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Digital filter for adaptive timeout adjustment, needs trunk baking, makes things better so far (117061, r=pavlov, sr=jst).

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This commit is contained in:
brendan@mozilla.org
2002-02-18 00:10:55 +00:00
parent f364d677bd
commit 7ddb7b5acc
5 changed files with 200 additions and 112 deletions
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158
xpcom/threads/TimerThread.cpp
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@@ -43,19 +43,14 @@
NS_IMPL_THREADSAFE_ISUPPORTS1(TimerThread, nsIRunnable)
#undef ACCEPT_WRONG_TIMES
#ifdef ACCEPT_WRONG_TIMES
// allow the thread to wake up and process timers +/- 3ms of when they
// are really supposed to fire.
static const PRIntervalTime kThreeMS = PR_MillisecondsToInterval(3);
#endif
TimerThread::TimerThread() :
mCondVar(nsnull),
mLock(nsnull),
mCondVar(nsnull),
mProcessing(PR_FALSE),
mWaiting(PR_FALSE)
mWaiting(PR_FALSE),
mDelayLineCounter(0),
mMinTimerPeriod(0),
mTimeoutAdjustment(0)
{
NS_INIT_REFCNT();
}
@@ -119,79 +114,136 @@ nsresult TimerThread::Shutdown()
RemoveTimerInternal(timer);
}
}
mThread->Join(); // wait for the thread to die
return NS_OK;
}
// Keep track of how early (positive slack) or late (negative slack) timers
// are running, and use the filtered slack number to adaptively estimate how
// early timers should fire to be "on time".
void TimerThread::UpdateFilter(PRUint32 aDelay, PRIntervalTime aTimeout,
PRIntervalTime aNow)
{
PRInt32 slack = (PRInt32) (aTimeout - aNow);
double smoothSlack = 0;
PRUint32 i, filterLength;
static PRIntervalTime kFilterFeedbackMaxTicks =
PR_MillisecondsToInterval(FILTER_FEEDBACK_MAX);
if (slack > 0) {
if (slack > (PRInt32)kFilterFeedbackMaxTicks)
slack = kFilterFeedbackMaxTicks;
} else {
if (slack < -(PRInt32)kFilterFeedbackMaxTicks)
slack = -(PRInt32)kFilterFeedbackMaxTicks;
}
mDelayLine[mDelayLineCounter & DELAY_LINE_LENGTH_MASK] = slack;
if (++mDelayLineCounter < DELAY_LINE_LENGTH) {
// Startup mode: accumulate a full delay line before filtering.
PR_ASSERT(mTimeoutAdjustment == 0);
filterLength = 0;
} else {
// Past startup: compute number of filter taps based on mMinTimerPeriod.
if (mMinTimerPeriod == 0) {
mMinTimerPeriod = (aDelay != 0) ? aDelay : 1;
} else if (aDelay != 0 && aDelay < mMinTimerPeriod) {
mMinTimerPeriod = aDelay;
}
filterLength = (PRUint32) (FILTER_DURATION / mMinTimerPeriod);
if (filterLength > DELAY_LINE_LENGTH)
filterLength = DELAY_LINE_LENGTH;
else if (filterLength < 4)
filterLength = 4;
for (i = 1; i <= filterLength; i++)
smoothSlack += mDelayLine[(mDelayLineCounter-i) & DELAY_LINE_LENGTH_MASK];
smoothSlack /= filterLength;
// XXXbe do we need amplification? hacking a fudge factor, need testing...
mTimeoutAdjustment = (PRInt32) (smoothSlack * 1.5);
}
#ifdef DEBUG_TIMERS
if (PR_LOG_TEST(gTimerLog, PR_LOG_DEBUG)) {
PR_LOG(gTimerLog, PR_LOG_DEBUG,
("UpdateFilter: smoothSlack = %g, filterLength = %u\n",
smoothSlack, filterLength));
}
#endif
}
/* void Run(); */
NS_IMETHODIMP TimerThread::Run()
{
nsAutoLock lock(mLock);
mProcessing = PR_TRUE;
while (mProcessing) {
nsTimerImpl *theTimer = nsnull;
PRIntervalTime now = PR_IntervalNow();
nsTimerImpl *timer = nsnull;
if (mTimers.Count() > 0) {
nsAutoLock lock(mLock);
nsTimerImpl *timer = NS_STATIC_CAST(nsTimerImpl*, mTimers[0]);
timer = NS_STATIC_CAST(nsTimerImpl*, mTimers[0]);
PRIntervalTime itIsNow = PR_IntervalNow();
#ifdef ACCEPT_WRONG_TIMES
if (itIsNow + kThreeMS > timer->mTimeout - kThreeMS)
#else
if (itIsNow >= timer->mTimeout)
#endif
{
if (now >= timer->mTimeout + mTimeoutAdjustment) {
next:
RemoveTimerInternal(timer);
theTimer = timer;
NS_ADDREF(theTimer);
}
}
NS_ADDREF(timer);
// We release mLock around the Fire call, of course, to avoid deadlock.
lock.unlock();
if (theTimer) {
#ifdef DEBUG_TIMERS
if (PR_LOG_TEST(gTimerLog, PR_LOG_DEBUG)) {
PRIntervalTime now = PR_IntervalNow();
PR_LOG(gTimerLog, PR_LOG_DEBUG, ("Timer thread woke up %dms from when it was supposed to\n",
((now > theTimer->mTimeout) ? PR_IntervalToMilliseconds(now - theTimer->mTimeout) :
-(PRInt32)PR_IntervalToMilliseconds(theTimer->mTimeout - now))));
}
if (PR_LOG_TEST(gTimerLog, PR_LOG_DEBUG)) {
PR_LOG(gTimerLog, PR_LOG_DEBUG,
("Timer thread woke up %dms from when it was supposed to\n",
(now >= timer->mTimeout)
? PR_IntervalToMilliseconds(now - timer->mTimeout)
: -(PRInt32)PR_IntervalToMilliseconds(timer->mTimeout - now))
);
}
#endif
// We are going to let the call to Fire here handle the release of the timer so that
// we don't end up releasing the timer on the TimerThread
theTimer->Fire();
// We are going to let the call to Fire here handle the release of the
// timer so that we don't end up releasing the timer on the TimerThread
// instead of on the thread it targets.
timer->Fire();
timer = nsnull;
theTimer = nsnull;
lock.lock();
if (!mProcessing)
break;
// Update now, as Fire plus the locking may have taken a tick or two,
// and we may goto next below.
now = PR_IntervalNow();
}
}
nsAutoLock lock(mLock);
PRIntervalTime waitFor = PR_INTERVAL_NO_TIMEOUT;
if (mTimers.Count() > 0) {
PRIntervalTime now = PR_IntervalNow();
PRIntervalTime timeout = NS_STATIC_CAST(nsTimerImpl *, mTimers[0])->mTimeout;
timer = NS_STATIC_CAST(nsTimerImpl *, mTimers[0]);
#ifdef ACCEPT_WRONG_TIMES
if (timeout > now + kThreeMS)
#else
if (timeout > now)
#endif
waitFor = timeout - now;
else
waitFor = PR_INTERVAL_NO_WAIT;
PRIntervalTime timeout = timer->mTimeout + mTimeoutAdjustment;
// Don't wait at all (even for PR_INTERVAL_NO_WAIT) if the next timer is
// due now or overdue.
if (now >= timeout)
goto next;
waitFor = timeout - now;
}
#ifdef DEBUG_TIMERS
if (PR_LOG_TEST(gTimerLog, PR_LOG_DEBUG)) {
if (waitFor == PR_INTERVAL_NO_TIMEOUT)
PR_LOG(gTimerLog, PR_LOG_DEBUG, ("waiting for PR_INTERVAL_NO_TIMEOUT\n"));
else if (waitFor == PR_INTERVAL_NO_WAIT)
PR_LOG(gTimerLog, PR_LOG_DEBUG, ("waiting for PR_INTERVAL_NO_WAIT\n"));
PR_LOG(gTimerLog, PR_LOG_DEBUG,
("waiting for PR_INTERVAL_NO_TIMEOUT\n"));
else
PR_LOG(gTimerLog, PR_LOG_DEBUG, ("waiting for %u\n", PR_IntervalToMilliseconds(waitFor)));
PR_LOG(gTimerLog, PR_LOG_DEBUG,
("waiting for %u\n", PR_IntervalToMilliseconds(waitFor)));
}
#endif
@@ -243,7 +295,7 @@ PRInt32 TimerThread::AddTimerInternal(nsTimerImpl *aTimer)
PRInt32 i = 0;
for (; i < count; i++) {
nsTimerImpl *timer = NS_STATIC_CAST(nsTimerImpl *, mTimers[i]);
if (aTimer->mTimeout < timer->mTimeout) {
break;
}