Commit 7b4bb3f5 authored by Christopher Dykes's avatar Christopher Dykes Committed by Facebook Github Bot

std::chrono'ize EventBase::SmoothLoopTime

Summary: Modernizing for the future.

Reviewed By: yfeldblum

Differential Revision: D4375539

fbshipit-source-id: e3edf8dd6b77d3338f8cf58ed128bc5bce62da32
parent f65d8d2c
......@@ -90,7 +90,7 @@ EventBase::EventBase(bool enableTimeMeasurement)
, queue_(nullptr)
, fnRunner_(nullptr)
, maxLatency_(0)
, avgLoopTime_(2000000)
, avgLoopTime_(std::chrono::milliseconds(2000000))
, maxLatencyLoopTime_(avgLoopTime_)
, enableTimeMeasurement_(enableTimeMeasurement)
, nextLoopCnt_(uint64_t(-40)) // Early wrap-around so bugs will manifest soon
......@@ -136,7 +136,7 @@ EventBase::EventBase(event_base* evb, bool enableTimeMeasurement)
, queue_(nullptr)
, fnRunner_(nullptr)
, maxLatency_(0)
, avgLoopTime_(2000000)
, avgLoopTime_(std::chrono::milliseconds(2000000))
, maxLatencyLoopTime_(avgLoopTime_)
, enableTimeMeasurement_(enableTimeMeasurement)
, nextLoopCnt_(uint64_t(-40)) // Early wrap-around so bugs will manifest soon
......@@ -207,7 +207,7 @@ void EventBase::setMaxReadAtOnce(uint32_t maxAtOnce) {
// for exp(-1) decay.
void EventBase::setLoadAvgMsec(uint32_t ms) {
assert(enableTimeMeasurement_);
uint64_t us = 1000 * ms;
std::chrono::microseconds us = std::chrono::milliseconds(ms);
if (ms > 0) {
maxLatencyLoopTime_.setTimeInterval(us);
avgLoopTime_.setTimeInterval(us);
......@@ -313,8 +313,10 @@ bool EventBase::loopBody(int flags) {
startWork_;
idle = startWork_ - idleStart;
avgLoopTime_.addSample(idle, busy);
maxLatencyLoopTime_.addSample(idle, busy);
avgLoopTime_.addSample(std::chrono::microseconds(idle),
std::chrono::microseconds(busy));
maxLatencyLoopTime_.addSample(std::chrono::microseconds(idle),
std::chrono::microseconds(busy));
if (observer_) {
if (observerSampleCount_++ == observer_->getSampleRate()) {
......@@ -633,8 +635,9 @@ void EventBase::initNotificationQueue() {
fnRunner_->startConsumingInternal(this, queue_.get());
}
void EventBase::SmoothLoopTime::setTimeInterval(uint64_t timeInterval) {
expCoeff_ = -1.0/timeInterval;
void EventBase::SmoothLoopTime::setTimeInterval(
std::chrono::microseconds timeInterval) {
expCoeff_ = -1.0 / timeInterval.count();
VLOG(11) << "expCoeff_ " << expCoeff_ << " " << __PRETTY_FUNCTION__;
}
......@@ -642,29 +645,32 @@ void EventBase::SmoothLoopTime::reset(double value) {
value_ = value;
}
void EventBase::SmoothLoopTime::addSample(int64_t idle, int64_t busy) {
/*
* Position at which the busy sample is considered to be taken.
* (Allows to quickly skew our average without editing much code)
*/
enum BusySamplePosition {
RIGHT = 0, // busy sample placed at the end of the iteration
CENTER = 1, // busy sample placed at the middle point of the iteration
LEFT = 2, // busy sample placed at the beginning of the iteration
};
void EventBase::SmoothLoopTime::addSample(
std::chrono::microseconds idle,
std::chrono::microseconds busy) {
/*
* Position at which the busy sample is considered to be taken.
* (Allows to quickly skew our average without editing much code)
*/
enum BusySamplePosition {
RIGHT = 0, // busy sample placed at the end of the iteration
CENTER = 1, // busy sample placed at the middle point of the iteration
LEFT = 2, // busy sample placed at the beginning of the iteration
};
// See http://en.wikipedia.org/wiki/Moving_average#Exponential_moving_average
// and D676020 for more info on this calculation.
VLOG(11) << "idle " << idle << " oldBusyLeftover_ " << oldBusyLeftover_ <<
" idle + oldBusyLeftover_ " << idle + oldBusyLeftover_ <<
" busy " << busy << " " << __PRETTY_FUNCTION__;
VLOG(11) << "idle " << idle.count() << " oldBusyLeftover_ "
<< oldBusyLeftover_.count() << " idle + oldBusyLeftover_ "
<< (idle + oldBusyLeftover_).count() << " busy " << busy.count()
<< " " << __PRETTY_FUNCTION__;
idle += oldBusyLeftover_ + busy;
oldBusyLeftover_ = (busy * BusySamplePosition::CENTER) / 2;
idle -= oldBusyLeftover_;
double coeff = exp(idle * expCoeff_);
double coeff = exp(idle.count() * expCoeff_);
value_ *= coeff;
value_ += (1.0 - coeff) * busy;
value_ += (1.0 - coeff) * busy.count();
}
bool EventBase::nothingHandledYet() const noexcept {
......
......@@ -519,17 +519,19 @@ class EventBase : private boost::noncopyable,
class SmoothLoopTime {
public:
explicit SmoothLoopTime(uint64_t timeInterval)
: expCoeff_(-1.0/timeInterval)
, value_(0.0)
, oldBusyLeftover_(0) {
explicit SmoothLoopTime(std::chrono::microseconds timeInterval)
: expCoeff_(-1.0 / timeInterval.count()),
value_(0.0),
oldBusyLeftover_(0) {
VLOG(11) << "expCoeff_ " << expCoeff_ << " " << __PRETTY_FUNCTION__;
}
void setTimeInterval(uint64_t timeInterval);
void setTimeInterval(std::chrono::microseconds timeInterval);
void reset(double value = 0.0);
void addSample(int64_t idle, int64_t busy);
void addSample(
std::chrono::microseconds idle,
std::chrono::microseconds busy);
double get() const {
return value_;
......@@ -540,9 +542,9 @@ class EventBase : private boost::noncopyable,
}
private:
double expCoeff_;
double value_;
int64_t oldBusyLeftover_;
double expCoeff_;
double value_;
std::chrono::microseconds oldBusyLeftover_;
};
void setObserver(const std::shared_ptr<EventBaseObserver>& observer) {
......
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