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/* Copyright (C) 2006 Constantin Kaplinsky. All Rights Reserved.
*
* This is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This software 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this software; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
* USA.
*/
//
// PollingScheduler class implementation.
//
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <string.h>
#include <stdlib.h>
#ifdef DEBUG
#include <stdio.h>
#endif
#include <x0vncserver/PollingScheduler.h>
PollingScheduler::PollingScheduler(int interval, int maxload)
{
setParameters(interval, maxload);
reset();
}
void PollingScheduler::setParameters(int interval, int maxload)
{
m_interval = interval;
m_maxload = maxload;
if (m_interval < 0) {
m_interval = 0;
}
if (m_maxload < 1) {
m_maxload = 1;
} else if (m_maxload > 100) {
m_maxload = 100;
}
}
void PollingScheduler::reset()
{
m_initialState = true;
}
bool PollingScheduler::isRunning()
{
return !m_initialState;
}
void PollingScheduler::newPass()
{
TimeMillis timeNow;
if (m_initialState) {
// First polling pass: initialize statistics.
m_initialState = false;
m_ratedDuration = 0;
m_sleeping = 0;
memset(m_errors, 0, sizeof(m_errors));
m_errorSum = 0;
m_errorAbsSum = 0;
memset(m_durations, 0, sizeof(m_durations));
m_durationSum = 0;
memset(m_slept, 0, sizeof(m_slept));
m_sleptSum = 0;
m_idx = 0;
m_count = 0;
} else {
// Stop sleeping if not yet.
if (m_sleeping)
sleepFinished();
// Update statistics on sleeping time and total pass duration.
int duration = timeNow.diffFrom(m_passStarted);
int oldest = m_durations[m_idx];
m_durations[m_idx] = duration;
m_durationSum = m_durationSum - oldest + duration;
oldest = m_slept[m_idx];
m_slept[m_idx] = m_sleptThisPass;
m_sleptSum = m_sleptSum - oldest + m_sleptThisPass;
// Compute and save the difference between actual and planned time.
int newError = duration - m_interval;
oldest = m_errors[m_idx];
m_errors[m_idx] = newError;
m_errorSum = m_errorSum - oldest + newError;
m_errorAbsSum = m_errorAbsSum - abs(oldest) + abs(newError);
//
// Below is the most important part.
// Compute desired duration of the upcoming polling pass.
//
// Estimation based on keeping up constant interval.
m_ratedDuration = m_interval - m_errorSum / 2;
// Estimations based on keeping up desired CPU load.
int optimalLoadDuration1 = 0;
int optimalLoadDuration8 = 0;
int optimalLoadDuration = 0;
if (m_count > 4) {
// Estimation 1 (use previous pass statistics).
optimalLoadDuration1 =
((duration - m_sleptThisPass) * 100 + m_maxload/2) / m_maxload;
if (m_count > 16) {
// Estimation 2 (use history of 8 previous passes).
optimalLoadDuration8 =
((m_durationSum - m_sleptSum) * 900 + m_maxload*4) / (m_maxload*8)
- m_durationSum;
// Mix the above two giving more priority to the first.
optimalLoadDuration =
(2 * optimalLoadDuration1 + optimalLoadDuration8) / 3;
} else {
optimalLoadDuration = optimalLoadDuration1;
}
}
#ifdef DEBUG
fprintf(stderr, "<est %3d,%3d,%d>\t",
m_ratedDuration, optimalLoadDuration1, optimalLoadDuration8);
#endif
// Choose final estimation.
if (m_ratedDuration < optimalLoadDuration) {
m_ratedDuration = optimalLoadDuration;
}
if (m_ratedDuration < 0) {
m_ratedDuration = 0;
} else if (m_ratedDuration > 500 && m_interval <= 100) {
m_ratedDuration = 500;
} else if (m_ratedDuration > 1000) {
m_ratedDuration = 1000;
}
#ifdef DEBUG
fprintf(stderr, "<final est %3d>\t", m_ratedDuration);
#endif
// Update ring buffer indexer (8 elements per each arrays).
m_idx = (m_idx + 1) & 7;
// Update pass counter.
m_count++;
}
m_passStarted = timeNow;
m_sleptThisPass = 0;
}
void PollingScheduler::sleepStarted()
{
if (m_initialState || m_sleeping)
return;
m_sleepStarted.update();
m_sleeping = true;
}
void PollingScheduler::sleepFinished()
{
if (m_initialState || !m_sleeping)
return;
TimeMillis timeNow;
m_sleptThisPass += timeNow.diffFrom(m_sleepStarted);
m_sleeping = false;
}
int PollingScheduler::millisRemaining() const
{
if (m_initialState)
return 0;
TimeMillis timeNow;
int elapsed = timeNow.diffFrom(m_passStarted);
if (elapsed > m_ratedDuration)
return 0;
return (m_ratedDuration - elapsed);
}
bool PollingScheduler::goodTimeToPoll() const
{
if (m_initialState)
return true;
// Average error (per 8 elements in the ring buffer).
int errorAvg = (m_errorAbsSum + 4) / 8;
// It's ok to poll earlier if new error is no more than half-average.
return (millisRemaining() <= errorAvg / 2);
}
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