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/* Copyright (C) 2010 Wildfire Games.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
/*
* Timer implementation using QueryPerformanceCounter
*/
#include "precompiled.h"
#include "lib/sysdep/os/win/whrt/qpc.h"
#include "lib/sysdep/os/win/whrt/counter.h"
#include "lib/sysdep/os_cpu.h"
#include "lib/sysdep/os/win/win.h"
#include "lib/sysdep/os/win/wutil.h" // wutil_argv
#include "lib/sysdep/os/win/whrt/pit.h" // PIT_FREQ
#include "lib/sysdep/os/win/whrt/pmt.h" // PMT_FREQ
class CounterQPC : public ICounter
{
public:
CounterQPC()
: m_frequency(-1)
{
}
virtual const char* Name() const
{
return "QPC";
}
Status Activate()
{
// note: QPC is observed to be universally supported, but the API
// provides for failure, so play it safe.
LARGE_INTEGER qpcFreq, qpcValue;
const BOOL ok1 = QueryPerformanceFrequency(&qpcFreq);
const BOOL ok2 = QueryPerformanceCounter(&qpcValue);
if(!ok1 || !ok2)
WARN_RETURN(ERR::FAIL);
if(!qpcFreq.QuadPart || !qpcValue.QuadPart)
WARN_RETURN(ERR::FAIL);
m_frequency = (i64)qpcFreq.QuadPart;
return INFO::OK;
}
void Shutdown()
{
}
bool IsSafe() const
{
// note: we have separate modules that directly access some of the
// counters potentially used by QPC. disabling the redundant counters
// would be ugly (increased coupling). instead, we'll make sure our
// implementations could (if necessary) coexist with QPC, but it
// shouldn't come to that since only one counter is needed/used.
// the PIT is entirely safe (even if annoyingly slow to read)
if(m_frequency == PIT_FREQ)
return true;
// the PMT is generally safe (see discussion in CounterPmt::IsSafe),
// but older QPC implementations had problems with 24-bit rollover.
// "System clock problem can inflate benchmark scores"
// (http://www.lionbridge.com/bi/cont2000/200012/perfcnt.asp ; no longer
// online, nor findable in Google Cache / archive.org) tells of
// incorrect values every 4.6 seconds (i.e. 24 bits @ 3.57 MHz) unless
// the timer is polled in the meantime. fortunately, this is guaranteed
// by our periodic updates (which come at least that often).
if(m_frequency == PMT_FREQ)
return true;
// the TSC has been known to be buggy (even mentioned in MSDN). it is
// used on MP HAL systems and can be detected by comparing QPF with the
// CPU clock. we consider it unsafe unless the user promises (via
// command line) that it's patched and thus reliable on their system.
bool usesTsc = IsSimilarMagnitude((double)m_frequency, os_cpu_ClockFrequency());
// unconfirmed reports indicate QPC sometimes uses 1/3 of the
// CPU clock frequency, so check that as well.
usesTsc |= IsSimilarMagnitude((double)m_frequency, os_cpu_ClockFrequency()/3);
if(usesTsc)
{
const bool isTscSafe = wutil_HasCommandLineArgument(L"-wQpcTscSafe");
return isTscSafe;
}
// the HPET is reliable and used on Vista. it can't easily be recognized
// since its frequency is variable (the spec says > 10 MHz; the master
// 14.318 MHz oscillator is often used). considering frequencies in
// [10, 100 MHz) to be a HPET would be dangerous because it may actually
// be faster or RDTSC slower. we have to exclude all other cases and
// assume it's a HPET - and thus safe - if we get here.
return true;
}
u64 Counter() const
{
// fairly time-critical here, don't check the return value
// (IsSupported made sure it succeeded initially)
LARGE_INTEGER qpc_value;
(void)QueryPerformanceCounter(&qpc_value);
return qpc_value.QuadPart;
}
size_t CounterBits() const
{
// there are reports of incorrect rollover handling in the PMT
// implementation of QPC (see CounterPMT::IsSafe). however, other
// counters would be used on those systems, so it's irrelevant.
// we'll report the full 64 bits.
return 64;
}
double NominalFrequency() const
{
return (double)m_frequency;
}
double Resolution() const
{
return 1.0 / m_frequency;
}
private:
// used in several places and QPF is a bit slow+cumbersome.
// (i64 allows easier conversion to double)
i64 m_frequency;
};
ICounter* CreateCounterQPC(void* address, size_t size)
{
ENSURE(sizeof(CounterQPC) <= size);
return new(address) CounterQPC();
}
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