Add framework of MemoryPurger, a class to dump memory from everywhere possible. Currently does nothing.

This also adds a "Purge memory" button to the task manager when run with --purge-memory-button, which can be used to test the functionality.

BUG=23400
TEST=Run with --purge-memory-button, open the task manager and see a new button.  Click it to toggle it to "Reset purge", and click again to toggle back.
Review URL: http://codereview.chromium.org/259003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@27751 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 61 insertions, 0 deletions

diff --git a/chrome/browser/memory_purger.cc b/chrome/browser/memory_purger.cc
new file mode 100644
index 0000000..2fc5b9e
--- /dev/null
+++ b/chrome/browser/memory_purger.cc
@@ -0,0 +1,61 @@
+// Copyright (c) 2009 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 "chrome/browser/memory_purger.h"
+
+#include "base/singleton.h"
+
+// static
+MemoryPurger* MemoryPurger::GetSingleton() {
+  return Singleton<MemoryPurger>::get();
+}
+
+void MemoryPurger::OnSuspend() {
+  // TODO:
+  //
+  // * For the browser process:
+  //   * Commit all the sqlite databases and unload them from memory; at the
+  // very least, do this with the history system, then use the prefetch trick to
+  // reload it on wake.
+  //   * Repeatedly call the V8 idle notification until it returns true
+  // ("nothing more to free").  Note that it makes more sense to do this than to
+  // implement a new "delete everything" pass because object references make it
+  // difficult to free everything possible in just one pass.
+  //   * Dump the backing stores.
+  //   * Destroy the spellcheck object.
+  //   * Tell tcmalloc to free everything it can.  (This is vague since it's not
+  // clear to me what this means; Jim, Mike, and Anton will know more here.
+  // Also, do we need to do this in each renderer process too?)
+  //
+  // * For each renderer process:
+  //   * Repeatedly call the V8 idle notification until it returns true.
+  //   * Tell the WebCore cache manager to set its global limit to 0, which
+  // should flush the image/script/css/etc. caches.
+  //   * Destroy the WebCore glyph caches.
+  //   * Tell tcmalloc to free everything it can.
+  //
+  // Concern: If we tell a bunch of renderer processes to destroy their data,
+  // they may have to page everything in to do it, which could end up
+  // overflowing the amount of time we have to work with.
+}
+
+void MemoryPurger::OnResume() {
+  // TODO:
+  //
+  // * For the browser process:
+  //   * Reload the history system and any other needed sqlite databases.
+  //
+  // * For each renderer process:
+  //   * Reset the WebCore cache manager global limit to the default.
+}
+
+MemoryPurger::MemoryPurger() {
+  base::SystemMonitor::Get()->AddObserver(this);
+}
+
+MemoryPurger::~MemoryPurger() {
+  base::SystemMonitor* system_monitor = base::SystemMonitor::Get();
+  if (system_monitor)
+    system_monitor->RemoveObserver(this);
+}