void MemoryPressureHandler::install()
{
if (m_installed || m_holdOffTimer.isActive())
return;
if (!tryEnsureEventFD())
return;
m_eventFDPoller = std::make_unique<EventFDPoller>(m_eventFD.value(), [this] {
// FIXME: Current memcg does not provide any way for users to know how serious the memory pressure is.
// So we assume all notifications from memcg are critical for now. If memcg had better inferfaces
// to get a detailed memory pressure level in the future, we should update here accordingly.
bool critical = true;
if (ReliefLogger::loggingEnabled())
LOG(MemoryPressure, "Got memory pressure notification (%s)", critical ? "critical" : "non-critical");
setUnderMemoryPressure(critical);
if (isMainThread())
respondToMemoryPressure(critical ? Critical::Yes : Critical::No);
else
RunLoop::main().dispatch([this, critical] { respondToMemoryPressure(critical ? Critical::Yes : Critical::No); });
});
if (ReliefLogger::loggingEnabled() && isUnderMemoryPressure())
LOG(MemoryPressure, "System is no longer under memory pressure.");
setUnderMemoryPressure(false);
m_installed = true;
}
void MemoryPressureHandler::releaseCriticalMemory(Synchronous synchronous)
{
{
ReliefLogger log("Empty the PageCache");
// Right now, the only reason we call release critical memory while not under memory pressure is if the process is about to be suspended.
PruningReason pruningReason = isUnderMemoryPressure() ? PruningReason::MemoryPressure : PruningReason::ProcessSuspended;
PageCache::singleton().pruneToSizeNow(0, pruningReason);
}
{
ReliefLogger log("Prune MemoryCache live resources");
MemoryCache::singleton().pruneLiveResourcesToSize(0);
}
{
ReliefLogger log("Drain CSSValuePool");
CSSValuePool::singleton().drain();
}
{
ReliefLogger log("Discard StyleResolvers");
Vector<RefPtr<Document>> documents;
copyToVector(Document::allDocuments(), documents);
for (auto& document : documents)
document->clearStyleResolver();
}
{
ReliefLogger log("Discard all JIT-compiled code");
GCController::singleton().deleteAllCode();
}
{
ReliefLogger log("Invalidate font cache");
FontCache::singleton().invalidate();
}
#if ENABLE(VIDEO)
{
ReliefLogger log("Dropping buffered data from paused media elements");
for (auto* mediaElement: HTMLMediaElement::allMediaElements()) {
if (mediaElement->paused())
mediaElement->purgeBufferedDataIfPossible();
}
}
#endif
if (synchronous == Synchronous::Yes) {
ReliefLogger log("Collecting JavaScript garbage");
GCController::singleton().garbageCollectNow();
} else
GCController::singleton().garbageCollectNowIfNotDoneRecently();
}
void MemoryPressureHandler::releaseCriticalMemory(Synchronous synchronous)
{
{
ReliefLogger log("Empty the PageCache");
// Right now, the only reason we call release critical memory while not under memory pressure is if the process is about to be suspended.
PruningReason pruningReason = isUnderMemoryPressure() ? PruningReason::MemoryPressure : PruningReason::ProcessSuspended;
PageCache::singleton().pruneToSizeNow(0, pruningReason);
}
{
ReliefLogger log("Prune MemoryCache live resources");
MemoryCache::singleton().pruneLiveResourcesToSize(0, /*shouldDestroyDecodedDataForAllLiveResources*/ true);
}
{
ReliefLogger log("Drain CSSValuePool");
CSSValuePool::singleton().drain();
}
{
ReliefLogger log("Discard StyleResolvers");
Vector<RefPtr<Document>> documents;
copyToVector(Document::allDocuments(), documents);
for (auto& document : documents)
document->clearStyleResolver();
}
{
ReliefLogger log("Discard all JIT-compiled code");
GCController::singleton().deleteAllCode();
}
#if ENABLE(VIDEO)
{
ReliefLogger log("Dropping buffered data from paused media elements");
for (auto* mediaElement: HTMLMediaElement::allMediaElements()) {
if (mediaElement->paused())
mediaElement->purgeBufferedDataIfPossible();
}
}
#endif
if (synchronous == Synchronous::Yes) {
ReliefLogger log("Collecting JavaScript garbage");
GCController::singleton().garbageCollectNow();
} else
GCController::singleton().garbageCollectNowIfNotDoneRecently();
// We reduce tiling coverage while under memory pressure, so make sure to drop excess tiles ASAP.
Page::forEachPage([](Page& page) {
page.chrome().client().scheduleCompositingLayerFlush();
});
}
void MemoryPressureHandler::install()
{
if (m_installed)
return;
m_eventFD = eventfd(0, EFD_CLOEXEC);
if (m_eventFD == -1) {
LOG(MemoryPressure, "eventfd() failed: %m");
return;
}
m_pressureLevelFD = open(s_cgroupMemoryPressureLevel, O_CLOEXEC | O_RDONLY);
if (m_pressureLevelFD == -1) {
logErrorAndCloseFDs("Failed to open memory.pressure_level");
return;
}
int fd = open(s_cgroupEventControl, O_CLOEXEC | O_WRONLY);
if (fd == -1) {
logErrorAndCloseFDs("Failed to open cgroup.event_control");
return;
}
char line[128] = {0, };
if (snprintf(line, sizeof(line), "%d %d low", m_eventFD, m_pressureLevelFD) < 0
|| write(fd, line, strlen(line) + 1) < 0) {
logErrorAndCloseFDs("Failed to write cgroup.event_control");
close(fd);
return;
}
close(fd);
m_threadID = createThread(waitForMemoryPressureEvent, this, "WebCore: MemoryPressureHandler");
if (!m_threadID) {
logErrorAndCloseFDs("Failed to create a thread for MemoryPressureHandler");
return;
}
if (ReliefLogger::loggingEnabled() && isUnderMemoryPressure())
LOG(MemoryPressure, "System is no longer under memory pressure.");
setUnderMemoryPressure(false);
m_installed = true;
}
