_lock);
/* Rather than assume the NT kernel ticks every 15.6ms, ask it */
if (GetSystemTimeAdjustment(&timeAdjustment,
&timeIncrement,
&timeAdjustmentDisabled)) {
if (timeAdjustmentDisabled) {
/* timeAdjustment is in units of 100ns */
skewThreshold = timeAdjustment/10.0;
} else {
/* timeIncrement is in units of 100ns */
skewThreshold = timeIncrement/10.0;
}
}
/* Check for clock skew */
diff = lowresTime - highresTime;
/* For some reason that I have not determined, the skew can be
up to twice a kernel tick. This does not seem to happen by
itself, but I have only seen it triggered by another program
doing some kind of file I/O. The symptoms are a negative diff
followed by an equally large positive diff. */
if (fabs(diff) > 2*skewThreshold) {
/*fprintf(stderr,"Clock skew detected (diff = %f)!\n", diff);*/
if (calibrated) {
/* If we already calibrated once this instance, and the
clock is still skewed, then either the processor(s) are
wildly changing clockspeed or the system is so busy that
we get switched out for long periods of time. In either
case, it would be infeasible to make use of high
resolution results for anything, so let's resort to old
behavior for this call. It's possible that in the
future, the user will want the high resolution timer, so
we don't disable it entirely. */
returnedTime = (JSInt64)lowresTime;
needsCalibration = JS_FALSE;
} else {
/* It is possible that when we recalibrate, we will return a
value less than what we have returned before; this is
unavoidable. We cannot tell the different between a
faulty QueryPerformanceCounter implementation and user
changes to the operating system time. Since we must
respect user changes to the operating system time, we
cannot maintain the invariant that Date.now() never
decreases; the old implementation has this behavior as
well. */
needsCalibration = JS_TRUE;
}
} else {
/* No detectable clock skew */
returnedTime = (JSInt64)highresTime;
needsCalibration = JS_FALSE;
}
} else {
/* No high resolution timer is available, so fall back */
returnedTime = (JSInt64)lowresTime;
}
} while (needsCalibration);
return returnedTime;
#endif
#if defined(XP_UNIX) || defined(XP_BEOS)
#ifdef _SVID_GETTOD /* Defined only on Solaris, see Solaris <sys/types.h> */
gettimeofday(&tv);
#else
gettimeofday(&tv, 0);
#endif /* _SVID_GETTOD */
JSLL_UI2L(s2us, PRMJ_USEC_PER_SEC);
JSLL_UI2L(s, tv.tv_sec);
JSLL_UI2L(us, tv.tv_usec);
JSLL_MUL(s, s, s2us);
JSLL_ADD(s, s, us);
return s;
#endif /* XP_UNIX */
}
