1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "chrome/browser/renderer_host/web_cache_manager.h"
6
7 #include <algorithm>
8
9 #include "base/compiler_specific.h"
10 #include "base/memory/singleton.h"
11 #include "base/metrics/histogram.h"
12 #include "base/sys_info.h"
13 #include "base/time.h"
14 #include "chrome/browser/browser_process.h"
15 #include "chrome/browser/prefs/pref_service.h"
16 #include "chrome/common/chrome_constants.h"
17 #include "chrome/common/pref_names.h"
18 #include "chrome/common/render_messages.h"
19 #include "content/browser/renderer_host/render_process_host.h"
20 #include "content/common/notification_service.h"
21
22 using base::Time;
23 using base::TimeDelta;
24 using WebKit::WebCache;
25
26 static const unsigned int kReviseAllocationDelayMS = 200 /* milliseconds */;
27
28 // The default size limit of the in-memory cache is 8 MB
29 static const int kDefaultMemoryCacheSize = 8 * 1024 * 1024;
30
31 namespace {
32
GetDefaultCacheSize()33 int GetDefaultCacheSize() {
34 // Start off with a modest default
35 int default_cache_size = kDefaultMemoryCacheSize;
36
37 // Check how much physical memory the OS has
38 int mem_size_mb = base::SysInfo::AmountOfPhysicalMemoryMB();
39 if (mem_size_mb >= 1000) // If we have a GB of memory, set a larger default.
40 default_cache_size *= 4;
41 else if (mem_size_mb >= 512) // With 512 MB, set a slightly larger default.
42 default_cache_size *= 2;
43
44 UMA_HISTOGRAM_MEMORY_MB("Cache.MaxCacheSizeMB",
45 default_cache_size / 1024 / 1024);
46
47 return default_cache_size;
48 }
49
50 } // anonymous namespace
51
52 // static
RegisterPrefs(PrefService * prefs)53 void WebCacheManager::RegisterPrefs(PrefService* prefs) {
54 prefs->RegisterIntegerPref(prefs::kMemoryCacheSize, GetDefaultCacheSize());
55 }
56
57 // static
GetInstance()58 WebCacheManager* WebCacheManager::GetInstance() {
59 return Singleton<WebCacheManager>::get();
60 }
61
WebCacheManager()62 WebCacheManager::WebCacheManager()
63 : global_size_limit_(GetDefaultGlobalSizeLimit()),
64 ALLOW_THIS_IN_INITIALIZER_LIST(revise_allocation_factory_(this)) {
65 }
66
~WebCacheManager()67 WebCacheManager::~WebCacheManager() {
68 }
69
Add(int renderer_id)70 void WebCacheManager::Add(int renderer_id) {
71 DCHECK(inactive_renderers_.count(renderer_id) == 0);
72
73 // It is tempting to make the following DCHECK here, but it fails when a new
74 // tab is created as we observe activity from that tab because the
75 // RenderProcessHost is recreated and adds itself.
76 //
77 // DCHECK(active_renderers_.count(renderer_id) == 0);
78 //
79 // However, there doesn't seem to be much harm in receiving the calls in this
80 // order.
81
82 active_renderers_.insert(renderer_id);
83
84 RendererInfo* stats = &(stats_[renderer_id]);
85 memset(stats, 0, sizeof(*stats));
86 stats->access = Time::Now();
87
88 // Revise our allocation strategy to account for this new renderer.
89 ReviseAllocationStrategyLater();
90 }
91
Remove(int renderer_id)92 void WebCacheManager::Remove(int renderer_id) {
93 // Erase all knowledge of this renderer
94 active_renderers_.erase(renderer_id);
95 inactive_renderers_.erase(renderer_id);
96 stats_.erase(renderer_id);
97
98 // Reallocate the resources used by this renderer
99 ReviseAllocationStrategyLater();
100 }
101
ObserveActivity(int renderer_id)102 void WebCacheManager::ObserveActivity(int renderer_id) {
103 StatsMap::iterator item = stats_.find(renderer_id);
104 if (item == stats_.end())
105 return; // We might see stats for a renderer that has been destroyed.
106
107 // Record activity.
108 active_renderers_.insert(renderer_id);
109 item->second.access = Time::Now();
110
111 std::set<int>::iterator elmt = inactive_renderers_.find(renderer_id);
112 if (elmt != inactive_renderers_.end()) {
113 inactive_renderers_.erase(elmt);
114
115 // A renderer that was inactive, just became active. We should make sure
116 // it is given a fair cache allocation, but we defer this for a bit in
117 // order to make this function call cheap.
118 ReviseAllocationStrategyLater();
119 }
120 }
121
ObserveStats(int renderer_id,const WebCache::UsageStats & stats)122 void WebCacheManager::ObserveStats(int renderer_id,
123 const WebCache::UsageStats& stats) {
124 StatsMap::iterator entry = stats_.find(renderer_id);
125 if (entry == stats_.end())
126 return; // We might see stats for a renderer that has been destroyed.
127
128 // Record the updated stats.
129 entry->second.capacity = stats.capacity;
130 entry->second.deadSize = stats.deadSize;
131 entry->second.liveSize = stats.liveSize;
132 entry->second.maxDeadCapacity = stats.maxDeadCapacity;
133 entry->second.minDeadCapacity = stats.minDeadCapacity;
134
135 // trigger notification
136 WebCache::UsageStats stats_details(stats);
137 // &stats_details is only valid during the notification.
138 // See notification_types.h.
139 NotificationService::current()->Notify(
140 NotificationType::WEB_CACHE_STATS_OBSERVED,
141 Source<RenderProcessHost>(RenderProcessHost::FromID(renderer_id)),
142 Details<WebCache::UsageStats>(&stats_details));
143 }
144
SetGlobalSizeLimit(size_t bytes)145 void WebCacheManager::SetGlobalSizeLimit(size_t bytes) {
146 global_size_limit_ = bytes;
147 ReviseAllocationStrategyLater();
148 }
149
ClearCache()150 void WebCacheManager::ClearCache() {
151 // Tell each renderer process to clear the cache.
152 ClearRendederCache(active_renderers_);
153 ClearRendederCache(inactive_renderers_);
154 }
155
156 // static
GetDefaultGlobalSizeLimit()157 size_t WebCacheManager::GetDefaultGlobalSizeLimit() {
158 PrefService* perf_service = g_browser_process->local_state();
159 if (perf_service)
160 return perf_service->GetInteger(prefs::kMemoryCacheSize);
161
162 return GetDefaultCacheSize();
163 }
164
GatherStats(const std::set<int> & renderers,WebCache::UsageStats * stats)165 void WebCacheManager::GatherStats(const std::set<int>& renderers,
166 WebCache::UsageStats* stats) {
167 DCHECK(stats);
168
169 memset(stats, 0, sizeof(WebCache::UsageStats));
170
171 std::set<int>::const_iterator iter = renderers.begin();
172 while (iter != renderers.end()) {
173 StatsMap::iterator elmt = stats_.find(*iter);
174 if (elmt != stats_.end()) {
175 stats->minDeadCapacity += elmt->second.minDeadCapacity;
176 stats->maxDeadCapacity += elmt->second.maxDeadCapacity;
177 stats->capacity += elmt->second.capacity;
178 stats->liveSize += elmt->second.liveSize;
179 stats->deadSize += elmt->second.deadSize;
180 }
181 ++iter;
182 }
183 }
184
185 // static
GetSize(AllocationTactic tactic,const WebCache::UsageStats & stats)186 size_t WebCacheManager::GetSize(AllocationTactic tactic,
187 const WebCache::UsageStats& stats) {
188 switch (tactic) {
189 case DIVIDE_EVENLY:
190 // We aren't going to reserve any space for existing objects.
191 return 0;
192 case KEEP_CURRENT_WITH_HEADROOM:
193 // We need enough space for our current objects, plus some headroom.
194 return 3 * GetSize(KEEP_CURRENT, stats) / 2;
195 case KEEP_CURRENT:
196 // We need enough space to keep our current objects.
197 return stats.liveSize + stats.deadSize;
198 case KEEP_LIVE_WITH_HEADROOM:
199 // We need enough space to keep out live resources, plus some headroom.
200 return 3 * GetSize(KEEP_LIVE, stats) / 2;
201 case KEEP_LIVE:
202 // We need enough space to keep our live resources.
203 return stats.liveSize;
204 default:
205 NOTREACHED() << "Unknown cache allocation tactic";
206 return 0;
207 }
208 }
209
AttemptTactic(AllocationTactic active_tactic,const WebCache::UsageStats & active_stats,AllocationTactic inactive_tactic,const WebCache::UsageStats & inactive_stats,AllocationStrategy * strategy)210 bool WebCacheManager::AttemptTactic(
211 AllocationTactic active_tactic,
212 const WebCache::UsageStats& active_stats,
213 AllocationTactic inactive_tactic,
214 const WebCache::UsageStats& inactive_stats,
215 AllocationStrategy* strategy) {
216 DCHECK(strategy);
217
218 size_t active_size = GetSize(active_tactic, active_stats);
219 size_t inactive_size = GetSize(inactive_tactic, inactive_stats);
220
221 // Give up if we don't have enough space to use this tactic.
222 if (global_size_limit_ < active_size + inactive_size)
223 return false;
224
225 // Compute the unreserved space available.
226 size_t total_extra = global_size_limit_ - (active_size + inactive_size);
227
228 // The plan for the extra space is to divide it evenly amoung the active
229 // renderers.
230 size_t shares = active_renderers_.size();
231
232 // The inactive renderers get one share of the extra memory to be divided
233 // among themselves.
234 size_t inactive_extra = 0;
235 if (!inactive_renderers_.empty()) {
236 ++shares;
237 inactive_extra = total_extra / shares;
238 }
239
240 // The remaining memory is allocated to the active renderers.
241 size_t active_extra = total_extra - inactive_extra;
242
243 // Actually compute the allocations for each renderer.
244 AddToStrategy(active_renderers_, active_tactic, active_extra, strategy);
245 AddToStrategy(inactive_renderers_, inactive_tactic, inactive_extra, strategy);
246
247 // We succeeded in computing an allocation strategy.
248 return true;
249 }
250
AddToStrategy(const std::set<int> & renderers,AllocationTactic tactic,size_t extra_bytes_to_allocate,AllocationStrategy * strategy)251 void WebCacheManager::AddToStrategy(const std::set<int>& renderers,
252 AllocationTactic tactic,
253 size_t extra_bytes_to_allocate,
254 AllocationStrategy* strategy) {
255 DCHECK(strategy);
256
257 // Nothing to do if there are no renderers. It is common for there to be no
258 // inactive renderers if there is a single active tab.
259 if (renderers.empty())
260 return;
261
262 // Divide the extra memory evenly among the renderers.
263 size_t extra_each = extra_bytes_to_allocate / renderers.size();
264
265 std::set<int>::const_iterator iter = renderers.begin();
266 while (iter != renderers.end()) {
267 size_t cache_size = extra_each;
268
269 // Add in the space required to implement |tactic|.
270 StatsMap::iterator elmt = stats_.find(*iter);
271 if (elmt != stats_.end())
272 cache_size += GetSize(tactic, elmt->second);
273
274 // Record the allocation in our strategy.
275 strategy->push_back(Allocation(*iter, cache_size));
276 ++iter;
277 }
278 }
279
EnactStrategy(const AllocationStrategy & strategy)280 void WebCacheManager::EnactStrategy(const AllocationStrategy& strategy) {
281 // Inform each render process of its cache allocation.
282 AllocationStrategy::const_iterator allocation = strategy.begin();
283 while (allocation != strategy.end()) {
284 RenderProcessHost* host = RenderProcessHost::FromID(allocation->first);
285 if (host) {
286 // This is the capacity this renderer has been allocated.
287 size_t capacity = allocation->second;
288
289 // We don't reserve any space for dead objects in the cache. Instead, we
290 // prefer to keep live objects around. There is probably some performance
291 // tuning to be done here.
292 size_t min_dead_capacity = 0;
293
294 // We allow the dead objects to consume all of the cache, if the renderer
295 // so desires. If we wanted this memory, we would have set the total
296 // capacity lower.
297 size_t max_dead_capacity = capacity;
298
299 host->Send(new ViewMsg_SetCacheCapacities(min_dead_capacity,
300 max_dead_capacity,
301 capacity));
302 }
303 ++allocation;
304 }
305 }
306
ClearRendederCache(const std::set<int> & renderers)307 void WebCacheManager::ClearRendederCache(const std::set<int>& renderers) {
308 std::set<int>::const_iterator iter = renderers.begin();
309 for (; iter != renderers.end(); ++iter) {
310 RenderProcessHost* host = RenderProcessHost::FromID(*iter);
311 if (host)
312 host->Send(new ViewMsg_ClearCache());
313 }
314 }
315
ReviseAllocationStrategy()316 void WebCacheManager::ReviseAllocationStrategy() {
317 DCHECK(stats_.size() <=
318 active_renderers_.size() + inactive_renderers_.size());
319
320 // Check if renderers have gone inactive.
321 FindInactiveRenderers();
322
323 // Gather statistics
324 WebCache::UsageStats active;
325 WebCache::UsageStats inactive;
326 GatherStats(active_renderers_, &active);
327 GatherStats(inactive_renderers_, &inactive);
328
329 UMA_HISTOGRAM_COUNTS_100("Cache.ActiveTabs", active_renderers_.size());
330 UMA_HISTOGRAM_COUNTS_100("Cache.InactiveTabs", inactive_renderers_.size());
331 UMA_HISTOGRAM_MEMORY_MB("Cache.ActiveCapacityMB",
332 active.capacity / 1024 / 1024);
333 UMA_HISTOGRAM_MEMORY_MB("Cache.ActiveDeadSizeMB",
334 active.deadSize / 1024 / 1024);
335 UMA_HISTOGRAM_MEMORY_MB("Cache.ActiveLiveSizeMB",
336 active.liveSize / 1024 / 1024);
337 UMA_HISTOGRAM_MEMORY_MB("Cache.InactiveCapacityMB",
338 inactive.capacity / 1024 / 1024);
339 UMA_HISTOGRAM_MEMORY_MB("Cache.InactiveDeadSizeMB",
340 inactive.deadSize / 1024 / 1024);
341 UMA_HISTOGRAM_MEMORY_MB("Cache.InactiveLiveSizeMB",
342 inactive.liveSize / 1024 / 1024);
343
344 // Compute an allocation strategy.
345 //
346 // We attempt various tactics in order of preference. Our first preference
347 // is not to evict any objects. If we don't have enough resources, we'll
348 // first try to evict dead data only. If that fails, we'll just divide the
349 // resources we have evenly.
350 //
351 // We always try to give the active renderers some head room in their
352 // allocations so they can take memory away from an inactive renderer with
353 // a large cache allocation.
354 //
355 // Notice the early exit will prevent attempting less desirable tactics once
356 // we've found a workable strategy.
357 AllocationStrategy strategy;
358 if ( // Ideally, we'd like to give the active renderers some headroom and
359 // keep all our current objects.
360 AttemptTactic(KEEP_CURRENT_WITH_HEADROOM, active,
361 KEEP_CURRENT, inactive, &strategy) ||
362 // If we can't have that, then we first try to evict the dead objects in
363 // the caches of inactive renderers.
364 AttemptTactic(KEEP_CURRENT_WITH_HEADROOM, active,
365 KEEP_LIVE, inactive, &strategy) ||
366 // Next, we try to keep the live objects in the active renders (with some
367 // room for new objects) and give whatever is left to the inactive
368 // renderers.
369 AttemptTactic(KEEP_LIVE_WITH_HEADROOM, active,
370 DIVIDE_EVENLY, inactive, &strategy) ||
371 // If we've gotten this far, then we are very tight on memory. Let's try
372 // to at least keep around the live objects for the active renderers.
373 AttemptTactic(KEEP_LIVE, active, DIVIDE_EVENLY, inactive, &strategy) ||
374 // We're basically out of memory. The best we can do is just divide up
375 // what we have and soldier on.
376 AttemptTactic(DIVIDE_EVENLY, active, DIVIDE_EVENLY, inactive,
377 &strategy)) {
378 // Having found a workable strategy, we enact it.
379 EnactStrategy(strategy);
380 } else {
381 // DIVIDE_EVENLY / DIVIDE_EVENLY should always succeed.
382 NOTREACHED() << "Unable to find a cache allocation";
383 }
384 }
385
ReviseAllocationStrategyLater()386 void WebCacheManager::ReviseAllocationStrategyLater() {
387 // Ask to be called back in a few milliseconds to actually recompute our
388 // allocation.
389 MessageLoop::current()->PostDelayedTask(FROM_HERE,
390 revise_allocation_factory_.NewRunnableMethod(
391 &WebCacheManager::ReviseAllocationStrategy),
392 kReviseAllocationDelayMS);
393 }
394
FindInactiveRenderers()395 void WebCacheManager::FindInactiveRenderers() {
396 std::set<int>::const_iterator iter = active_renderers_.begin();
397 while (iter != active_renderers_.end()) {
398 StatsMap::iterator elmt = stats_.find(*iter);
399 DCHECK(elmt != stats_.end());
400 TimeDelta idle = Time::Now() - elmt->second.access;
401 if (idle >= TimeDelta::FromMinutes(kRendererInactiveThresholdMinutes)) {
402 // Moved to inactive status. This invalidates our iterator.
403 inactive_renderers_.insert(*iter);
404 active_renderers_.erase(*iter);
405 iter = active_renderers_.begin();
406 continue;
407 }
408 ++iter;
409 }
410 }
411