michael@0: /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim:set ts=2 sw=2 sts=2 et cindent: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: //
michael@0: // Implement TimeStamp::Now() with mach_absolute_time
michael@0: //
michael@0: // The "tick" unit for mach_absolute_time is defined using mach_timebase_info() which
michael@0: // gives a conversion ratio to nanoseconds. For more information see Apple's QA1398.
michael@0: //
michael@0: // This code is inspired by Chromium's time_mac.cc. The biggest
michael@0: // differences are that we explicitly initialize using
michael@0: // TimeStamp::Initialize() instead of lazily in Now() and that
michael@0: // we store the time value in ticks and convert when needed instead
michael@0: // of storing the time value in nanoseconds.
michael@0: 
michael@0: #include <mach/mach_time.h>
michael@0: #include <sys/time.h>
michael@0: #include <sys/sysctl.h>
michael@0: #include <time.h>
michael@0: #include <unistd.h>
michael@0: 
michael@0: #include "mozilla/TimeStamp.h"
michael@0: #include "nsDebug.h"
michael@0: 
michael@0: // Estimate of the smallest duration of time we can measure.
michael@0: static uint64_t sResolution;
michael@0: static uint64_t sResolutionSigDigs;
michael@0: 
michael@0: static const uint64_t kNsPerMs   =    1000000;
michael@0: static const uint64_t kUsPerSec  =    1000000;
michael@0: static const double kNsPerMsd    =    1000000.0;
michael@0: static const double kNsPerSecd   = 1000000000.0;
michael@0: 
michael@0: static bool gInitialized = false;
michael@0: static double sNsPerTick;
michael@0: 
michael@0: static uint64_t
michael@0: ClockTime()
michael@0: {
michael@0:   // mach_absolute_time is it when it comes to ticks on the Mac.  Other calls
michael@0:   // with less precision (such as TickCount) just call through to
michael@0:   // mach_absolute_time.
michael@0:   //
michael@0:   // At the time of writing mach_absolute_time returns the number of nanoseconds
michael@0:   // since boot. This won't overflow 64bits for 500+ years so we aren't going
michael@0:   // to worry about that possiblity
michael@0:   return mach_absolute_time();
michael@0: }
michael@0: 
michael@0: static uint64_t
michael@0: ClockResolutionNs()
michael@0: {
michael@0:   uint64_t start = ClockTime();
michael@0:   uint64_t end = ClockTime();
michael@0:   uint64_t minres = (end - start);
michael@0: 
michael@0:   // 10 total trials is arbitrary: what we're trying to avoid by
michael@0:   // looping is getting unlucky and being interrupted by a context
michael@0:   // switch or signal, or being bitten by paging/cache effects
michael@0:   for (int i = 0; i < 9; ++i) {
michael@0:     start = ClockTime();
michael@0:     end = ClockTime();
michael@0: 
michael@0:     uint64_t candidate = (start - end);
michael@0:     if (candidate < minres)
michael@0:       minres = candidate;
michael@0:   }
michael@0: 
michael@0:   if (0 == minres) {
michael@0:     // measurable resolution is either incredibly low, ~1ns, or very
michael@0:     // high.  fall back on NSPR's resolution assumption
michael@0:     minres = 1 * kNsPerMs;
michael@0:   }
michael@0: 
michael@0:   return minres;
michael@0: }
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: double
michael@0: TimeDuration::ToSeconds() const
michael@0: {
michael@0:   NS_ABORT_IF_FALSE(gInitialized, "calling TimeDuration too early");
michael@0:   return (mValue * sNsPerTick) / kNsPerSecd;
michael@0: }
michael@0: 
michael@0: double
michael@0: TimeDuration::ToSecondsSigDigits() const
michael@0: {
michael@0:   NS_ABORT_IF_FALSE(gInitialized, "calling TimeDuration too early");
michael@0:   // don't report a value < mResolution ...
michael@0:   int64_t valueSigDigs = sResolution * (mValue / sResolution);
michael@0:   // and chop off insignificant digits
michael@0:   valueSigDigs = sResolutionSigDigs * (valueSigDigs / sResolutionSigDigs);
michael@0:   return (valueSigDigs * sNsPerTick) / kNsPerSecd;
michael@0: }
michael@0: 
michael@0: TimeDuration
michael@0: TimeDuration::FromMilliseconds(double aMilliseconds)
michael@0: {
michael@0:   NS_ABORT_IF_FALSE(gInitialized, "calling TimeDuration too early");
michael@0:   return TimeDuration::FromTicks(int64_t((aMilliseconds * kNsPerMsd) / sNsPerTick));
michael@0: }
michael@0: 
michael@0: TimeDuration
michael@0: TimeDuration::Resolution()
michael@0: {
michael@0:   NS_ABORT_IF_FALSE(gInitialized, "calling TimeDuration too early");
michael@0:   return TimeDuration::FromTicks(int64_t(sResolution));
michael@0: }
michael@0: 
michael@0: nsresult
michael@0: TimeStamp::Startup()
michael@0: {
michael@0:   if (gInitialized)
michael@0:     return NS_OK;
michael@0: 
michael@0:   mach_timebase_info_data_t timebaseInfo;
michael@0:   // Apple's QA1398 suggests that the output from mach_timebase_info
michael@0:   // will not change while a program is running, so it should be safe
michael@0:   // to cache the result.
michael@0:   kern_return_t kr = mach_timebase_info(&timebaseInfo);
michael@0:   if (kr != KERN_SUCCESS)
michael@0:     NS_RUNTIMEABORT("mach_timebase_info failed");
michael@0: 
michael@0:   sNsPerTick = double(timebaseInfo.numer) / timebaseInfo.denom;
michael@0: 
michael@0:   sResolution = ClockResolutionNs();
michael@0: 
michael@0:   // find the number of significant digits in sResolution, for the
michael@0:   // sake of ToSecondsSigDigits()
michael@0:   for (sResolutionSigDigs = 1;
michael@0:        !(sResolutionSigDigs == sResolution
michael@0:          || 10*sResolutionSigDigs > sResolution);
michael@0:        sResolutionSigDigs *= 10);
michael@0: 
michael@0:   gInitialized = true;
michael@0: 
michael@0:   return NS_OK;
michael@0: }
michael@0: 
michael@0: void
michael@0: TimeStamp::Shutdown()
michael@0: {
michael@0: }
michael@0: 
michael@0: TimeStamp
michael@0: TimeStamp::Now(bool aHighResolution)
michael@0: {
michael@0:   return TimeStamp(ClockTime());
michael@0: }
michael@0: 
michael@0: // Computes and returns the process uptime in microseconds.
michael@0: // Returns 0 if an error was encountered.
michael@0: 
michael@0: uint64_t
michael@0: TimeStamp::ComputeProcessUptime()
michael@0: {
michael@0:   struct timeval tv;
michael@0:   int rv = gettimeofday(&tv, nullptr);
michael@0: 
michael@0:   if (rv == -1) {
michael@0:     return 0;
michael@0:   }
michael@0: 
michael@0:   int mib[] = {
michael@0:     CTL_KERN,
michael@0:     KERN_PROC,
michael@0:     KERN_PROC_PID,
michael@0:     getpid(),
michael@0:   };
michael@0:   u_int mibLen = sizeof(mib) / sizeof(mib[0]);
michael@0: 
michael@0:   struct kinfo_proc proc;
michael@0:   size_t bufferSize = sizeof(proc);
michael@0:   rv = sysctl(mib, mibLen, &proc, &bufferSize, nullptr, 0);
michael@0: 
michael@0:   if (rv == -1)
michael@0:     return 0;
michael@0: 
michael@0:   uint64_t startTime =
michael@0:     ((uint64_t)proc.kp_proc.p_un.__p_starttime.tv_sec * kUsPerSec) +
michael@0:     proc.kp_proc.p_un.__p_starttime.tv_usec;
michael@0:   uint64_t now = (tv.tv_sec * kUsPerSec) + tv.tv_usec;
michael@0: 
michael@0:   if (startTime > now)
michael@0:     return 0;
michael@0: 
michael@0:   return now - startTime;
michael@0: }
michael@0: 
michael@0: } // namespace mozilla