void MemoryCache::pruneLiveResources()
{
    unsigned capacity = liveCapacity();
    if (!m_liveSize || (capacity && m_liveSize <= capacity))
        return;

    unsigned targetSize = static_cast<unsigned>(capacity * cTargetPrunePercentage); // Cut by a percentage to avoid immediately pruning again.

    double currentTime = FrameView::currentPaintTimeStamp();
    if (!currentTime) // In case prune is called directly, outside of a Frame paint.
        currentTime = WTF::currentTime();

    // Destroy any decoded data in live objects that we can.
    // Start from the tail, since this is the lowest priority
    // and least recently accessed of the objects.

    // The list might not be sorted by the m_lastDecodedAccessTime. The impact
    // of this weaker invariant is minor as the below if statement to check the
    // elapsedTime will evaluate to false as the currentTime will be a lot
    // greater than the current->m_lastDecodedAccessTime.
    // For more details see: https://bugs.webkit.org/show_bug.cgi?id=30209

    // Start pruning from the lowest priority list.
    for (int priority = Resource::CacheLiveResourcePriorityLow; priority <= Resource::CacheLiveResourcePriorityHigh; ++priority) {
        Resource* current = m_liveDecodedResources[priority].m_tail;
        while (current) {
            Resource* prev = current->m_prevInLiveResourcesList;
            ASSERT(current->hasClients());
            if (current->isLoaded() && current->decodedSize()) {
                // Check to see if the remaining resources are too new to prune.
                double elapsedTime = currentTime - current->m_lastDecodedAccessTime;
                if (elapsedTime < m_delayBeforeLiveDecodedPrune)
                    return;

                // Destroy our decoded data. This will remove us from
                // m_liveDecodedResources, and possibly move us to a different LRU
                // list in m_allResources.
                current->destroyDecodedData();

                if (targetSize && m_liveSize <= targetSize)
                    return;
            }
            current = prev;
        }
    }
}
Example #2
0
void MemoryCache::pruneDeadResources()
{
    unsigned capacity = deadCapacity();
    if (!m_deadSize || (capacity && m_deadSize <= capacity))
        return;

    unsigned targetSize = static_cast<unsigned>(capacity * cTargetPrunePercentage); // Cut by a percentage to avoid immediately pruning again.

    int size = m_allResources.size();

    // See if we have any purged resources we can evict.
    for (int i = 0; i < size; i++) {
        Resource* current = m_allResources[i].m_tail;
        while (current) {
            Resource* prev = current->m_prevInAllResourcesList;
            if (current->wasPurged()) {
                ASSERT(!current->hasClients());
                ASSERT(!current->isPreloaded());
                evict(current);
            }
            current = prev;
        }
    }
    if (targetSize && m_deadSize <= targetSize)
        return;

    bool canShrinkLRULists = true;
    for (int i = size - 1; i >= 0; i--) {
        // Remove from the tail, since this is the least frequently accessed of the objects.
        Resource* current = m_allResources[i].m_tail;

        // First flush all the decoded data in this queue.
        while (current) {
            // Protect 'previous' so it can't get deleted during destroyDecodedData().
            ResourcePtr<Resource> previous = current->m_prevInAllResourcesList;
            ASSERT(!previous || previous->inCache());
            if (!current->hasClients() && !current->isPreloaded() && current->isLoaded()) {
                // Destroy our decoded data. This will remove us from
                // m_liveDecodedResources, and possibly move us to a different
                // LRU list in m_allResources.
                current->destroyDecodedData();

                if (targetSize && m_deadSize <= targetSize)
                    return;
            }
            // Decoded data may reference other resources. Stop iterating if 'previous' somehow got
            // kicked out of cache during destroyDecodedData().
            if (previous && !previous->inCache())
                break;
            current = previous.get();
        }

        // Now evict objects from this queue.
        current = m_allResources[i].m_tail;
        while (current) {
            ResourcePtr<Resource> previous = current->m_prevInAllResourcesList;
            ASSERT(!previous || previous->inCache());
            if (!current->hasClients() && !current->isPreloaded() && !current->isCacheValidator()) {
                evict(current);
                if (targetSize && m_deadSize <= targetSize)
                    return;
            }
            if (previous && !previous->inCache())
                break;
            current = previous.get();
        }

        // Shrink the vector back down so we don't waste time inspecting
        // empty LRU lists on future prunes.
        if (m_allResources[i].m_head)
            canShrinkLRULists = false;
        else if (canShrinkLRULists)
            m_allResources.resize(i);
    }
}