chrome/browser/renderer_host/web_cache_manager.cc

   1 // Copyright (c) 2012 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/bind.h"
  10 #include "base/compiler_specific.h"
  11 #include "base/memory/singleton.h"
  12 #include "base/message_loop/message_loop.h"
  13 #include "base/metrics/histogram.h"
  14 #include "base/prefs/pref_registry_simple.h"
  15 #include "base/prefs/pref_service.h"
  16 #include "base/sys_info.h"
  17 #include "base/time/time.h"
  18 #include "chrome/browser/browser_process.h"
  19 #include "chrome/browser/chrome_notification_types.h"
  20 #include "chrome/common/chrome_constants.h"
  21 #include "chrome/common/pref_names.h"
  22 #include "chrome/common/render_messages.h"
  23 #include "content/public/browser/notification_service.h"
  24 #include "content/public/browser/render_process_host.h"
  25
  26 using base::Time;
  27 using base::TimeDelta;
  28 using blink::WebCache;
  29
  30 static const int kReviseAllocationDelayMS = 200;
  31
  32 // The default size limit of the in-memory cache is 8 MB
  33 static const int kDefaultMemoryCacheSize = 8 * 1024 * 1024;
  34
  35 namespace {
  36
  37 int GetDefaultCacheSize() {
  38   // Start off with a modest default
  39   int default_cache_size = kDefaultMemoryCacheSize;
  40
  41   // Check how much physical memory the OS has
  42   int mem_size_mb = base::SysInfo::AmountOfPhysicalMemoryMB();
  43   if (mem_size_mb >= 1000)  // If we have a GB of memory, set a larger default.
  44     default_cache_size *= 4;
  45   else if (mem_size_mb >= 512)  // With 512 MB, set a slightly larger default.
  46     default_cache_size *= 2;
  47
  48   UMA_HISTOGRAM_MEMORY_MB("Cache.MaxCacheSizeMB",
  49                           default_cache_size / 1024 / 1024);
  50
  51   return default_cache_size;
  52 }
  53
  54 }  // anonymous namespace
  55
  56 // static
  57 void WebCacheManager::RegisterPrefs(PrefRegistrySimple* registry) {
  58   registry->RegisterIntegerPref(prefs::kMemoryCacheSize, GetDefaultCacheSize());
  59 }
  60
  61 // static
  62 WebCacheManager* WebCacheManager::GetInstance() {
  63   return Singleton<WebCacheManager>::get();
  64 }
  65
  66 WebCacheManager::WebCacheManager()
  67     : global_size_limit_(GetDefaultGlobalSizeLimit()),
  68       weak_factory_(this) {
  69   registrar_.Add(this, content::NOTIFICATION_RENDERER_PROCESS_CREATED,
  70                  content::NotificationService::AllBrowserContextsAndSources());
  71   registrar_.Add(this, content::NOTIFICATION_RENDERER_PROCESS_TERMINATED,
  72                  content::NotificationService::AllBrowserContextsAndSources());
  73 }
  74
  75 WebCacheManager::~WebCacheManager() {
  76 }
  77
  78 void WebCacheManager::Add(int renderer_id) {
  79   DCHECK(inactive_renderers_.count(renderer_id) == 0);
  80
  81   // It is tempting to make the following DCHECK here, but it fails when a new
  82   // tab is created as we observe activity from that tab because the
  83   // RenderProcessHost is recreated and adds itself.
  84   //
  85   //   DCHECK(active_renderers_.count(renderer_id) == 0);
  86   //
  87   // However, there doesn't seem to be much harm in receiving the calls in this
  88   // order.
  89
  90   active_renderers_.insert(renderer_id);
  91
  92   RendererInfo* stats = &(stats_[renderer_id]);
  93   memset(stats, 0, sizeof(*stats));
  94   stats->access = Time::Now();
  95
  96   // Revise our allocation strategy to account for this new renderer.
  97   ReviseAllocationStrategyLater();
  98 }
  99
 100 void WebCacheManager::Remove(int renderer_id) {
 101   // Erase all knowledge of this renderer
 102   active_renderers_.erase(renderer_id);
 103   inactive_renderers_.erase(renderer_id);
 104   stats_.erase(renderer_id);
 105
 106   // Reallocate the resources used by this renderer
 107   ReviseAllocationStrategyLater();
 108 }
 109
 110 void WebCacheManager::ObserveActivity(int renderer_id) {
 111   StatsMap::iterator item = stats_.find(renderer_id);
 112   if (item == stats_.end())
 113     return;  // We might see stats for a renderer that has been destroyed.
 114
 115   // Record activity.
 116   active_renderers_.insert(renderer_id);
 117   item->second.access = Time::Now();
 118
 119   std::set<int>::iterator elmt = inactive_renderers_.find(renderer_id);
 120   if (elmt != inactive_renderers_.end()) {
 121     inactive_renderers_.erase(elmt);
 122
 123     // A renderer that was inactive, just became active.  We should make sure
 124     // it is given a fair cache allocation, but we defer this for a bit in
 125     // order to make this function call cheap.
 126     ReviseAllocationStrategyLater();
 127   }
 128 }
 129
 130 void WebCacheManager::ObserveStats(int renderer_id,
 131                                    const WebCache::UsageStats& stats) {
 132   StatsMap::iterator entry = stats_.find(renderer_id);
 133   if (entry == stats_.end())
 134     return;  // We might see stats for a renderer that has been destroyed.
 135
 136   // Record the updated stats.
 137   entry->second.capacity = stats.capacity;
 138   entry->second.deadSize = stats.deadSize;
 139   entry->second.liveSize = stats.liveSize;
 140   entry->second.maxDeadCapacity = stats.maxDeadCapacity;
 141   entry->second.minDeadCapacity = stats.minDeadCapacity;
 142 }
 143
 144 void WebCacheManager::SetGlobalSizeLimit(size_t bytes) {
 145   global_size_limit_ = bytes;
 146   ReviseAllocationStrategyLater();
 147 }
 148
 149 void WebCacheManager::ClearCache() {
 150   // Tell each renderer process to clear the cache.
 151   ClearRendererCache(active_renderers_, INSTANTLY);
 152   ClearRendererCache(inactive_renderers_, INSTANTLY);
 153 }
 154
 155 void WebCacheManager::ClearCacheOnNavigation() {
 156   // Tell each renderer process to clear the cache when a tab is reloaded or
 157   // the user navigates to a new website.
 158   ClearRendererCache(active_renderers_, ON_NAVIGATION);
 159   ClearRendererCache(inactive_renderers_, ON_NAVIGATION);
 160 }
 161
 162 void WebCacheManager::Observe(int type,
 163                               const content::NotificationSource& source,
 164                               const content::NotificationDetails& details) {
 165   switch (type) {
 166     case content::NOTIFICATION_RENDERER_PROCESS_CREATED: {
 167       content::RenderProcessHost* process =
 168           content::Source<content::RenderProcessHost>(source).ptr();
 169       Add(process->GetID());
 170       break;
 171     }
 172     case content::NOTIFICATION_RENDERER_PROCESS_TERMINATED: {
 173       content::RenderProcessHost* process =
 174           content::Source<content::RenderProcessHost>(source).ptr();
 175       Remove(process->GetID());
 176       break;
 177     }
 178     default:
 179       NOTREACHED();
 180       break;
 181   }
 182 }
 183
 184 // static
 185 size_t WebCacheManager::GetDefaultGlobalSizeLimit() {
 186   PrefService* perf_service = g_browser_process->local_state();
 187   if (perf_service)
 188     return perf_service->GetInteger(prefs::kMemoryCacheSize);
 189
 190   return GetDefaultCacheSize();
 191 }
 192
 193 void WebCacheManager::GatherStats(const std::set<int>& renderers,
 194                                   WebCache::UsageStats* stats) {
 195   DCHECK(stats);
 196
 197   memset(stats, 0, sizeof(WebCache::UsageStats));
 198
 199   std::set<int>::const_iterator iter = renderers.begin();
 200   while (iter != renderers.end()) {
 201     StatsMap::iterator elmt = stats_.find(*iter);
 202     if (elmt != stats_.end()) {
 203       stats->minDeadCapacity += elmt->second.minDeadCapacity;
 204       stats->maxDeadCapacity += elmt->second.maxDeadCapacity;
 205       stats->capacity += elmt->second.capacity;
 206       stats->liveSize += elmt->second.liveSize;
 207       stats->deadSize += elmt->second.deadSize;
 208     }
 209     ++iter;
 210   }
 211 }
 212
 213 // static
 214 size_t WebCacheManager::GetSize(AllocationTactic tactic,
 215                                 const WebCache::UsageStats& stats) {
 216   switch (tactic) {
 217   case DIVIDE_EVENLY:
 218     // We aren't going to reserve any space for existing objects.
 219     return 0;
 220   case KEEP_CURRENT_WITH_HEADROOM:
 221     // We need enough space for our current objects, plus some headroom.
 222     return 3 * GetSize(KEEP_CURRENT, stats) / 2;
 223   case KEEP_CURRENT:
 224     // We need enough space to keep our current objects.
 225     return stats.liveSize + stats.deadSize;
 226   case KEEP_LIVE_WITH_HEADROOM:
 227     // We need enough space to keep out live resources, plus some headroom.
 228     return 3 * GetSize(KEEP_LIVE, stats) / 2;
 229   case KEEP_LIVE:
 230     // We need enough space to keep our live resources.
 231     return stats.liveSize;
 232   default:
 233     NOTREACHED() << "Unknown cache allocation tactic";
 234     return 0;
 235   }
 236 }
 237
 238 bool WebCacheManager::AttemptTactic(
 239     AllocationTactic active_tactic,
 240     const WebCache::UsageStats& active_stats,
 241     AllocationTactic inactive_tactic,
 242     const WebCache::UsageStats& inactive_stats,
 243     AllocationStrategy* strategy) {
 244   DCHECK(strategy);
 245
 246   size_t active_size = GetSize(active_tactic, active_stats);
 247   size_t inactive_size = GetSize(inactive_tactic, inactive_stats);
 248
 249   // Give up if we don't have enough space to use this tactic.
 250   if (global_size_limit_ < active_size + inactive_size)
 251     return false;
 252
 253   // Compute the unreserved space available.
 254   size_t total_extra = global_size_limit_ - (active_size + inactive_size);
 255
 256   // The plan for the extra space is to divide it evenly amoung the active
 257   // renderers.
 258   size_t shares = active_renderers_.size();
 259
 260   // The inactive renderers get one share of the extra memory to be divided
 261   // among themselves.
 262   size_t inactive_extra = 0;
 263   if (!inactive_renderers_.empty()) {
 264     ++shares;
 265     inactive_extra = total_extra / shares;
 266   }
 267
 268   // The remaining memory is allocated to the active renderers.
 269   size_t active_extra = total_extra - inactive_extra;
 270
 271   // Actually compute the allocations for each renderer.
 272   AddToStrategy(active_renderers_, active_tactic, active_extra, strategy);
 273   AddToStrategy(inactive_renderers_, inactive_tactic, inactive_extra, strategy);
 274
 275   // We succeeded in computing an allocation strategy.
 276   return true;
 277 }
 278
 279 void WebCacheManager::AddToStrategy(const std::set<int>& renderers,
 280                                     AllocationTactic tactic,
 281                                     size_t extra_bytes_to_allocate,
 282                                     AllocationStrategy* strategy) {
 283   DCHECK(strategy);
 284
 285   // Nothing to do if there are no renderers.  It is common for there to be no
 286   // inactive renderers if there is a single active tab.
 287   if (renderers.empty())
 288     return;
 289
 290   // Divide the extra memory evenly among the renderers.
 291   size_t extra_each = extra_bytes_to_allocate / renderers.size();
 292
 293   std::set<int>::const_iterator iter = renderers.begin();
 294   while (iter != renderers.end()) {
 295     size_t cache_size = extra_each;
 296
 297     // Add in the space required to implement |tactic|.
 298     StatsMap::iterator elmt = stats_.find(*iter);
 299     if (elmt != stats_.end())
 300       cache_size += GetSize(tactic, elmt->second);
 301
 302     // Record the allocation in our strategy.
 303     strategy->push_back(Allocation(*iter, cache_size));
 304     ++iter;
 305   }
 306 }
 307
 308 void WebCacheManager::EnactStrategy(const AllocationStrategy& strategy) {
 309   // Inform each render process of its cache allocation.
 310   AllocationStrategy::const_iterator allocation = strategy.begin();
 311   while (allocation != strategy.end()) {
 312     content::RenderProcessHost* host =
 313         content::RenderProcessHost::FromID(allocation->first);
 314     if (host) {
 315       // This is the capacity this renderer has been allocated.
 316       size_t capacity = allocation->second;
 317
 318       // We don't reserve any space for dead objects in the cache. Instead, we
 319       // prefer to keep live objects around. There is probably some performance
 320       // tuning to be done here.
 321       size_t min_dead_capacity = 0;
 322
 323       // We allow the dead objects to consume up to half of the cache capacity.
 324       size_t max_dead_capacity = capacity / 2;
 325       if (base::SysInfo::IsLowEndDevice()) {
 326         max_dead_capacity = std::min(static_cast<size_t>(512 * 1024),
 327                                      max_dead_capacity);
 328       }
 329       host->Send(new ChromeViewMsg_SetCacheCapacities(min_dead_capacity,
 330                                                       max_dead_capacity,
 331                                                       capacity));
 332     }
 333     ++allocation;
 334   }
 335 }
 336
 337 void WebCacheManager::ClearRendererCache(
 338     const std::set<int>& renderers,
 339     WebCacheManager::ClearCacheOccasion occasion) {
 340   std::set<int>::const_iterator iter = renderers.begin();
 341   for (; iter != renderers.end(); ++iter) {
 342     content::RenderProcessHost* host =
 343         content::RenderProcessHost::FromID(*iter);
 344     if (host)
 345       host->Send(new ChromeViewMsg_ClearCache(occasion == ON_NAVIGATION));
 346   }
 347 }
 348
 349 void WebCacheManager::ReviseAllocationStrategy() {
 350   DCHECK(stats_.size() <=
 351       active_renderers_.size() + inactive_renderers_.size());
 352
 353   // Check if renderers have gone inactive.
 354   FindInactiveRenderers();
 355
 356   // Gather statistics
 357   WebCache::UsageStats active;
 358   WebCache::UsageStats inactive;
 359   GatherStats(active_renderers_, &active);
 360   GatherStats(inactive_renderers_, &inactive);
 361
 362   UMA_HISTOGRAM_COUNTS_100("Cache.ActiveTabs", active_renderers_.size());
 363   UMA_HISTOGRAM_COUNTS_100("Cache.InactiveTabs", inactive_renderers_.size());
 364   UMA_HISTOGRAM_MEMORY_MB("Cache.ActiveCapacityMB",
 365                           active.capacity / 1024 / 1024);
 366   UMA_HISTOGRAM_MEMORY_MB("Cache.ActiveDeadSizeMB",
 367                           active.deadSize / 1024 / 1024);
 368   UMA_HISTOGRAM_MEMORY_MB("Cache.ActiveLiveSizeMB",
 369                           active.liveSize / 1024 / 1024);
 370   UMA_HISTOGRAM_MEMORY_MB("Cache.InactiveCapacityMB",
 371                           inactive.capacity / 1024 / 1024);
 372   UMA_HISTOGRAM_MEMORY_MB("Cache.InactiveDeadSizeMB",
 373                           inactive.deadSize / 1024 / 1024);
 374   UMA_HISTOGRAM_MEMORY_MB("Cache.InactiveLiveSizeMB",
 375                           inactive.liveSize / 1024 / 1024);
 376
 377   // Compute an allocation strategy.
 378   //
 379   // We attempt various tactics in order of preference.  Our first preference
 380   // is not to evict any objects.  If we don't have enough resources, we'll
 381   // first try to evict dead data only.  If that fails, we'll just divide the
 382   // resources we have evenly.
 383   //
 384   // We always try to give the active renderers some head room in their
 385   // allocations so they can take memory away from an inactive renderer with
 386   // a large cache allocation.
 387   //
 388   // Notice the early exit will prevent attempting less desirable tactics once
 389   // we've found a workable strategy.
 390   AllocationStrategy strategy;
 391   if (  // Ideally, we'd like to give the active renderers some headroom and
 392         // keep all our current objects.
 393       AttemptTactic(KEEP_CURRENT_WITH_HEADROOM, active,
 394                     KEEP_CURRENT, inactive, &strategy) ||
 395       // If we can't have that, then we first try to evict the dead objects in
 396       // the caches of inactive renderers.
 397       AttemptTactic(KEEP_CURRENT_WITH_HEADROOM, active,
 398                     KEEP_LIVE, inactive, &strategy) ||
 399       // Next, we try to keep the live objects in the active renders (with some
 400       // room for new objects) and give whatever is left to the inactive
 401       // renderers.
 402       AttemptTactic(KEEP_LIVE_WITH_HEADROOM, active,
 403                     DIVIDE_EVENLY, inactive, &strategy) ||
 404       // If we've gotten this far, then we are very tight on memory.  Let's try
 405       // to at least keep around the live objects for the active renderers.
 406       AttemptTactic(KEEP_LIVE, active, DIVIDE_EVENLY, inactive, &strategy) ||
 407       // We're basically out of memory.  The best we can do is just divide up
 408       // what we have and soldier on.
 409       AttemptTactic(DIVIDE_EVENLY, active, DIVIDE_EVENLY, inactive,
 410                     &strategy)) {
 411     // Having found a workable strategy, we enact it.
 412     EnactStrategy(strategy);
 413   } else {
 414     // DIVIDE_EVENLY / DIVIDE_EVENLY should always succeed.
 415     NOTREACHED() << "Unable to find a cache allocation";
 416   }
 417 }
 418
 419 void WebCacheManager::ReviseAllocationStrategyLater() {
 420   // Ask to be called back in a few milliseconds to actually recompute our
 421   // allocation.
 422   base::MessageLoop::current()->PostDelayedTask(FROM_HERE,
 423       base::Bind(
 424           &WebCacheManager::ReviseAllocationStrategy,
 425           weak_factory_.GetWeakPtr()),
 426       base::TimeDelta::FromMilliseconds(kReviseAllocationDelayMS));
 427 }
 428
 429 void WebCacheManager::FindInactiveRenderers() {
 430   std::set<int>::const_iterator iter = active_renderers_.begin();
 431   while (iter != active_renderers_.end()) {
 432     StatsMap::iterator elmt = stats_.find(*iter);
 433     DCHECK(elmt != stats_.end());
 434     TimeDelta idle = Time::Now() - elmt->second.access;
 435     if (idle >= TimeDelta::FromMinutes(kRendererInactiveThresholdMinutes)) {
 436       // Moved to inactive status.  This invalidates our iterator.
 437       inactive_renderers_.insert(*iter);
 438       active_renderers_.erase(*iter);
 439       iter = active_renderers_.begin();
 440       continue;
 441     }
 442     ++iter;
 443   }
 444 }