1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/xpcom/ds/TimeStamp_darwin.cpp Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,195 @@
1.4 +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim:set ts=2 sw=2 sts=2 et cindent: */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +//
1.11 +// Implement TimeStamp::Now() with mach_absolute_time
1.12 +//
1.13 +// The "tick" unit for mach_absolute_time is defined using mach_timebase_info() which
1.14 +// gives a conversion ratio to nanoseconds. For more information see Apple's QA1398.
1.15 +//
1.16 +// This code is inspired by Chromium's time_mac.cc. The biggest
1.17 +// differences are that we explicitly initialize using
1.18 +// TimeStamp::Initialize() instead of lazily in Now() and that
1.19 +// we store the time value in ticks and convert when needed instead
1.20 +// of storing the time value in nanoseconds.
1.21 +
1.22 +#include <mach/mach_time.h>
1.23 +#include <sys/time.h>
1.24 +#include <sys/sysctl.h>
1.25 +#include <time.h>
1.26 +#include <unistd.h>
1.27 +
1.28 +#include "mozilla/TimeStamp.h"
1.29 +#include "nsDebug.h"
1.30 +
1.31 +// Estimate of the smallest duration of time we can measure.
1.32 +static uint64_t sResolution;
1.33 +static uint64_t sResolutionSigDigs;
1.34 +
1.35 +static const uint64_t kNsPerMs = 1000000;
1.36 +static const uint64_t kUsPerSec = 1000000;
1.37 +static const double kNsPerMsd = 1000000.0;
1.38 +static const double kNsPerSecd = 1000000000.0;
1.39 +
1.40 +static bool gInitialized = false;
1.41 +static double sNsPerTick;
1.42 +
1.43 +static uint64_t
1.44 +ClockTime()
1.45 +{
1.46 + // mach_absolute_time is it when it comes to ticks on the Mac. Other calls
1.47 + // with less precision (such as TickCount) just call through to
1.48 + // mach_absolute_time.
1.49 + //
1.50 + // At the time of writing mach_absolute_time returns the number of nanoseconds
1.51 + // since boot. This won't overflow 64bits for 500+ years so we aren't going
1.52 + // to worry about that possiblity
1.53 + return mach_absolute_time();
1.54 +}
1.55 +
1.56 +static uint64_t
1.57 +ClockResolutionNs()
1.58 +{
1.59 + uint64_t start = ClockTime();
1.60 + uint64_t end = ClockTime();
1.61 + uint64_t minres = (end - start);
1.62 +
1.63 + // 10 total trials is arbitrary: what we're trying to avoid by
1.64 + // looping is getting unlucky and being interrupted by a context
1.65 + // switch or signal, or being bitten by paging/cache effects
1.66 + for (int i = 0; i < 9; ++i) {
1.67 + start = ClockTime();
1.68 + end = ClockTime();
1.69 +
1.70 + uint64_t candidate = (start - end);
1.71 + if (candidate < minres)
1.72 + minres = candidate;
1.73 + }
1.74 +
1.75 + if (0 == minres) {
1.76 + // measurable resolution is either incredibly low, ~1ns, or very
1.77 + // high. fall back on NSPR's resolution assumption
1.78 + minres = 1 * kNsPerMs;
1.79 + }
1.80 +
1.81 + return minres;
1.82 +}
1.83 +
1.84 +namespace mozilla {
1.85 +
1.86 +double
1.87 +TimeDuration::ToSeconds() const
1.88 +{
1.89 + NS_ABORT_IF_FALSE(gInitialized, "calling TimeDuration too early");
1.90 + return (mValue * sNsPerTick) / kNsPerSecd;
1.91 +}
1.92 +
1.93 +double
1.94 +TimeDuration::ToSecondsSigDigits() const
1.95 +{
1.96 + NS_ABORT_IF_FALSE(gInitialized, "calling TimeDuration too early");
1.97 + // don't report a value < mResolution ...
1.98 + int64_t valueSigDigs = sResolution * (mValue / sResolution);
1.99 + // and chop off insignificant digits
1.100 + valueSigDigs = sResolutionSigDigs * (valueSigDigs / sResolutionSigDigs);
1.101 + return (valueSigDigs * sNsPerTick) / kNsPerSecd;
1.102 +}
1.103 +
1.104 +TimeDuration
1.105 +TimeDuration::FromMilliseconds(double aMilliseconds)
1.106 +{
1.107 + NS_ABORT_IF_FALSE(gInitialized, "calling TimeDuration too early");
1.108 + return TimeDuration::FromTicks(int64_t((aMilliseconds * kNsPerMsd) / sNsPerTick));
1.109 +}
1.110 +
1.111 +TimeDuration
1.112 +TimeDuration::Resolution()
1.113 +{
1.114 + NS_ABORT_IF_FALSE(gInitialized, "calling TimeDuration too early");
1.115 + return TimeDuration::FromTicks(int64_t(sResolution));
1.116 +}
1.117 +
1.118 +nsresult
1.119 +TimeStamp::Startup()
1.120 +{
1.121 + if (gInitialized)
1.122 + return NS_OK;
1.123 +
1.124 + mach_timebase_info_data_t timebaseInfo;
1.125 + // Apple's QA1398 suggests that the output from mach_timebase_info
1.126 + // will not change while a program is running, so it should be safe
1.127 + // to cache the result.
1.128 + kern_return_t kr = mach_timebase_info(&timebaseInfo);
1.129 + if (kr != KERN_SUCCESS)
1.130 + NS_RUNTIMEABORT("mach_timebase_info failed");
1.131 +
1.132 + sNsPerTick = double(timebaseInfo.numer) / timebaseInfo.denom;
1.133 +
1.134 + sResolution = ClockResolutionNs();
1.135 +
1.136 + // find the number of significant digits in sResolution, for the
1.137 + // sake of ToSecondsSigDigits()
1.138 + for (sResolutionSigDigs = 1;
1.139 + !(sResolutionSigDigs == sResolution
1.140 + || 10*sResolutionSigDigs > sResolution);
1.141 + sResolutionSigDigs *= 10);
1.142 +
1.143 + gInitialized = true;
1.144 +
1.145 + return NS_OK;
1.146 +}
1.147 +
1.148 +void
1.149 +TimeStamp::Shutdown()
1.150 +{
1.151 +}
1.152 +
1.153 +TimeStamp
1.154 +TimeStamp::Now(bool aHighResolution)
1.155 +{
1.156 + return TimeStamp(ClockTime());
1.157 +}
1.158 +
1.159 +// Computes and returns the process uptime in microseconds.
1.160 +// Returns 0 if an error was encountered.
1.161 +
1.162 +uint64_t
1.163 +TimeStamp::ComputeProcessUptime()
1.164 +{
1.165 + struct timeval tv;
1.166 + int rv = gettimeofday(&tv, nullptr);
1.167 +
1.168 + if (rv == -1) {
1.169 + return 0;
1.170 + }
1.171 +
1.172 + int mib[] = {
1.173 + CTL_KERN,
1.174 + KERN_PROC,
1.175 + KERN_PROC_PID,
1.176 + getpid(),
1.177 + };
1.178 + u_int mibLen = sizeof(mib) / sizeof(mib[0]);
1.179 +
1.180 + struct kinfo_proc proc;
1.181 + size_t bufferSize = sizeof(proc);
1.182 + rv = sysctl(mib, mibLen, &proc, &bufferSize, nullptr, 0);
1.183 +
1.184 + if (rv == -1)
1.185 + return 0;
1.186 +
1.187 + uint64_t startTime =
1.188 + ((uint64_t)proc.kp_proc.p_un.__p_starttime.tv_sec * kUsPerSec) +
1.189 + proc.kp_proc.p_un.__p_starttime.tv_usec;
1.190 + uint64_t now = (tv.tv_sec * kUsPerSec) + tv.tv_usec;
1.191 +
1.192 + if (startTime > now)
1.193 + return 0;
1.194 +
1.195 + return now - startTime;
1.196 +}
1.197 +
1.198 +} // namespace mozilla
