// Copyright (c) 2011 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.
// This is the browser side of the cache manager, it tracks the activity of the
// render processes and allocates available memory cache resources.
#ifndef CHROME_BROWSER_RENDERER_HOST_WEB_CACHE_MANAGER_H_
#define CHROME_BROWSER_RENDERER_HOST_WEB_CACHE_MANAGER_H_
#include <list>
#include <map>
#include <set>
#include "base/basictypes.h"
#include "base/compiler_specific.h"
#include "base/gtest_prod_util.h"
#include "base/memory/weak_ptr.h"
#include "base/time/time.h"
#include "content/public/browser/notification_observer.h"
#include "content/public/browser/notification_registrar.h"
#include "third_party/WebKit/public/web/WebCache.h"
template<typename Type>
struct DefaultSingletonTraits;
class PrefRegistrySimple;
class WebCacheManager : public content::NotificationObserver {
friend class WebCacheManagerTest;
FRIEND_TEST_ALL_PREFIXES(WebCacheManagerBrowserTest, CrashOnceOnly);
public:
static void RegisterPrefs(PrefRegistrySimple* registry);
// Gets the singleton WebCacheManager object. The first time this method
// is called, a WebCacheManager object is constructed and returned.
// Subsequent calls will return the same object.
static WebCacheManager* GetInstance();
// When a render process is created, it registers itself with the cache
// manager host, causing the renderer to be allocated cache resources.
void Add(int renderer_id);
// When a render process ends, it removes itself from the cache manager host,
// freeing the manager to assign its cache resources to other renderers.
void Remove(int renderer_id);
// The cache manager assigns more cache resources to active renderer. When a
// renderer is active, it should inform the cache manager to receive more
// cache resources.
//
// When a renderer moves from being inactive to being active, the cache
// manager may decide to adjust its resource allocation, but it will delay
// the recalculation, allowing ObserveActivity to return quickly.
void ObserveActivity(int renderer_id);
// Periodically, renderers should inform the cache manager of their current
// statistics. The more up-to-date the cache manager's statistics, the
// better it can allocate cache resources.
void ObserveStats(
int renderer_id, const blink::WebCache::UsageStats& stats);
// The global limit on the number of bytes in all the in-memory caches.
size_t global_size_limit() const { return global_size_limit_; }
// Sets the global size limit, forcing a recalculation of cache allocations.
void SetGlobalSizeLimit(size_t bytes);
// Clears all in-memory caches.
void ClearCache();
// Clears all in-memory caches when a tab is reloaded or the user navigates
// to a different website.
void ClearCacheOnNavigation();
// content::NotificationObserver implementation:
virtual void Observe(int type,
const content::NotificationSource& source,
const content::NotificationDetails& details) OVERRIDE;
// Gets the default global size limit. This interrogates system metrics to
// tune the default size to the current system.
static size_t GetDefaultGlobalSizeLimit();
protected:
// The amount of idle time before we consider a tab to be "inactive"
static const int kRendererInactiveThresholdMinutes = 5;
// Keep track of some renderer information.
struct RendererInfo : blink::WebCache::UsageStats {
// The access time for this renderer.
base::Time access;
};
typedef std::map<int, RendererInfo> StatsMap;
// An allocation is the number of bytes a specific renderer should use for
// its cache.
typedef std::pair<int,size_t> Allocation;
// An allocation strategy is a list of allocations specifying the resources
// each renderer is permitted to consume for its cache.
typedef std::list<Allocation> AllocationStrategy;
// This class is a singleton. Do not instantiate directly.
WebCacheManager();
friend struct DefaultSingletonTraits<WebCacheManager>;
virtual ~WebCacheManager();
// Recomputes the allocation of cache resources among the renderers. Also
// informs the renderers of their new allocation.
void ReviseAllocationStrategy();
// Schedules a call to ReviseAllocationStrategy after a short delay.
void ReviseAllocationStrategyLater();
// The various tactics used as part of an allocation strategy. To decide
// how many resources a given renderer should be allocated, we consider its
// usage statistics. Each tactic specifies the function that maps usage
// statistics to resource allocations.
//
// Determining a resource allocation strategy amounts to picking a tactic
// for each renderer and checking that the total memory required fits within
// our |global_size_limit_|.
enum AllocationTactic {
// Ignore cache statistics and divide resources equally among the given
// set of caches.
DIVIDE_EVENLY,
// Allow each renderer to keep its current set of cached resources, with
// some extra allocation to store new objects.
KEEP_CURRENT_WITH_HEADROOM,
// Allow each renderer to keep its current set of cached resources.
KEEP_CURRENT,
// Allow each renderer to keep cache resources it believes are currently
// being used, with some extra allocation to store new objects.
KEEP_LIVE_WITH_HEADROOM,
// Allow each renderer to keep cache resources it believes are currently
// being used, but instruct the renderer to discard all other data.
KEEP_LIVE,
};
// Helper functions for devising an allocation strategy
// Add up all the stats from the given set of renderers and place the result
// in |stats|.
void GatherStats(const std::set<int>& renderers,
blink::WebCache::UsageStats* stats);
// Get the amount of memory that would be required to implement |tactic|
// using the specified allocation tactic. This function defines the
// semantics for each of the tactics.
static size_t GetSize(AllocationTactic tactic,
const blink::WebCache::UsageStats& stats);
// Attempt to use the specified tactics to compute an allocation strategy
// and place the result in |strategy|. |active_stats| and |inactive_stats|
// are the aggregate statistics for |active_renderers_| and
// |inactive_renderers_|, respectively.
//
// Returns |true| on success and |false| on failure. Does not modify
// |strategy| on failure.
bool AttemptTactic(AllocationTactic active_tactic,
const blink::WebCache::UsageStats& active_stats,
AllocationTactic inactive_tactic,
const blink::WebCache::UsageStats& inactive_stats,
AllocationStrategy* strategy);
// For each renderer in |renderers|, computes its allocation according to
// |tactic| and add the result to |strategy|. Any |extra_bytes_to_allocate|
// is divided evenly among the renderers.
void AddToStrategy(const std::set<int>& renderers,
AllocationTactic tactic,
size_t extra_bytes_to_allocate,
AllocationStrategy* strategy);
// Enact an allocation strategy by informing the renderers of their
// allocations according to |strategy|.
void EnactStrategy(const AllocationStrategy& strategy);
enum ClearCacheOccasion {
// Instructs to clear the cache instantly.
INSTANTLY,
// Instructs to clear the cache when a navigation takes place (this
// includes reloading a tab).
ON_NAVIGATION
};
// Inform all |renderers| to clear their cache.
void ClearRendererCache(const std::set<int>& renderers,
ClearCacheOccasion occation);
// Check to see if any active renderers have fallen inactive.
void FindInactiveRenderers();
// The global size limit for all in-memory caches.
size_t global_size_limit_;
// Maps every renderer_id our most recent copy of its statistics.
StatsMap stats_;
// Every renderer we think is still around is in one of these two sets.
//
// Active renderers are those renderers that have been active more recently
// than they have been inactive.
std::set<int> active_renderers_;
// Inactive renderers are those renderers that have been inactive more
// recently than they have been active.
std::set<int> inactive_renderers_;
base::WeakPtrFactory<WebCacheManager> weak_factory_;
content::NotificationRegistrar registrar_;
DISALLOW_COPY_AND_ASSIGN(WebCacheManager);
};
#endif // CHROME_BROWSER_RENDERER_HOST_WEB_CACHE_MANAGER_H_