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