Added: Function and tool to check system timer sanity across cpu cores

This commit is contained in:
kaetemi 2012-07-27 21:20:07 +02:00
parent 09c3e0880d
commit 96d8d45c1d
5 changed files with 198 additions and 0 deletions

View file

@ -48,6 +48,19 @@ typedef sint64 TTicks;
class CTime
{
public:
struct CTimerInfo
{
/// Returns if there is a high precision timer that can be used.
bool IsHighPrecisionAvailable;
/// If a CPU specific timer is used and the values are not consistent accross threads.
bool RequiresSingleCore;
/// The resolution of the high resolution timer.
TTicks HighPrecisionResolution;
};
/** Get advanced information on the used timers.
*/
static void probeTimerInfo(CTimerInfo &result);
/** Return the number of second since midnight (00:00:00), January 1, 1970,
* coordinated universal time, according to the system clock.

View file

@ -32,9 +32,145 @@
#include "nel/misc/time_nl.h"
#include "nel/misc/sstring.h"
#include <nel/misc/thread.h>
namespace NLMISC
{
void CTime::probeTimerInfo(CTime::CTimerInfo &result)
{
breakable
{
#ifdef NL_OS_WINDOWS
LARGE_INTEGER winPerfFreq;
LARGE_INTEGER winPerfCount;
DWORD lowResTime;
if (!QueryPerformanceFrequency(&winPerfFreq))
{
nldebug("Cannot query performance frequency");
result.IsHighPrecisionAvailable = false;
}
else
{
result.HighPrecisionResolution = winPerfFreq.QuadPart;
}
if (winPerfFreq.QuadPart == 1000)
{
nldebug("Higher precision timer not available, OS defaulted to GetTickCount");
result.IsHighPrecisionAvailable = false;
}
if (!QueryPerformanceCounter(&winPerfCount))
{
nldebug("Cannot query performance counter");
result.IsHighPrecisionAvailable = false;
result.HighPrecisionResolution = 1000;
}
if (!result.IsHighPrecisionAvailable)
{
lowResTime = timeGetTime();
}
#else
// nldebug("Probe of timer info not implemented");
result.IsHighPrecisionAvailable = false;
result.RequiresSingleCore = true;
break;
#endif
uint64 cpuMask = IProcess::getCurrentProcess()->getCPUMask();
uint64 threadMask = IThread::getCurrentThread()->getCPUMask();
#ifdef NL_OS_WINDOWS
#else
TTicks timerFrequency = 0;
#endif
uint identical = 0; // Identical stamps may indicate the os handling backwards glitches.
uint backwards = 0; // Happens when the timers are not always in sync and the implementation is faulty.
uint regular = 0; // How many times the number advanced normally.
uint skipping = 0; // Does not really mean anything necessarily.
uint frequencybug = 0; // Should never happen.
// uint badcore = 0; // Affinity does not work.
// Cycle 32 times trough all cores, and verify if the timing remains consistent.
for (uint i = 32; i; --i)
{
uint64 currentBit = 1;
for (uint j = 64; j; --j)
{
if (cpuMask & currentBit)
{
IThread::getCurrentThread()->setCPUMask(currentBit);
#ifdef NL_OS_WINDOWS
// Make sure the thread is rescheduled.
SwitchToThread();
Sleep(0);
// Verify the core
/* Can only verify on 2003, Vista and higher.
if (1 << GetCurrentProcessorNumber() != currentBit)
++badcore;
*/
// Check if the timer is still sane.
if (result.IsHighPrecisionAvailable)
{
LARGE_INTEGER winPerfFreqN;
LARGE_INTEGER winPerfCountN;
QueryPerformanceFrequency(&winPerfFreqN);
if (winPerfFreqN.QuadPart != winPerfFreq.QuadPart)
++frequencybug;
QueryPerformanceCounter(&winPerfCountN);
if (winPerfCountN.QuadPart == winPerfCount.QuadPart)
++identical;
if (winPerfCountN.QuadPart < winPerfCount.QuadPart || winPerfCountN.QuadPart - winPerfCount.QuadPart < 0)
++backwards;
if (winPerfCountN.QuadPart - winPerfCount.QuadPart > winPerfFreq.QuadPart / 20) // 50ms skipping check
++skipping;
else if (winPerfCountN.QuadPart > winPerfCount.QuadPart)
++regular;
winPerfCount.QuadPart = winPerfCountN.QuadPart;
}
else
{
DWORD lowResTimeN;
lowResTimeN = timeGetTime();
if (lowResTimeN == lowResTime)
++identical;
if (lowResTimeN < lowResTime || lowResTimeN - lowResTime < 0)
++backwards;
if (lowResTimeN - lowResTime > 50)
++skipping;
else if (lowResTimeN > lowResTime)
++regular;
lowResTime = lowResTimeN;
}
#endif
}
currentBit <<= 1;
}
}
IThread::getCurrentThread()->setCPUMask(threadMask);
nldebug("Timer resolution: %i Hz", (int)(result.HighPrecisionResolution));
nldebug("Time identical: %i, backwards: %i, regular: %i, skipping: %i, frequency bug: %i", identical, backwards, regular, skipping, frequencybug);
if (identical > regular)
nlwarning("The system timer is of relatively low resolution, you may experience issues");
if (backwards > 0 || frequencybug > 0)
{
nlwarning("The current system timer is not reliable across multiple cpu cores");
result.RequiresSingleCore = true;
}
else result.RequiresSingleCore = false;
if (result.HighPrecisionResolution == 14318180)
nldebug("Detected known HPET era timer frequency");
if (result.HighPrecisionResolution == 3579545)
nldebug("Detected known AHCI era timer frequency");
if (result.HighPrecisionResolution == 1193182)
nldebug("Detected known i8253/i8254 era timer frequency");
}
}
/* Return the number of second since midnight (00:00:00), January 1, 1970,
* coordinated universal time, according to the system clock.
* This values is the same on all computer if computers are synchronized (with NTP for example).

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@ -18,3 +18,5 @@ IF(WIN32)
ADD_SUBDIRECTORY(words_dic)
ENDIF(MFC_FOUND)
ENDIF(WIN32)
ADD_SUBDIRECTORY(probe_timers)

View file

@ -0,0 +1,9 @@
FILE(GLOB SRC *.cpp)
ADD_EXECUTABLE(nl_probe_timers ${SRC})
TARGET_LINK_LIBRARIES(nl_probe_timers nelmisc)
NL_DEFAULT_PROPS(nl_probe_timers "NeL, Tools, Misc: Probe Timers")
NL_ADD_RUNTIME_FLAGS(nl_probe_timers)
INSTALL(TARGETS nl_probe_timers RUNTIME DESTINATION bin COMPONENT toolsmisc)

View file

@ -0,0 +1,38 @@
// NeL - MMORPG Framework <http://dev.ryzom.com/projects/nel/>
// Copyright (C) 2012 by authors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "nel/misc/types_nl.h"
#include "nel/misc/time_nl.h"
using namespace NLMISC;
int main (int argc, char **argv)
{
for (uint i = 0; i < 8; ++i)
{
CTime::CTimerInfo timerInfo;
CTime::probeTimerInfo(timerInfo);
}
printf ("\nPress <return> to exit\n");
getchar ();
return EXIT_SUCCESS;
}