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[Client] Detect main-thread event loop stalls (#7155)

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* [Client] Detect main-thread event loop stalls

LagMonitor ticks the GUI event loop every 500 ms and records gaps
beyond 2 s as stalls, warning with their duration and keeping a
bounded ring of recent records for diagnostics. Measurement uses a
monotonic QElapsedTimer so wall-clock steps and suspend do not
fabricate stalls. Recorded timestamps stay in wall time for
correlating with user reports.

Took 1 minute

Took 13 minutes


Took 2 minutes

* [Client] Rename LagMonitor constants to SCREAMING_SNAKE_CASE

Took 15 minutes

* [Client] Discard suspend-spanning gaps in LagMonitor

Windows counts sleep time in its monotonic clock, so a suspend would
fabricate one bogus stall per resume. Reset the clock on application
state changes and drop implausibly huge gaps; extract recordGap() for
testability.

Took 3 minutes

* [Client] Unit test LagMonitor stall recording

Drives recordGap() directly to cover the threshold, plausibility cap,
trim, and clear behavior without timing-dependent waits.

Took 36 seconds

---------

Co-authored-by: Lukas Brübach <Bruebach.Lukas@bdosecurity.de>
This commit is contained in:
BruebachL 2026-08-23 00:53:40 +02:00 • committed by GitHub
parent b91e872f5f
commit 88aa036f7e
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63
cockatrice/src/client/lag_monitor.cpp Normal file
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#include "lag_monitor.h"
#include <QCoreApplication>
#include <QEvent>
#include <QTimer>
LagMonitor::LagMonitor(QObject *parent) : QObject(parent)
{
qApp->installEventFilter(this);
timer = new QTimer(this);
timer->setInterval(TICK_INTERVAL_MS);
connect(timer, &QTimer::timeout, this, &LagMonitor::checkTick);
tickClock.start();
timer->start();
}
QList<LagMonitor::StallRecord> LagMonitor::recentStalls() const
{
return stalls;
}
void LagMonitor::clearStalls()
{
stalls.clear();
}
bool LagMonitor::eventFilter(QObject *obj, QEvent *event)
{
if (event->type() == QEvent::ApplicationStateChange) {
// The transition may span a suspend or an arbitrary unfocused period;
// discard the gap so it cannot be mistaken for a stall.
tickClock.restart();
}
return QObject::eventFilter(obj, event);
}
void LagMonitor::checkTick()
{
recordGap(tickClock.restart());
}
void LagMonitor::recordGap(qint64 gapMs)
{
if (gapMs <= STALL_THRESHOLD_MS) {
return;
}
if (gapMs > MAX_PLAUSIBLE_STALL_MS) {
qCDebug(LagMonitorLog, "Ignoring implausible %lld ms gap (likely suspend)", static_cast<long long>(gapMs));
return;
}
const StallRecord record{.timestampMsSinceEpoch = QDateTime::currentMSecsSinceEpoch(), .durationMs = gapMs};
stalls.append(record);
while (stalls.size() > MAX_RECORDED_STALLS) {
stalls.removeFirst();
}
qCWarning(LagMonitorLog, "Event loop stalled for %lld ms (threshold: %d ms)", static_cast<long long>(gapMs),
STALL_THRESHOLD_MS);
}