Purge browser cache for dom storage in a smarter way

content/browser/dom_storage/dom_storage_namespace.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/dom_storage/dom_storage_namespace.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
+#include "base/sys_info.h"
 #include "content/browser/dom_storage/dom_storage_area.h"
 #include "content/browser/dom_storage/dom_storage_task_runner.h"
 #include "content/browser/dom_storage/session_storage_database.h"
 #include "content/common/dom_storage/dom_storage_types.h"
 
 namespace content {
+namespace {
+// Limits on the cache size and number of areas in memory, over which the areas
+// are purged.
+#if defined(OS_ANDROID)
+const size_t kMaxStorageAreaCount = 20;
+const uint64_t kMaxCacheSize = 2 * 1024 * 1024;
+#else
+const size_t kMaxStorageAreaCount = 100;
+const uint64_t kMaxCacheSize = 20 * 1024 * 1024;
+#endif

[ssid, 2016/05/10 02:04:16]

Not sure if I should move these to dom_storage_types.h. Since these are just
used in this file.

+}  // namespace
 
 DOMStorageNamespace::DOMStorageNamespace(
     const base::FilePath& directory,
     DOMStorageTaskRunner* task_runner)
     : namespace_id_(kLocalStorageNamespaceId),
       directory_(directory),
       task_runner_(task_runner) {
 }
 
 DOMStorageNamespace::DOMStorageNamespace(
     int64_t namespace_id,
     const std::string& persistent_namespace_id,
     SessionStorageDatabase* session_storage_database,
     DOMStorageTaskRunner* task_runner)
     : namespace_id_(namespace_id),
       persistent_namespace_id_(persistent_namespace_id),
       task_runner_(task_runner),
-      session_storage_database_(session_storage_database) {
+      session_storage_database_(session_storage_database),
+      is_low_end_device_(base::SysInfo::IsLowEndDevice()) {
   DCHECK_NE(kLocalStorageNamespaceId, namespace_id);
 }
 
 DOMStorageNamespace::~DOMStorageNamespace() {
 }
 
 DOMStorageArea* DOMStorageNamespace::OpenStorageArea(const GURL& origin) {
   if (AreaHolder* holder = GetAreaHolder(origin)) {
     ++(holder->open_count_);
     return holder->area_.get();
@@ skipping 69 matching lines @@
 
 void DOMStorageNamespace::DeleteSessionStorageOrigin(const GURL& origin) {
   DOMStorageArea* area = OpenStorageArea(origin);
   area->FastClear();
   CloseStorageArea(area);
 }
 
 void DOMStorageNamespace::PurgeMemory(PurgeOption option) {
   if (directory_.empty())
     return;  // We can't purge w/o backing on disk.
+
+  if (option == PURGE_IF_NEEDED) {
+    if (!ShouldPurgeMemory())
+      return;
+    option = PURGE_UNOPENED;
+  }
+
   AreaMap::iterator it = areas_.begin();
   while (it != areas_.end()) {
     const AreaHolder& holder = it->second;
 
     // We can't purge if there are changes pending.
     if (holder.area_->HasUncommittedChanges()) {
       if (holder.open_count_ == 0) {
          // Schedule an immediate commit so the next time we're asked to purge,
          // we can drop it from memory.
          holder.area_->ScheduleImmediateCommit();
       }
-      ++it;
+      it++;
       continue;
     }
 
     // If not in use, we can shut it down and remove
     // it from our collection entirely.
     if (holder.open_count_ == 0) {
       holder.area_->Shutdown();
       areas_.erase(it++);
       continue;
     }
 
     if (option == PURGE_AGGRESSIVE) {
       // If aggressive is true, we clear caches and such
       // for opened areas.
       holder.area_->PurgeMemory();
     }
-
-    ++it;
+    it++;
   }
 }
 
+bool DOMStorageNamespace::ShouldPurgeMemory() {
+  // Purging is done based on the cache sizes without including the database
+  // size since it can be expensive trying to estimate the sqlite usage for all
+  // databases.
+  size_t total_cache_size = 0;
+  size_t total_area_count = 0;
+  unsigned inactive_area_count = 0;
+  for (AreaMap::const_iterator it = areas_.begin(); it != areas_.end(); ++it) {
+    if (it->second.area_->IsLoadedInMemory()) {
+      total_cache_size += it->second.area_->map_usage_in_bytes();
+      ++total_area_count;
+      if (it->second.open_count_ == 0)
+        ++inactive_area_count;
+    }
+  }
+
+  // Purge caches of closed databases on low end devices.
+  if (is_low_end_device_ && inactive_area_count)
+    return true;
+
+  if (total_cache_size > kMaxCacheSize ||
+      total_area_count > kMaxStorageAreaCount)
+    return true;
+
+  return false;
+}
+
 void DOMStorageNamespace::Shutdown() {
   AreaMap::const_iterator it = areas_.begin();
   for (; it != areas_.end(); ++it)
     it->second.area_->Shutdown();
 }
 
 void DOMStorageNamespace::Flush() {
   for (auto& entry : areas_) {
     if (!entry.second.area_->HasUncommittedChanges())
       continue;
     entry.second.area_->ScheduleImmediateCommit();
   }
 }
 
-unsigned int DOMStorageNamespace::CountInMemoryAreas() const {
-  unsigned int area_count = 0;
-  for (AreaMap::const_iterator it = areas_.begin(); it != areas_.end(); ++it) {
-    if (it->second.area_->IsLoadedInMemory())
-      ++area_count;
-  }
-  return area_count;
-}
-
 void DOMStorageNamespace::OnMemoryDump(
     base::trace_event::ProcessMemoryDump* pmd) {
   DCHECK(task_runner_->IsRunningOnPrimarySequence());
   for (const auto& it : areas_)
     it.second.area_->OnMemoryDump(pmd);
 }
 
 void DOMStorageNamespace::GetOriginsWithAreas(
     std::vector<GURL>* origins) const {
   origins->clear();
@@ skipping 19 matching lines @@
     DOMStorageArea* area, int count)
     : area_(area), open_count_(count) {
 }
 
 DOMStorageNamespace::AreaHolder::AreaHolder(const AreaHolder& other) = default;
 
 DOMStorageNamespace::AreaHolder::~AreaHolder() {
 }
 
 }  // namespace content