content/browser/loader/resource_scheduler.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 <set>
   6
   7 #include "content/browser/loader/resource_scheduler.h"
   8
   9 #include "base/stl_util.h"
  10 #include "content/common/resource_messages.h"
  11 #include "content/browser/loader/resource_message_delegate.h"
  12 #include "content/public/browser/resource_controller.h"
  13 #include "content/public/browser/resource_request_info.h"
  14 #include "content/public/browser/resource_throttle.h"
  15 #include "ipc/ipc_message_macros.h"
  16 #include "net/base/host_port_pair.h"
  17 #include "net/base/load_flags.h"
  18 #include "net/base/request_priority.h"
  19 #include "net/http/http_server_properties.h"
  20 #include "net/url_request/url_request.h"
  21 #include "net/url_request/url_request_context.h"
  22
  23 namespace content {
  24
  25 static const size_t kMaxNumDelayableRequestsPerClient = 10;
  26 static const size_t kMaxNumDelayableRequestsPerHost = 6;
  27
  28
  29 struct ResourceScheduler::RequestPriorityParams {
  30   RequestPriorityParams()
  31     : priority(net::DEFAULT_PRIORITY),
  32       intra_priority(0) {
  33   }
  34
  35   RequestPriorityParams(net::RequestPriority priority, int intra_priority)
  36     : priority(priority),
  37       intra_priority(intra_priority) {
  38   }
  39
  40   bool operator==(const RequestPriorityParams& other) const {
  41     return (priority == other.priority) &&
  42         (intra_priority == other.intra_priority);
  43   }
  44
  45   bool operator!=(const RequestPriorityParams& other) const {
  46     return !(*this == other);
  47   }
  48
  49   bool GreaterThan(const RequestPriorityParams& other) const {
  50     if (priority != other.priority)
  51       return priority > other.priority;
  52     return intra_priority > other.intra_priority;
  53   }
  54
  55   net::RequestPriority priority;
  56   int intra_priority;
  57 };
  58
  59 class ResourceScheduler::RequestQueue {
  60  public:
  61   typedef std::multiset<ScheduledResourceRequest*, ScheduledResourceSorter>
  62       NetQueue;
  63
  64   RequestQueue() : fifo_ordering_ids_(0) {}
  65   ~RequestQueue() {}
  66
  67   // Adds |request| to the queue with given |priority|.
  68   void Insert(ScheduledResourceRequest* request);
  69
  70   // Removes |request| from the queue.
  71   void Erase(ScheduledResourceRequest* request) {
  72     PointerMap::iterator it = pointers_.find(request);
  73     DCHECK(it != pointers_.end());
  74     if (it == pointers_.end())
  75       return;
  76     queue_.erase(it->second);
  77     pointers_.erase(it);
  78   }
  79
  80   NetQueue::iterator GetNextHighestIterator() {
  81     return queue_.begin();
  82   }
  83
  84   NetQueue::iterator End() {
  85     return queue_.end();
  86   }
  87
  88   // Returns true if |request| is queued.
  89   bool IsQueued(ScheduledResourceRequest* request) const {
  90     return ContainsKey(pointers_, request);
  91   }
  92
  93   // Returns true if no requests are queued.
  94   bool IsEmpty() const { return queue_.size() == 0; }
  95
  96  private:
  97   typedef std::map<ScheduledResourceRequest*, NetQueue::iterator> PointerMap;
  98
  99   uint32 MakeFifoOrderingId() {
 100     fifo_ordering_ids_ += 1;
 101     return fifo_ordering_ids_;
 102   }
 103
 104   // Used to create an ordering ID for scheduled resources so that resources
 105   // with same priority/intra_priority stay in fifo order.
 106   uint32 fifo_ordering_ids_;
 107
 108   NetQueue queue_;
 109   PointerMap pointers_;
 110 };
 111
 112 // This is the handle we return to the ResourceDispatcherHostImpl so it can
 113 // interact with the request.
 114 class ResourceScheduler::ScheduledResourceRequest
 115     : public ResourceMessageDelegate,
 116       public ResourceThrottle {
 117  public:
 118   ScheduledResourceRequest(const ClientId& client_id,
 119                            net::URLRequest* request,
 120                            ResourceScheduler* scheduler,
 121                            const RequestPriorityParams& priority)
 122       : ResourceMessageDelegate(request),
 123         client_id_(client_id),
 124         request_(request),
 125         ready_(false),
 126         deferred_(false),
 127         scheduler_(scheduler),
 128         priority_(priority),
 129         fifo_ordering_(0),
 130         accounted_as_delayable_request_(false) {
 131     TRACE_EVENT_ASYNC_BEGIN1("net", "URLRequest", request_,
 132                              "url", request->url().spec());
 133   }
 134
 135   virtual ~ScheduledResourceRequest() {
 136     scheduler_->RemoveRequest(this);
 137   }
 138
 139   void Start() {
 140     TRACE_EVENT_ASYNC_STEP_PAST0("net", "URLRequest", request_, "Queued");
 141     ready_ = true;
 142     if (deferred_ && request_->status().is_success()) {
 143       deferred_ = false;
 144       controller()->Resume();
 145     }
 146   }
 147
 148   void set_request_priority_params(const RequestPriorityParams& priority) {
 149     priority_ = priority;
 150   }
 151   const RequestPriorityParams& get_request_priority_params() const {
 152     return priority_;
 153   }
 154   const ClientId& client_id() const { return client_id_; }
 155   net::URLRequest* url_request() { return request_; }
 156   const net::URLRequest* url_request() const { return request_; }
 157   uint32 fifo_ordering() const { return fifo_ordering_; }
 158   void set_fifo_ordering(uint32 fifo_ordering) {
 159     fifo_ordering_ = fifo_ordering;
 160   }
 161   bool accounted_as_delayable_request() const {
 162     return accounted_as_delayable_request_;
 163   }
 164   void set_accounted_as_delayable_request(bool accounted) {
 165     accounted_as_delayable_request_ = accounted;
 166   }
 167
 168  private:
 169   // ResourceMessageDelegate interface:
 170   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE {
 171     bool handled = true;
 172     IPC_BEGIN_MESSAGE_MAP(ScheduledResourceRequest, message)
 173       IPC_MESSAGE_HANDLER(ResourceHostMsg_DidChangePriority, DidChangePriority)
 174       IPC_MESSAGE_UNHANDLED(handled = false)
 175     IPC_END_MESSAGE_MAP()
 176     return handled;
 177   }
 178
 179   // ResourceThrottle interface:
 180   virtual void WillStartRequest(bool* defer) OVERRIDE {
 181     deferred_ = *defer = !ready_;
 182   }
 183
 184   virtual const char* GetNameForLogging() const OVERRIDE {
 185     return "ResourceScheduler";
 186   }
 187
 188   void DidChangePriority(int request_id, net::RequestPriority new_priority,
 189                          int intra_priority_value) {
 190     scheduler_->ReprioritizeRequest(this, new_priority, intra_priority_value);
 191   }
 192
 193   ClientId client_id_;
 194   net::URLRequest* request_;
 195   bool ready_;
 196   bool deferred_;
 197   ResourceScheduler* scheduler_;
 198   RequestPriorityParams priority_;
 199   uint32 fifo_ordering_;
 200   // True if the request is delayable in |in_flight_requests_|.
 201   bool accounted_as_delayable_request_;
 202
 203   DISALLOW_COPY_AND_ASSIGN(ScheduledResourceRequest);
 204 };
 205
 206 bool ResourceScheduler::ScheduledResourceSorter::operator()(
 207     const ScheduledResourceRequest* a,
 208     const ScheduledResourceRequest* b) const {
 209   // Want the set to be ordered first by decreasing priority, then by
 210   // decreasing intra_priority.
 211   // ie. with (priority, intra_priority)
 212   // [(1, 0), (1, 0), (0, 100), (0, 0)]
 213   if (a->get_request_priority_params() != b->get_request_priority_params())
 214     return a->get_request_priority_params().GreaterThan(
 215         b->get_request_priority_params());
 216
 217   // If priority/intra_priority is the same, fall back to fifo ordering.
 218   // std::multiset doesn't guarantee this until c++11.
 219   return a->fifo_ordering() < b->fifo_ordering();
 220 }
 221
 222 void ResourceScheduler::RequestQueue::Insert(
 223     ScheduledResourceRequest* request) {
 224   DCHECK(!ContainsKey(pointers_, request));
 225   request->set_fifo_ordering(MakeFifoOrderingId());
 226   pointers_[request] = queue_.insert(request);
 227 }
 228
 229 // Each client represents a tab.
 230 class ResourceScheduler::Client {
 231  public:
 232   Client()
 233       : has_body_(false),
 234         using_spdy_proxy_(false),
 235         total_delayable_count_(0) {}
 236   ~Client() {}
 237
 238   void ScheduleRequest(
 239       net::URLRequest* url_request,
 240       ScheduledResourceRequest* request) {
 241     if (ShouldStartRequest(request) == START_REQUEST) {
 242       StartRequest(request);
 243     } else {
 244       pending_requests_.Insert(request);
 245     }
 246   }
 247
 248   void RemoveRequest(ScheduledResourceRequest* request) {
 249     if (pending_requests_.IsQueued(request)) {
 250       pending_requests_.Erase(request);
 251       DCHECK(!ContainsKey(in_flight_requests_, request));
 252     } else {
 253       EraseInFlightRequest(request);
 254
 255       // Removing this request may have freed up another to load.
 256       LoadAnyStartablePendingRequests();
 257     }
 258   }
 259
 260   RequestSet RemoveAllRequests() {
 261     RequestSet unowned_requests;
 262     for (RequestSet::iterator it = in_flight_requests_.begin();
 263          it != in_flight_requests_.end(); ++it) {
 264       unowned_requests.insert(*it);
 265       (*it)->set_accounted_as_delayable_request(false);
 266     }
 267     ClearInFlightRequests();
 268     return unowned_requests;
 269   }
 270
 271   void OnNavigate() {
 272     has_body_ = false;
 273   }
 274
 275   void OnWillInsertBody() {
 276     has_body_ = true;
 277     LoadAnyStartablePendingRequests();
 278   }
 279
 280   void OnReceivedSpdyProxiedHttpResponse() {
 281     if (!using_spdy_proxy_) {
 282       using_spdy_proxy_ = true;
 283       LoadAnyStartablePendingRequests();
 284     }
 285   }
 286
 287   void ReprioritizeRequest(ScheduledResourceRequest* request,
 288                            RequestPriorityParams old_priority_params,
 289                            RequestPriorityParams new_priority_params) {
 290     request->url_request()->SetPriority(new_priority_params.priority);
 291     request->set_request_priority_params(new_priority_params);
 292     if (!pending_requests_.IsQueued(request)) {
 293       DCHECK(ContainsKey(in_flight_requests_, request));
 294       // The priority and SPDY support may have changed, so update the
 295       // delayable count.
 296       SetRequestDelayable(request, IsDelayableRequest(request));
 297       // Request has already started.
 298       return;
 299     }
 300
 301     pending_requests_.Erase(request);
 302     pending_requests_.Insert(request);
 303
 304     if (new_priority_params.priority > old_priority_params.priority) {
 305       // Check if this request is now able to load at its new priority.
 306       LoadAnyStartablePendingRequests();
 307     }
 308   }
 309
 310  private:
 311   enum ShouldStartReqResult {
 312       DO_NOT_START_REQUEST_AND_STOP_SEARCHING = -2,
 313       DO_NOT_START_REQUEST_AND_KEEP_SEARCHING = -1,
 314       START_REQUEST = 1,
 315   };
 316
 317   void InsertInFlightRequest(ScheduledResourceRequest* request) {
 318     in_flight_requests_.insert(request);
 319     if (IsDelayableRequest(request))
 320       SetRequestDelayable(request, true);
 321   }
 322
 323   void EraseInFlightRequest(ScheduledResourceRequest* request) {
 324     size_t erased = in_flight_requests_.erase(request);
 325     DCHECK_EQ(1u, erased);
 326     SetRequestDelayable(request, false);
 327     DCHECK_LE(total_delayable_count_, in_flight_requests_.size());
 328   }
 329
 330   void ClearInFlightRequests() {
 331     in_flight_requests_.clear();
 332     total_delayable_count_ = 0;
 333   }
 334
 335   bool IsDelayableRequest(ScheduledResourceRequest* request) {
 336     if (request->url_request()->priority() < net::LOW) {
 337       net::HostPortPair host_port_pair =
 338           net::HostPortPair::FromURL(request->url_request()->url());
 339       net::HttpServerProperties& http_server_properties =
 340           *request->url_request()->context()->http_server_properties();
 341       if (!http_server_properties.SupportsSpdy(host_port_pair)) {
 342         return true;
 343       }
 344     }
 345     return false;
 346   }
 347
 348   void SetRequestDelayable(ScheduledResourceRequest* request,
 349                            bool delayable) {
 350     if (request->accounted_as_delayable_request() == delayable)
 351       return;
 352     if (delayable)
 353       total_delayable_count_++;
 354     else
 355       total_delayable_count_--;
 356     request->set_accounted_as_delayable_request(delayable);
 357   }
 358
 359   bool ShouldKeepSearching(
 360       const net::HostPortPair& active_request_host) const {
 361     size_t same_host_count = 0;
 362     for (RequestSet::const_iterator it = in_flight_requests_.begin();
 363          it != in_flight_requests_.end(); ++it) {
 364       net::HostPortPair host_port_pair =
 365           net::HostPortPair::FromURL((*it)->url_request()->url());
 366       if (active_request_host.Equals(host_port_pair)) {
 367         same_host_count++;
 368         if (same_host_count >= kMaxNumDelayableRequestsPerHost)
 369           return true;
 370       }
 371     }
 372     return false;
 373   }
 374
 375   void StartRequest(ScheduledResourceRequest* request) {
 376     InsertInFlightRequest(request);
 377     request->Start();
 378   }
 379
 380   // ShouldStartRequest is the main scheduling algorithm.
 381   //
 382   // Requests are categorized into two categories:
 383   //
 384   // 1. Immediately issued requests, which are:
 385   //
 386   //   * Higher priority requests (>= net::LOW).
 387   //   * Synchronous requests.
 388   //   * Requests to SPDY-capable origin servers.
 389   //   * Non-HTTP[S] requests.
 390   //
 391   // 2. The remainder are delayable requests, which follow these rules:
 392   //
 393   //   * If no high priority requests are in flight, start loading low priority
 394   //      requests.
 395   //   * Once the renderer has a <body>, start loading delayable requests.
 396   //   * Never exceed 10 delayable requests in flight per client.
 397   //   * Never exceed 6 delayable requests for a given host.
 398   //   * Prior to <body>, allow one delayable request to load at a time.
 399   ShouldStartReqResult ShouldStartRequest(
 400       ScheduledResourceRequest* request) const {
 401     const net::URLRequest& url_request = *request->url_request();
 402     // TODO(simonjam): This may end up causing disk contention. We should
 403     // experiment with throttling if that happens.
 404     if (!url_request.url().SchemeIsHTTPOrHTTPS()) {
 405       return START_REQUEST;
 406     }
 407
 408     if (using_spdy_proxy_ && url_request.url().SchemeIs("http")) {
 409       return START_REQUEST;
 410     }
 411
 412     net::HttpServerProperties& http_server_properties =
 413         *url_request.context()->http_server_properties();
 414
 415     if (url_request.priority() >= net::LOW ||
 416         !ResourceRequestInfo::ForRequest(&url_request)->IsAsync()) {
 417       return START_REQUEST;
 418     }
 419
 420     net::HostPortPair host_port_pair =
 421         net::HostPortPair::FromURL(url_request.url());
 422
 423     // TODO(willchan): We should really improve this algorithm as described in
 424     // crbug.com/164101. Also, theoretically we should not count a SPDY request
 425     // against the delayable requests limit.
 426     if (http_server_properties.SupportsSpdy(host_port_pair)) {
 427       return START_REQUEST;
 428     }
 429
 430     size_t num_delayable_requests_in_flight = total_delayable_count_;
 431     if (num_delayable_requests_in_flight >= kMaxNumDelayableRequestsPerClient) {
 432       return DO_NOT_START_REQUEST_AND_STOP_SEARCHING;
 433     }
 434
 435     if (ShouldKeepSearching(host_port_pair)) {
 436       // There may be other requests for other hosts we'd allow,
 437       // so keep checking.
 438       return DO_NOT_START_REQUEST_AND_KEEP_SEARCHING;
 439     }
 440
 441     bool have_immediate_requests_in_flight =
 442         in_flight_requests_.size() > num_delayable_requests_in_flight;
 443     if (have_immediate_requests_in_flight && !has_body_ &&
 444         num_delayable_requests_in_flight != 0) {
 445       return DO_NOT_START_REQUEST_AND_STOP_SEARCHING;
 446     }
 447
 448     return START_REQUEST;
 449   }
 450
 451   void LoadAnyStartablePendingRequests() {
 452     // We iterate through all the pending requests, starting with the highest
 453     // priority one. For each entry, one of three things can happen:
 454     // 1) We start the request, remove it from the list, and keep checking.
 455     // 2) We do NOT start the request, but ShouldStartRequest() signals us that
 456     //     there may be room for other requests, so we keep checking and leave
 457     //     the previous request still in the list.
 458     // 3) We do not start the request, same as above, but StartRequest() tells
 459     //     us there's no point in checking any further requests.
 460     RequestQueue::NetQueue::iterator request_iter =
 461         pending_requests_.GetNextHighestIterator();
 462
 463     while (request_iter != pending_requests_.End()) {
 464       ScheduledResourceRequest* request = *request_iter;
 465       ShouldStartReqResult query_result = ShouldStartRequest(request);
 466
 467       if (query_result == START_REQUEST) {
 468         pending_requests_.Erase(request);
 469         StartRequest(request);
 470
 471         // StartRequest can modify the pending list, so we (re)start evaluation
 472         // from the currently highest priority request. Avoid copying a singular
 473         // iterator, which would trigger undefined behavior.
 474         if (pending_requests_.GetNextHighestIterator() ==
 475             pending_requests_.End())
 476           break;
 477         request_iter = pending_requests_.GetNextHighestIterator();
 478       } else if (query_result == DO_NOT_START_REQUEST_AND_KEEP_SEARCHING) {
 479         ++request_iter;
 480         continue;
 481       } else {
 482         DCHECK(query_result == DO_NOT_START_REQUEST_AND_STOP_SEARCHING);
 483         break;
 484       }
 485     }
 486   }
 487
 488   bool has_body_;
 489   bool using_spdy_proxy_;
 490   RequestQueue pending_requests_;
 491   RequestSet in_flight_requests_;
 492   // The number of delayable in-flight requests.
 493   size_t total_delayable_count_;
 494 };
 495
 496 ResourceScheduler::ResourceScheduler() {
 497 }
 498
 499 ResourceScheduler::~ResourceScheduler() {
 500   DCHECK(unowned_requests_.empty());
 501   DCHECK(client_map_.empty());
 502 }
 503
 504 scoped_ptr<ResourceThrottle> ResourceScheduler::ScheduleRequest(
 505     int child_id,
 506     int route_id,
 507     net::URLRequest* url_request) {
 508   DCHECK(CalledOnValidThread());
 509   ClientId client_id = MakeClientId(child_id, route_id);
 510   scoped_ptr<ScheduledResourceRequest> request(
 511       new ScheduledResourceRequest(client_id, url_request, this,
 512           RequestPriorityParams(url_request->priority(), 0)));
 513
 514   ClientMap::iterator it = client_map_.find(client_id);
 515   if (it == client_map_.end()) {
 516     // There are several ways this could happen:
 517     // 1. <a ping> requests don't have a route_id.
 518     // 2. Most unittests don't send the IPCs needed to register Clients.
 519     // 3. The tab is closed while a RequestResource IPC is in flight.
 520     unowned_requests_.insert(request.get());
 521     request->Start();
 522     return request.PassAs<ResourceThrottle>();
 523   }
 524
 525   Client* client = it->second;
 526   client->ScheduleRequest(url_request, request.get());
 527   return request.PassAs<ResourceThrottle>();
 528 }
 529
 530 void ResourceScheduler::RemoveRequest(ScheduledResourceRequest* request) {
 531   DCHECK(CalledOnValidThread());
 532   if (ContainsKey(unowned_requests_, request)) {
 533     unowned_requests_.erase(request);
 534     return;
 535   }
 536
 537   ClientMap::iterator client_it = client_map_.find(request->client_id());
 538   if (client_it == client_map_.end()) {
 539     return;
 540   }
 541
 542   Client* client = client_it->second;
 543   client->RemoveRequest(request);
 544 }
 545
 546 void ResourceScheduler::OnClientCreated(int child_id, int route_id) {
 547   DCHECK(CalledOnValidThread());
 548   ClientId client_id = MakeClientId(child_id, route_id);
 549   DCHECK(!ContainsKey(client_map_, client_id));
 550
 551   client_map_[client_id] = new Client;
 552 }
 553
 554 void ResourceScheduler::OnClientDeleted(int child_id, int route_id) {
 555   DCHECK(CalledOnValidThread());
 556   ClientId client_id = MakeClientId(child_id, route_id);
 557   DCHECK(ContainsKey(client_map_, client_id));
 558   ClientMap::iterator it = client_map_.find(client_id);
 559   if (it == client_map_.end())
 560     return;
 561
 562   Client* client = it->second;
 563
 564   // FYI, ResourceDispatcherHost cancels all of the requests after this function
 565   // is called. It should end up canceling all of the requests except for a
 566   // cross-renderer navigation.
 567   RequestSet client_unowned_requests = client->RemoveAllRequests();
 568   for (RequestSet::iterator it = client_unowned_requests.begin();
 569        it != client_unowned_requests.end(); ++it) {
 570     unowned_requests_.insert(*it);
 571   }
 572
 573   delete client;
 574   client_map_.erase(it);
 575 }
 576
 577 void ResourceScheduler::OnNavigate(int child_id, int route_id) {
 578   DCHECK(CalledOnValidThread());
 579   ClientId client_id = MakeClientId(child_id, route_id);
 580
 581   ClientMap::iterator it = client_map_.find(client_id);
 582   if (it == client_map_.end()) {
 583     // The client was likely deleted shortly before we received this IPC.
 584     return;
 585   }
 586
 587   Client* client = it->second;
 588   client->OnNavigate();
 589 }
 590
 591 void ResourceScheduler::OnWillInsertBody(int child_id, int route_id) {
 592   DCHECK(CalledOnValidThread());
 593   ClientId client_id = MakeClientId(child_id, route_id);
 594
 595   ClientMap::iterator it = client_map_.find(client_id);
 596   if (it == client_map_.end()) {
 597     // The client was likely deleted shortly before we received this IPC.
 598     return;
 599   }
 600
 601   Client* client = it->second;
 602   client->OnWillInsertBody();
 603 }
 604
 605 void ResourceScheduler::OnReceivedSpdyProxiedHttpResponse(
 606     int child_id,
 607     int route_id) {
 608   DCHECK(CalledOnValidThread());
 609   ClientId client_id = MakeClientId(child_id, route_id);
 610
 611   ClientMap::iterator client_it = client_map_.find(client_id);
 612   if (client_it == client_map_.end()) {
 613     return;
 614   }
 615
 616   Client* client = client_it->second;
 617   client->OnReceivedSpdyProxiedHttpResponse();
 618 }
 619
 620 void ResourceScheduler::ReprioritizeRequest(ScheduledResourceRequest* request,
 621                                             net::RequestPriority new_priority,
 622                                             int new_intra_priority_value) {
 623   if (request->url_request()->load_flags() & net::LOAD_IGNORE_LIMITS) {
 624     // We should not be re-prioritizing requests with the
 625     // IGNORE_LIMITS flag.
 626     NOTREACHED();
 627     return;
 628   }
 629   RequestPriorityParams new_priority_params(new_priority,
 630       new_intra_priority_value);
 631   RequestPriorityParams old_priority_params =
 632       request->get_request_priority_params();
 633
 634   DCHECK(old_priority_params != new_priority_params);
 635
 636   ClientMap::iterator client_it = client_map_.find(request->client_id());
 637   if (client_it == client_map_.end()) {
 638     // The client was likely deleted shortly before we received this IPC.
 639     request->url_request()->SetPriority(new_priority_params.priority);
 640     request->set_request_priority_params(new_priority_params);
 641     return;
 642   }
 643
 644   if (old_priority_params == new_priority_params)
 645     return;
 646
 647   Client *client = client_it->second;
 648   client->ReprioritizeRequest(
 649       request, old_priority_params, new_priority_params);
 650 }
 651
 652 ResourceScheduler::ClientId ResourceScheduler::MakeClientId(
 653     int child_id, int route_id) {
 654   return (static_cast<ResourceScheduler::ClientId>(child_id) << 32) | route_id;
 655 }
 656
 657 }  // namespace content