/* -*- 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 mach_absolute_time // // The "tick" unit for mach_absolute_time is defined using mach_timebase_info() which // gives a conversion ratio to nanoseconds. For more information see Apple's QA1398. // // This code is inspired by Chromium's time_mac.cc. The biggest // differences are that we explicitly initialize using // TimeStamp::Initialize() instead of lazily in Now() and that // we store the time value in ticks and convert when needed instead // of storing the time value in nanoseconds. #include <mach/mach_time.h> #include <sys/time.h> #include <sys/sysctl.h> #include <time.h> #include <unistd.h> #include "mozilla/TimeStamp.h" // Estimate of the smallest duration of time we can measure. static uint64_t sResolution; static uint64_t sResolutionSigDigs; static const uint64_t kNsPerMs = 1000000; static const uint64_t kUsPerSec = 1000000; static const double kNsPerMsd = 1000000.0; static const double kNsPerSecd = 1000000000.0; static bool gInitialized = false; static double sNsPerTick; static uint64_t ClockTime() { // mach_absolute_time is it when it comes to ticks on the Mac. Other calls // with less precision (such as TickCount) just call through to // mach_absolute_time. // // At the time of writing mach_absolute_time returns the number of nanoseconds // since boot. This won't overflow 64bits for 500+ years so we aren't going // to worry about that possiblity return mach_absolute_time(); } static uint64_t ClockResolutionNs() { uint64_t start = ClockTime(); uint64_t end = ClockTime(); uint64_t minres = (end - start); // 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 for (int i = 0; i < 9; ++i) { start = ClockTime(); end = ClockTime(); uint64_t candidate = (start - end); if (candidate < minres) { minres = candidate; } } if (0 == minres) { // measurable resolution is either incredibly low, ~1ns, or very // high. fall back on NSPR's resolution assumption minres = 1 * kNsPerMs; } return minres; } namespace mozilla { double BaseTimeDurationPlatformUtils::ToSeconds(int64_t aTicks) { MOZ_ASSERT(gInitialized, "calling TimeDuration too early"); return (aTicks * sNsPerTick) / kNsPerSecd; } double BaseTimeDurationPlatformUtils::ToSecondsSigDigits(int64_t aTicks) { MOZ_ASSERT(gInitialized, "calling TimeDuration too early"); // don't report a value < mResolution ... int64_t valueSigDigs = sResolution * (aTicks / sResolution); // and chop off insignificant digits valueSigDigs = sResolutionSigDigs * (valueSigDigs / sResolutionSigDigs); return (valueSigDigs * sNsPerTick) / kNsPerSecd; } int64_t BaseTimeDurationPlatformUtils::TicksFromMilliseconds(double aMilliseconds) { MOZ_ASSERT(gInitialized, "calling TimeDuration too early"); double result = (aMilliseconds * kNsPerMsd) / sNsPerTick; if (result > INT64_MAX) { return INT64_MAX; } else if (result < INT64_MIN) { return INT64_MIN; } return result; } int64_t BaseTimeDurationPlatformUtils::ResolutionInTicks() { MOZ_ASSERT(gInitialized, "calling TimeDuration too early"); return static_cast<int64_t>(sResolution); } void TimeStamp::Startup() { if (gInitialized) { return; } mach_timebase_info_data_t timebaseInfo; // Apple's QA1398 suggests that the output from mach_timebase_info // will not change while a program is running, so it should be safe // to cache the result. kern_return_t kr = mach_timebase_info(&timebaseInfo); if (kr != KERN_SUCCESS) { MOZ_RELEASE_ASSERT(false, "mach_timebase_info failed"); } sNsPerTick = double(timebaseInfo.numer) / timebaseInfo.denom; sResolution = ClockResolutionNs(); // find the number of significant digits in sResolution, for the // sake of ToSecondsSigDigits() for (sResolutionSigDigs = 1; !(sResolutionSigDigs == sResolution || 10 * sResolutionSigDigs > sResolution); sResolutionSigDigs *= 10); gInitialized = true; return; } void TimeStamp::Shutdown() { } TimeStamp TimeStamp::Now(bool aHighResolution) { return TimeStamp(ClockTime()); } // Computes and returns the process uptime in microseconds. // Returns 0 if an error was encountered. uint64_t TimeStamp::ComputeProcessUptime() { struct timeval tv; int rv = gettimeofday(&tv, nullptr); if (rv == -1) { return 0; } int mib[] = { CTL_KERN, KERN_PROC, KERN_PROC_PID, getpid(), }; u_int mibLen = sizeof(mib) / sizeof(mib[0]); struct kinfo_proc proc; size_t bufferSize = sizeof(proc); rv = sysctl(mib, mibLen, &proc, &bufferSize, nullptr, 0); if (rv == -1) { return 0; } uint64_t startTime = ((uint64_t)proc.kp_proc.p_un.__p_starttime.tv_sec * kUsPerSec) + proc.kp_proc.p_un.__p_starttime.tv_usec; uint64_t now = (tv.tv_sec * kUsPerSec) + tv.tv_usec; if (startTime > now) { return 0; } return now - startTime; } } // namespace mozilla