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