void MemoryCache::prune(Resource* justReleasedResource)
{
TRACE_EVENT0("renderer", "MemoryCache::prune()");
if (m_inPruneResources)
return;
if (m_liveSize + m_deadSize <= m_capacity && m_maxDeadCapacity && m_deadSize <= m_maxDeadCapacity) // Fast path.
return;
// To avoid burdening the current thread with repetitive pruning jobs,
// pruning is postponed until the end of the current task. If it has
// been more than m_maxPruneDeferralDelay since the last prune,
// then we prune immediately.
// If the current thread's run loop is not active, then pruning will happen
// immediately only if it has been over m_maxPruneDeferralDelay
// since the last prune.
double currentTime = WTF::currentTime();
if (m_prunePending) {
if (currentTime - m_pruneTimeStamp >= m_maxPruneDeferralDelay) {
pruneNow(currentTime, AutomaticPrune);
}
} else {
if (currentTime - m_pruneTimeStamp >= m_maxPruneDeferralDelay) {
pruneNow(currentTime, AutomaticPrune); // Delay exceeded, prune now.
} else {
// Defer.
Platform::current()->currentThread()->addTaskObserver(this);
m_prunePending = true;
}
}
if (m_prunePending && m_deadSize > m_maxDeferredPruneDeadCapacity && justReleasedResource) {
// The following eviction does not respect LRU order, but it can be done
// immediately in constant time, as opposed to pruneDeadResources, which
// we would rather defer because it is O(N), which would make tear-down of N
// objects O(N^2) if we pruned immediately. This immediate eviction is a
// safeguard against runaway memory consumption by dead resources
// while a prune is pending.
// Main Resources in the cache are only substitue data that was
// precached and should not be evicted.
if (justReleasedResource->type() != Resource::MainResource) {
if (MemoryCacheEntry* entry = getEntryForResource(justReleasedResource))
evict(entry);
}
// As a last resort, prune immediately
if (m_deadSize > m_maxDeferredPruneDeadCapacity)
pruneNow(currentTime, AutomaticPrune);
}
}
void MemoryCache::didProcessTask()
{
// Perform deferred pruning
ASSERT(m_prunePending);
pruneNow(WTF::currentTime());
}
void MemoryCache::pruneAll()
{
double currentTime = WTF::currentTime();
pruneNow(currentTime, MaximalPrune);
}
