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Merge pull request #7810 from zzmp/perf/usleep

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Improve CPU performance of Win32 usleep
This commit is contained in:
Seth Alves 2016-05-05 18:23:31 -07:00
commit 16a5030159
3 changed files with 124 additions and 67 deletions
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143
interface/src/Util.cpp
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@ -131,71 +131,102 @@ const glm::vec3 randVector() {
// Do some basic timing tests and report the results // Do some basic timing tests and report the results
void runTimingTests() { void runTimingTests() {
// How long does it take to make a call to get the time? // How long does it take to make a call to get the time?
const int numTimingTests = 3;
QElapsedTimer startTime;
float elapsedNSecs;
float elapsedUSecs;
qCDebug(interfaceapp, "numTimingTests: %d", numTimingTests);
startTime.start();
elapsedNSecs = (float)startTime.nsecsElapsed();
qCDebug(interfaceapp, "QElapsedTimer::nsecElapsed() ns: %f", (double)elapsedNSecs / numTimingTests);
// Test sleep functions for accuracy
startTime.start();
for (int i = 0; i < numTimingTests; i++) {
QThread::msleep(1);
}
elapsedNSecs = (float)startTime.nsecsElapsed();
qCDebug(interfaceapp, "QThread::msleep(1) ms: %f", (double)(elapsedNSecs / NSECS_PER_MSEC / numTimingTests));
startTime.start();
for (int i = 0; i < numTimingTests; i++) {
QThread::sleep(1);
}
elapsedNSecs = (float)startTime.nsecsElapsed();
qCDebug(interfaceapp, "QThread::sleep(1) s: %f", (double)(elapsedNSecs / NSECS_PER_MSEC / MSECS_PER_SECOND / numTimingTests));
const int numUsecTests = 1000;
startTime.start();
for (int i = 0; i < numUsecTests; i++) {
usleep(1);
}
elapsedNSecs = (float)startTime.nsecsElapsed();
qCDebug(interfaceapp, "usleep(1) (1000x) us: %f", (double)(elapsedNSecs / NSECS_PER_USEC / numUsecTests));
startTime.start();
for (int i = 0; i < numUsecTests; i++) {
usleep(10);
}
elapsedNSecs = (float)startTime.nsecsElapsed();
qCDebug(interfaceapp, "usleep(10) (1000x) us: %f", (double)(elapsedNSecs / NSECS_PER_USEC / numUsecTests));
startTime.start();
for (int i = 0; i < numUsecTests; i++) {
usleep(100);
}
elapsedNSecs = (float)startTime.nsecsElapsed();
qCDebug(interfaceapp, "usleep(100) (1000x) us: %f", (double)(elapsedNSecs / NSECS_PER_USEC / numUsecTests));
startTime.start();
for (int i = 0; i < numTimingTests; i++) {
usleep(1000);
}
elapsedNSecs = (float)startTime.nsecsElapsed();
qCDebug(interfaceapp, "usleep(1000) us: %f", (double)(elapsedNSecs / NSECS_PER_USEC / numTimingTests));
startTime.start();
for (int i = 0; i < numTimingTests; i++) {
usleep(1001);
}
elapsedNSecs = (float)startTime.nsecsElapsed();
qCDebug(interfaceapp, "usleep(1001) us: %f", (double)(elapsedNSecs / NSECS_PER_USEC / numTimingTests));
startTime.start();
for (int i = 0; i < numTimingTests; i++) {
usleep(1500);
}
elapsedNSecs = (float)startTime.nsecsElapsed();
qCDebug(interfaceapp, "usleep(1500) us: %f", (double)(elapsedNSecs / NSECS_PER_USEC / numTimingTests));
startTime.start();
usleep(15000);
elapsedNSecs = (float)startTime.nsecsElapsed();
qCDebug(interfaceapp, "usleep(15000) (1x) us: %f", (double)(elapsedNSecs / NSECS_PER_USEC));
const int numTests = 1000000; const int numTests = 1000000;
int* iResults = (int*)malloc(sizeof(int) * numTests); int* iResults = (int*)malloc(sizeof(int) * numTests);
float fTest = 1.0; float fTest = 1.0;
float* fResults = (float*)malloc(sizeof(float) * numTests); float* fResults = (float*)malloc(sizeof(float) * numTests);
QElapsedTimer startTime;
startTime.start();
float elapsedUsecs;
float NSEC_TO_USEC = 1.0f / 1000.0f;
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC;
qCDebug(interfaceapp, "QElapsedTimer::nsecElapsed() usecs: %f", (double)elapsedUsecs);
// Test sleep functions for accuracy
startTime.start();
QThread::msleep(1);
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC;
qCDebug(interfaceapp, "QThread::msleep(1) ms: %f", (double)(elapsedUsecs / 1000.0f));
startTime.start();
QThread::sleep(1);
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC;
qCDebug(interfaceapp, "QThread::sleep(1) ms: %f", (double)(elapsedUsecs / 1000.0f));
startTime.start();
usleep(1);
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC;
qCDebug(interfaceapp, "usleep(1) ms: %f", (double)(elapsedUsecs / 1000.0f));
startTime.start();
usleep(10);
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC;
qCDebug(interfaceapp, "usleep(10) ms: %f", (double)(elapsedUsecs / 1000.0f));
startTime.start();
usleep(100);
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC;
qCDebug(interfaceapp, "usleep(100) ms: %f", (double)(elapsedUsecs / 1000.0f));
startTime.start();
usleep(1000);
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC;
qCDebug(interfaceapp, "usleep(1000) ms: %f", (double)(elapsedUsecs / 1000.0f));
startTime.start();
usleep(15000);
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC;
qCDebug(interfaceapp, "usleep(15000) ms: %f", (double)(elapsedUsecs / 1000.0f));
// Random number generation // Random number generation
startTime.start(); startTime.start();
for (int i = 0; i < numTests; i++) { for (int i = 0; i < numTests; i++) {
iResults[i] = rand(); iResults[i] = rand();
} }
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC; elapsedUSecs = (float)startTime.nsecsElapsed() / NSECS_PER_USEC;
qCDebug(interfaceapp, "rand() stored in array usecs: %f, first result:%d", qCDebug(interfaceapp, "rand() stored in array usecs: %f, first result:%d",
(double)(elapsedUsecs / numTests), iResults[0]); (double)(elapsedUSecs / numTests), iResults[0]);
// Random number generation using randFloat() // Random number generation using randFloat()
startTime.start(); startTime.start();
for (int i = 0; i < numTests; i++) { for (int i = 0; i < numTests; i++) {
fResults[i] = randFloat(); fResults[i] = randFloat();
} }
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC; elapsedUSecs = (float)startTime.nsecsElapsed() / NSECS_PER_USEC;
qCDebug(interfaceapp, "randFloat() stored in array usecs: %f, first result: %f", qCDebug(interfaceapp, "randFloat() stored in array usecs: %f, first result: %f",
(double)(elapsedUsecs / numTests), (double)(fResults[0])); (double)(elapsedUSecs / numTests), (double)(fResults[0]));
free(iResults); free(iResults);
free(fResults); free(fResults);
@ -206,8 +237,8 @@ void runTimingTests() {
for (int i = 0; i < numTests; i++) { for (int i = 0; i < numTests; i++) {
fTest = powf(fTest, 0.5f); fTest = powf(fTest, 0.5f);
} }
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC; elapsedUSecs = (float)startTime.nsecsElapsed() / NSECS_PER_USEC;
qCDebug(interfaceapp, "powf(f, 0.5) usecs: %f", (double)(elapsedUsecs / (float) numTests)); qCDebug(interfaceapp, "powf(f, 0.5) usecs: %f", (double)(elapsedUSecs / (float) numTests));
// Vector Math // Vector Math
float distance; float distance;
@ -218,9 +249,9 @@ void runTimingTests() {
//float distanceSquared = glm::dot(temp, temp); //float distanceSquared = glm::dot(temp, temp);
distance = glm::distance(pointA, pointB); distance = glm::distance(pointA, pointB);
} }
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC; elapsedUSecs = (float)startTime.nsecsElapsed() / NSECS_PER_USEC;
qCDebug(interfaceapp, "vector math usecs: %f [%f usecs total for %d tests], last result:%f", qCDebug(interfaceapp, "vector math usecs: %f [%f usecs total for %d tests], last result:%f",
(double)(elapsedUsecs / (float) numTests), (double)elapsedUsecs, numTests, (double)distance); (double)(elapsedUSecs / (float) numTests), (double)elapsedUSecs, numTests, (double)distance);
// Vec3 test // Vec3 test
glm::vec3 vecA(randVector()), vecB(randVector()); glm::vec3 vecA(randVector()), vecB(randVector());
@ -231,9 +262,9 @@ void runTimingTests() {
glm::vec3 temp = vecA-vecB; glm::vec3 temp = vecA-vecB;
result = glm::dot(temp,temp); result = glm::dot(temp,temp);
} }
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC; elapsedUSecs = (float)startTime.nsecsElapsed() / NSECS_PER_USEC;
qCDebug(interfaceapp, "vec3 assign and dot() usecs: %f, last result:%f", qCDebug(interfaceapp, "vec3 assign and dot() usecs: %f, last result:%f",
(double)(elapsedUsecs / numTests), (double)result); (double)(elapsedUSecs / numTests), (double)result);
quint64 BYTE_CODE_MAX_TEST_VALUE = 99999999; quint64 BYTE_CODE_MAX_TEST_VALUE = 99999999;
@ -265,9 +296,9 @@ void runTimingTests() {
} }
} }
elapsedUsecs = (float)startTime.nsecsElapsed() * NSEC_TO_USEC; elapsedUSecs = (float)startTime.nsecsElapsed() / NSECS_PER_USEC;
qCDebug(interfaceapp) << "ByteCountCoded<quint64> usecs: " << elapsedUsecs qCDebug(interfaceapp) << "ByteCountCoded<quint64> usecs: " << elapsedUSecs
<< "per test:" << (double) (elapsedUsecs / tests) << "per test:" << (double) (elapsedUSecs / tests)
<< "tests:" << tests << "tests:" << tests
<< "failed:" << failed; << "failed:" << failed;
} }

1
libraries/shared/src/NumericalConstants.h
View file

@ -35,6 +35,7 @@ const float METERS_PER_CENTIMETER = 0.01f;
const float METERS_PER_MILLIMETER = 0.001f; const float METERS_PER_MILLIMETER = 0.001f;
const float MILLIMETERS_PER_METER = 1000.0f; const float MILLIMETERS_PER_METER = 1000.0f;
const quint64 NSECS_PER_USEC = 1000; const quint64 NSECS_PER_USEC = 1000;
const quint64 NSECS_PER_MSEC = 1000000;
const quint64 USECS_PER_MSEC = 1000; const quint64 USECS_PER_MSEC = 1000;
const quint64 MSECS_PER_SECOND = 1000; const quint64 MSECS_PER_SECOND = 1000;
const quint64 USECS_PER_SECOND = USECS_PER_MSEC * MSECS_PER_SECOND; const quint64 USECS_PER_SECOND = USECS_PER_MSEC * MSECS_PER_SECOND;

47
libraries/shared/src/SharedUtil.cpp
View file

@ -455,19 +455,44 @@ void printVoxelCode(unsigned char* voxelCode) {
} }
#ifdef _WIN32 #ifdef _WIN32
void usleep(int waitTime) { void usleep(int waitTime) {
const quint64 BUSY_LOOP_USECS = 2000; // Use QueryPerformanceCounter for least overhead
quint64 compTime = waitTime + usecTimestampNow(); LARGE_INTEGER now; // ticks
quint64 compTimeSleep = compTime - BUSY_LOOP_USECS; QueryPerformanceCounter(&now);
while (true) {
if (usecTimestampNow() < compTimeSleep) { static int64_t ticksPerSec = 0;
QThread::msleep(1); if (ticksPerSec == 0) {
} LARGE_INTEGER frequency;
if (usecTimestampNow() >= compTime) { QueryPerformanceFrequency(&frequency);
break; ticksPerSec = frequency.QuadPart;
} }
// order ops to avoid loss in precision
int64_t waitTicks = (ticksPerSec * waitTime) / USECS_PER_SECOND;
int64_t sleepTicks = now.QuadPart + waitTicks;
// Busy wait with sleep/yield where possible
while (true) {
QueryPerformanceCounter(&now);
if (now.QuadPart >= sleepTicks) {
break;
}
// Sleep if we have at least 1ms to spare
const int64_t MIN_SLEEP_USECS = 1000;
// msleep is allowed to overshoot, so give it a 100us berth
const int64_t MIN_SLEEP_USECS_BERTH = 100;
// order ops to avoid loss in precision
int64_t sleepFor = ((sleepTicks - now.QuadPart) * USECS_PER_SECOND) / ticksPerSec - MIN_SLEEP_USECS_BERTH;
if (sleepFor > MIN_SLEEP_USECS) {
Sleep((DWORD)(sleepFor / USECS_PER_MSEC));
// Yield otherwise
} else {
// Use Qt to delegate, as SwitchToThread is only supported starting with XP
QThread::yieldCurrentThread();
} }
} }
}
#endif #endif
// Inserts the value and key into three arrays sorted by the key array, the first array is the value, // Inserts the value and key into three arrays sorted by the key array, the first array is the value,