[WeakMemoryCache] Field-Trial: Make Reference from MemoryCache to Resource weak

third_party/WebKit/Source/core/fetch/MemoryCache.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
     License as published by the Free Software Foundation; either
     version 2 of the License, or (at your option) any later version.
 
     This library 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
     Library General Public License for more details.
 
     You should have received a copy of the GNU Library General Public License
     along with this library; see the file COPYING.LIB.  If not, write to
     the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
     Boston, MA 02110-1301, USA.
 */
 
 #include "core/fetch/MemoryCache.h"
 
 #include "platform/Logging.h"
+#include "platform/RuntimeEnabledFeatures.h"
 #include "platform/TraceEvent.h"
 #include "platform/weborigin/SecurityOrigin.h"
 #include "platform/weborigin/SecurityOriginHash.h"
 #include "public/platform/Platform.h"
 #include "wtf/Assertions.h"
 #include "wtf/CurrentTime.h"
 #include "wtf/MathExtras.h"
 #include "wtf/TemporaryChange.h"
 #include "wtf/text/CString.h"
 
@@ skipping 17 matching lines @@
 
 MemoryCache* replaceMemoryCacheForTesting(MemoryCache* cache)
 {
     memoryCache();
     MemoryCache* oldCache = gMemoryCache->release();
     *gMemoryCache = cache;
     MemoryCacheDumpProvider::instance()->setMemoryCache(cache);
     return oldCache;
 }
 
+MemoryCacheEntry::MemoryCacheEntry(Resource* resource)
+    : m_inLiveDecodedResourcesList(false)

[yhirano, 2016/05/30 08:13:24]

[optional] I prefer member initialization at their definitions if initialized
with constants.

[hiroshige, 2016/06/01 02:25:14]

This CL is to be reverted on canary, so I prefer not doing this at this time to
keep changes a little small.

+    , m_accessCount(0)
+    , m_lastDecodedAccessTime(0.0)
+    , m_previousInLiveResourcesList(nullptr)
+    , m_nextInLiveResourcesList(nullptr)
+    , m_previousInAllResourcesList(nullptr)
+    , m_nextInAllResourcesList(nullptr)
+{
+    if (RuntimeEnabledFeatures::weakMemoryCacheEnabled())
+        m_resourceWeak = resource;
+    else
+        m_resource = resource;
+}
+
 DEFINE_TRACE(MemoryCacheEntry)
 {
     visitor->trace(m_resource);
+    visitor->trace(m_resourceWeak);
     visitor->trace(m_previousInLiveResourcesList);
     visitor->trace(m_nextInLiveResourcesList);
     visitor->trace(m_previousInAllResourcesList);
     visitor->trace(m_nextInAllResourcesList);
 }
 
 void MemoryCacheEntry::dispose()
 {
     m_resource.clear();
+    m_resourceWeak.clear();
 }
 
 Resource* MemoryCacheEntry::resource()
 {
+    if (RuntimeEnabledFeatures::weakMemoryCacheEnabled())
+        return m_resourceWeak.get();
     return m_resource.get();
 }
 
 DEFINE_TRACE(MemoryCacheLRUList)
 {
     visitor->trace(m_head);
     visitor->trace(m_tail);
 }
 
 inline MemoryCache::MemoryCache()
@@ skipping 67 matching lines @@
     }
     return m_resourceMaps.get(cacheIdentifier);
 }
 
 void MemoryCache::add(Resource* resource)
 {
     ASSERT(WTF::isMainThread());
     ASSERT(resource->url().isValid());
     ResourceMap* resources = ensureResourceMap(resource->cacheIdentifier());
     KURL url = removeFragmentIdentifierIfNeeded(resource->url());
-    RELEASE_ASSERT(!resources->contains(url));
+    RELEASE_ASSERT(!contains(resource));
     resources->set(url, MemoryCacheEntry::create(resource));
     update(resource, 0, resource->size(), true);
 
     WTF_LOG(ResourceLoading, "MemoryCache::add Added '%s', resource %p\n", resource->url().getString().latin1().data(), resource);
 }
 
 void MemoryCache::remove(Resource* resource)
 {
     // The resource may have already been removed by someone other than our caller,
     // who needed a fresh copy for a reload.
@@ skipping 29 matching lines @@
         return nullptr;
     return resource;
 }
 
 HeapVector<Member<Resource>> MemoryCache::resourcesForURL(const KURL& resourceURL)
 {
     ASSERT(WTF::isMainThread());
     KURL url = removeFragmentIdentifierIfNeeded(resourceURL);
     HeapVector<Member<Resource>> results;
     for (const auto& resourceMapIter : m_resourceMaps) {
-        if (MemoryCacheEntry* entry = resourceMapIter.value->get(url))
-            results.append(entry->resource());
+        if (MemoryCacheEntry* entry = resourceMapIter.value->get(url)) {
+            Resource* resource = entry->resource();
+            if (resource)
+                results.append(resource);
+        }
     }
     return results;
 }
 
 size_t MemoryCache::deadCapacity() const
 {
     // Dead resource capacity is whatever space is not occupied by live resources, bounded by an independent minimum and maximum.
     size_t capacity = m_capacity - std::min(m_liveSize, m_capacity); // Start with available capacity.
     capacity = std::max(capacity, m_minDeadCapacity); // Make sure it's above the minimum.
     capacity = std::min(capacity, m_maxDeadCapacity); // Make sure it's below the maximum.
@@ skipping 24 matching lines @@
     // The list might not be sorted by the m_lastDecodedFrameTimeStamp. The impact
     // of this weaker invariant is minor as the below if statement to check the
     // elapsedTime will evaluate to false as the current time will be a lot
     // greater than the current->m_lastDecodedFrameTimeStamp.
     // For more details see: https://bugs.webkit.org/show_bug.cgi?id=30209
 
     MemoryCacheEntry* current = m_liveDecodedResources.m_tail;
     while (current) {
         Resource* resource = current->resource();
         MemoryCacheEntry* previous = current->m_previousInLiveResourcesList;
+        if (!resource) {
+            current = previous;
+            continue;
+        }
         ASSERT(resource->hasClientsOrObservers());
 
         if (resource->isLoaded() && resource->decodedSize()) {
             // Check to see if the remaining resources are too new to prune.
             double elapsedTime = m_pruneFrameTimeStamp - current->m_lastDecodedAccessTime;
             if (strategy == AutomaticPrune && elapsedTime < m_delayBeforeLiveDecodedPrune)
                 return;
 
             // Destroy our decoded data if possible. This will remove us
             // from m_liveDecodedResources, and possibly move us to a
@@ skipping 85 matching lines @@
     m_maxDeadCapacity = maxDeadBytes;
     m_maxDeferredPruneDeadCapacity = cDeferredPruneDeadCapacityFactor * maxDeadBytes;
     m_capacity = totalBytes;
     prune();
 }
 
 void MemoryCache::evict(MemoryCacheEntry* entry)
 {
     ASSERT(WTF::isMainThread());
 
     Resource* resource = entry->resource();

[yhirano, 2016/05/30 08:13:24]

Can |resource| be null? If not, can you put an assertion?

[hiroshige, 2016/06/01 02:25:14]

I think |resource| should be non-null here (because call sites contains direct
null checks of |resource()|, or null checks of getEntryForResource(), which
returns null when |resource()| is null).
I added an assertion.

     WTF_LOG(ResourceLoading, "Evicting resource %p for '%s' from cache", resource, resource->url().getString().latin1().data());
     // The resource may have already been removed by someone other than our caller,
     // who needed a fresh copy for a reload. See <http://bugs.webkit.org/show_bug.cgi?id=12479#c6>.
     update(resource, resource->size(), 0, false);
     removeFromLiveDecodedResourcesList(entry);
 
     ResourceMap* resources = m_resourceMaps.get(resource->cacheIdentifier());
     ASSERT(resources);
     KURL url = removeFragmentIdentifierIfNeeded(resource->url());
     ResourceMap::iterator it = resources->find(url);
     ASSERT(it != resources->end());
 
     MemoryCacheEntry* entryPtr = it->value;
     resources->remove(it);
     if (entryPtr)
         entryPtr->dispose();
 }
 
 MemoryCacheEntry* MemoryCache::getEntryForResource(const Resource* resource) const
 {
-    if (resource->url().isNull() || resource->url().isEmpty())
+    if (!resource || resource->url().isNull() || resource->url().isEmpty())
         return nullptr;
     ResourceMap* resources = m_resourceMaps.get(resource->cacheIdentifier());
     if (!resources)
         return nullptr;
     KURL url = removeFragmentIdentifierIfNeeded(resource->url());
     MemoryCacheEntry* entry = resources->get(url);
     if (!entry || entry->resource() != resource)
         return nullptr;
     return entry;
 }
@@ skipping 192 matching lines @@
     encodedSizeDuplicatedInDataURLs += o->url().protocolIsData() ? o->encodedSize() : 0;
     purgeableSize += purgeable ? pageSize : 0;
 }
 
 MemoryCache::Statistics MemoryCache::getStatistics()
 {
     Statistics stats;
     for (const auto& resourceMapIter : m_resourceMaps) {
         for (const auto& resourceIter : *resourceMapIter.value) {
             Resource* resource = resourceIter.value->resource();
+            if (!resource)
+                continue;
             switch (resource->getType()) {
             case Resource::Image:
                 stats.images.addResource(resource);
                 break;
             case Resource::CSSStyleSheet:
                 stats.cssStyleSheets.addResource(resource);
                 break;
             case Resource::Script:
                 stats.scripts.addResource(resource);
                 break;
@@ skipping 16 matching lines @@
 {
     while (true) {
         ResourceMapIndex::iterator resourceMapIter = m_resourceMaps.begin();
         if (resourceMapIter == m_resourceMaps.end())
             break;
         ResourceMap* resources = resourceMapIter->value.get();
         while (true) {
             ResourceMap::iterator resourceIter = resources->begin();
             if (resourceIter == resources->end())
                 break;
-            evict(resourceIter->value.get());
+            if (resourceIter->value->resource())
+                evict(resourceIter->value.get());
+            else
+                resources->remove(resourceIter);
         }
         m_resourceMaps.remove(resourceMapIter);
     }
 }
 
 void MemoryCache::prune(Resource* justReleasedResource)
 {
     TRACE_EVENT0("renderer", "MemoryCache::prune()");
 
     if (m_inPruneResources)
@@ skipping 73 matching lines @@
 void MemoryCache::updateFramePaintTimestamp()
 {
     m_lastFramePaintTimeStamp = currentTime();
 }
 
 bool MemoryCache::onMemoryDump(WebMemoryDumpLevelOfDetail levelOfDetail, WebProcessMemoryDump* memoryDump)
 {
     for (const auto& resourceMapIter : m_resourceMaps) {
         for (const auto& resourceIter : *resourceMapIter.value) {
             Resource* resource = resourceIter.value->resource();
-            resource->onMemoryDump(levelOfDetail, memoryDump);
+            if (resource)
+                resource->onMemoryDump(levelOfDetail, memoryDump);
         }
     }
     return true;
 }
 
 bool MemoryCache::isInSameLRUListForTest(const Resource* x, const Resource* y)
 {
     MemoryCacheEntry* ex = getEntryForResource(x);
     MemoryCacheEntry* ey = getEntryForResource(y);
     ASSERT(ex);
@@ skipping 28 matching lines @@
 void MemoryCache::dumpLRULists(bool includeLive) const
 {
     printf("LRU-SP lists in eviction order (Kilobytes decoded, Kilobytes encoded, Access count, Referenced, isPurgeable):\n");
 
     int size = m_allResources.size();
     for (int i = size - 1; i >= 0; i--) {
         printf("\n\nList %d: ", i);
         MemoryCacheEntry* current = m_allResources[i].m_tail;
         while (current) {
             Resource* currentResource = current->resource();
-            if (includeLive || !currentResource->hasClientsOrObservers())
+            if (currentResource && (includeLive || !currentResource->hasClientsOrObservers()))
                 printf("(%.1fK, %.1fK, %uA, %dR, %d); ", currentResource->decodedSize() / 1024.0f, (currentResource->encodedSize() + currentResource->overheadSize()) / 1024.0f, current->m_accessCount, currentResource->hasClientsOrObservers(), currentResource->isPurgeable());
 
             current = current->m_previousInAllResourcesList;
         }
     }
 }
 
 #endif // MEMORY_CACHE_STATS
 
 } // namespace blink