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chromium / chromium / src / 95ebb2b7ff6ac3909904d009a4efeaa4fa8acc56 / . / services / network / resource_scheduler / resource_scheduler.cc
blob: b2448737cb48174af1f1f07a2a08b6cff894450a [file] [log] [blame]
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "services/network/resource_scheduler/resource_scheduler.h"
#include <stdint.h>
#include <string>
#include <utility>
#include "base/bind.h"
#include "base/macros.h"
#include "base/metrics/field_trial.h"
#include "base/metrics/field_trial_params.h"
#include "base/metrics/histogram_functions.h"
#include "base/metrics/histogram_macros.h"
#include "base/optional.h"
#include "base/sequenced_task_runner.h"
#include "base/stl_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/supports_user_data.h"
#include "base/threading/thread_task_runner_handle.h"
#include "base/time/default_tick_clock.h"
#include "base/time/tick_clock.h"
#include "base/trace_event/trace_event.h"
#include "net/base/host_port_pair.h"
#include "net/base/load_flags.h"
#include "net/base/request_priority.h"
#include "net/http/http_server_properties.h"
#include "net/log/net_log.h"
#include "net/nqe/effective_connection_type_observer.h"
#include "net/nqe/network_quality_estimator.h"
#include "net/nqe/peer_to_peer_connections_count_observer.h"
#include "net/url_request/url_request.h"
#include "net/url_request/url_request_context.h"
#include "services/network/public/cpp/features.h"
#include "services/network/public/mojom/network_context.mojom.h"
#include "url/scheme_host_port.h"
namespace network {
namespace {
enum StartMode { START_SYNC, START_ASYNC };
// Flags identifying various attributes of the request that are used
// when making scheduling decisions.
using RequestAttributes = uint8_t;
const RequestAttributes kAttributeNone = 0x00;
const RequestAttributes kAttributeInFlight = 0x01;
const RequestAttributes kAttributeDelayable = 0x02;
const RequestAttributes kAttributeLayoutBlocking = 0x04;
// Reasons why pending requests may be started. For logging only.
enum class RequestStartTrigger {
NONE,
COMPLETION_PRE_BODY,
COMPLETION_POST_BODY,
BODY_REACHED,
CLIENT_KILL,
SPDY_PROXY_DETECTED,
REQUEST_REPRIORITIZED,
LONG_QUEUED_REQUESTS_TIMER_FIRED,
EFFECTIVE_CONNECTION_TYPE_CHANGED,
PEER_TO_PEER_CONNECTIONS_COUNT_CHANGED,
};
const char* RequestStartTriggerString(RequestStartTrigger trigger) {
switch (trigger) {
case RequestStartTrigger::NONE:
return "NONE";
case RequestStartTrigger::COMPLETION_PRE_BODY:
return "COMPLETION_PRE_BODY";
case RequestStartTrigger::COMPLETION_POST_BODY:
return "COMPLETION_POST_BODY";
case RequestStartTrigger::BODY_REACHED:
return "BODY_REACHED";
case RequestStartTrigger::CLIENT_KILL:
return "CLIENT_KILL";
case RequestStartTrigger::SPDY_PROXY_DETECTED:
return "SPDY_PROXY_DETECTED";
case RequestStartTrigger::REQUEST_REPRIORITIZED:
return "REQUEST_REPRIORITIZED";
case RequestStartTrigger::LONG_QUEUED_REQUESTS_TIMER_FIRED:
return "LONG_QUEUED_REQUESTS_TIMER_FIRED";
case RequestStartTrigger::EFFECTIVE_CONNECTION_TYPE_CHANGED:
return "EFFECTIVE_CONNECTION_TYPE_CHANGED";
case RequestStartTrigger::PEER_TO_PEER_CONNECTIONS_COUNT_CHANGED:
return "PEER_TO_PEER_CONNECTIONS_COUNT_CHANGED";
}
}
} // namespace
// The maximum number of requests to allow be in-flight at any point in time per
// host. This limit does not apply to hosts that support request prioritization
// when |delay_requests_on_multiplexed_connections| is true.
static const size_t kMaxNumDelayableRequestsPerHostPerClient = 6;
// The maximum number of delayable requests to allow to be in-flight at any
// point in time while in the layout-blocking phase of loading.
static const size_t kMaxNumDelayableWhileLayoutBlockingPerClient = 1;
// The priority level below which resources are considered to be delayable.
static const net::RequestPriority kDelayablePriorityThreshold = net::MEDIUM;
// The number of in-flight layout-blocking requests above which all delayable
// requests should be blocked.
static const size_t kInFlightNonDelayableRequestCountPerClientThreshold = 1;
// Returns the duration after which the timer to dispatch queued requests should
// fire.
base::TimeDelta GetQueuedRequestsDispatchPeriodicity() {
// This primarily affects two types of requests:
// (i) Requests that have been queued for too long, and firing of timer may
// result in some of those requests being dispatched to the network.
// Such requests need to be queued for at least 15 seconds before they can be
// dispatched.
// (ii) Requests that were throttled proactively in anticipation of arrival
// of higher priority requests. These requests need to be unthrottled after
// their queuing duration expires. The queuing duration is a function of HTTP
// RTT and can be of the order of 100 milliseconds.
//
// Note that the timer is active and fires periodically only if
// there is at least one queued request.
// When kProactivelyThrottleLowPriorityRequests is not enabled, it's
// sufficient to choose a longer periodicity (implying that timer will be
// fired less frequently) since the requests are queued for at least 15
// seconds anyways. Firing the timer a bit later is not going to delay the
// dispatch of the request by a significant amount.
if (!base::FeatureList::IsEnabled(
features::kProactivelyThrottleLowPriorityRequests)) {
return base::TimeDelta::FromSeconds(5);
}
// Choosing 100 milliseconds as the checking interval ensurs that the
// queue is not checked too frequently. The interval is also not too long, so
// we do not expect too many requests to go on the network at the
// same time.
return base::TimeDelta::FromMilliseconds(100);
}
struct ResourceScheduler::RequestPriorityParams {
RequestPriorityParams()
: priority(net::DEFAULT_PRIORITY), intra_priority(0) {}
RequestPriorityParams(net::RequestPriority priority, int intra_priority)
: priority(priority), intra_priority(intra_priority) {}
bool operator==(const RequestPriorityParams& other) const {
return (priority == other.priority) &&
(intra_priority == other.intra_priority);
}
bool operator!=(const RequestPriorityParams& other) const {
return !(*this == other);
}
bool GreaterThan(const RequestPriorityParams& other) const {
if (priority != other.priority)
return priority > other.priority;
return intra_priority > other.intra_priority;
}
net::RequestPriority priority;
int intra_priority;
};
class ResourceScheduler::RequestQueue {
public:
using NetQueue =
std::multiset<ScheduledResourceRequestImpl*, ScheduledResourceSorter>;
RequestQueue() : fifo_ordering_ids_(0) {}
~RequestQueue() {}
// Adds |request| to the queue with given |priority|.
void Insert(ScheduledResourceRequestImpl* request);
// Removes |request| from the queue.
void Erase(ScheduledResourceRequestImpl* request) {
PointerMap::iterator it = pointers_.find(request);
CHECK(it != pointers_.end());
queue_.erase(it->second);
pointers_.erase(it);
}
NetQueue::iterator GetNextHighestIterator() { return queue_.begin(); }
NetQueue::iterator End() { return queue_.end(); }
// Returns true if |request| is queued.
bool IsQueued(ScheduledResourceRequestImpl* request) const {
return base::Contains(pointers_, request);
}
// Returns true if no requests are queued.
bool IsEmpty() const { return queue_.empty(); }
private:
using PointerMap =
std::map<ScheduledResourceRequestImpl*, NetQueue::iterator>;
uint32_t MakeFifoOrderingId() {
fifo_ordering_ids_ += 1;
return fifo_ordering_ids_;
}
// Used to create an ordering ID for scheduled resources so that resources
// with same priority/intra_priority stay in fifo order.
uint32_t fifo_ordering_ids_;
NetQueue queue_;
PointerMap pointers_;
};
ResourceScheduler::ScheduledResourceRequest::ScheduledResourceRequest() {}
ResourceScheduler::ScheduledResourceRequest::~ScheduledResourceRequest() {}
void ResourceScheduler::ScheduledResourceRequest::RunResumeCallback() {
std::move(resume_callback_).Run();
}
// This is the handle we return to the ResourceDispatcherHostImpl so it can
// interact with the request.
class ResourceScheduler::ScheduledResourceRequestImpl
: public ScheduledResourceRequest {
public:
ScheduledResourceRequestImpl(const ClientId& client_id,
net::URLRequest* request,
ResourceScheduler* scheduler,
const RequestPriorityParams& priority,
bool is_async)
: client_id_(client_id),
request_(request),
ready_(false),
deferred_(false),
is_async_(is_async),
attributes_(kAttributeNone),
scheduler_(scheduler),
priority_(priority),
fifo_ordering_(0),
peak_delayable_requests_in_flight_(0u),
host_port_pair_(net::HostPortPair::FromURL(request->url())) {
DCHECK(!request_->GetUserData(kUserDataKey));
request_->SetUserData(kUserDataKey, std::make_unique<UnownedPointer>(this));
}
~ScheduledResourceRequestImpl() override {
if ((attributes_ & kAttributeLayoutBlocking) == kAttributeLayoutBlocking) {
UMA_HISTOGRAM_COUNTS_100(
"ResourceScheduler.PeakDelayableRequestsInFlight.LayoutBlocking",
peak_delayable_requests_in_flight_);
}
if (!((attributes_ & kAttributeDelayable) == kAttributeDelayable)) {
UMA_HISTOGRAM_COUNTS_100(
"ResourceScheduler.PeakDelayableRequestsInFlight.NonDelayable",
peak_delayable_requests_in_flight_);
}
request_->RemoveUserData(kUserDataKey);
scheduler_->RemoveRequest(this);
}
static ScheduledResourceRequestImpl* ForRequest(net::URLRequest* request) {
UnownedPointer* pointer =
static_cast<UnownedPointer*>(request->GetUserData(kUserDataKey));
return pointer ? pointer->get() : nullptr;
}
// Starts the request. If |start_mode| is START_ASYNC, the request will not
// be started immediately.
void Start(StartMode start_mode) {
DCHECK(!ready_);
// If the request was cancelled, do nothing.
if (!request_->status().is_success())
return;
// If the request was deferred, need to start it. Otherwise, will just not
// defer starting it in the first place, and the value of |start_mode|
// makes no difference.
if (deferred_) {
// If can't start the request synchronously, post a task to start the
// request.
if (start_mode == START_ASYNC) {
scheduler_->task_runner()->PostTask(
FROM_HERE,
base::BindOnce(&ScheduledResourceRequestImpl::Start,
weak_ptr_factory_.GetWeakPtr(), START_SYNC));
return;
}
deferred_ = false;
RunResumeCallback();
}
ready_ = true;
}
void UpdateDelayableRequestsInFlight(size_t delayable_requests_in_flight) {
peak_delayable_requests_in_flight_ = std::max(
peak_delayable_requests_in_flight_, delayable_requests_in_flight);
}
void set_request_priority_params(const RequestPriorityParams& priority) {
priority_ = priority;
}
const RequestPriorityParams& get_request_priority_params() const {
return priority_;
}
const ClientId& client_id() const { return client_id_; }
net::URLRequest* url_request() { return request_; }
const net::URLRequest* url_request() const { return request_; }
bool is_async() const { return is_async_; }
uint32_t fifo_ordering() const { return fifo_ordering_; }
void set_fifo_ordering(uint32_t fifo_ordering) {
fifo_ordering_ = fifo_ordering;
}
RequestAttributes attributes() const { return attributes_; }
void set_attributes(RequestAttributes attributes) {
attributes_ = attributes;
}
const net::HostPortPair& host_port_pair() const { return host_port_pair_; }
private:
class UnownedPointer : public base::SupportsUserData::Data {
public:
explicit UnownedPointer(ScheduledResourceRequestImpl* pointer)
: pointer_(pointer) {}
ScheduledResourceRequestImpl* get() const { return pointer_; }
private:
ScheduledResourceRequestImpl* const pointer_;
DISALLOW_COPY_AND_ASSIGN(UnownedPointer);
};
static const void* const kUserDataKey;
// ScheduledResourceRequest implemnetation
void WillStartRequest(bool* defer) override { deferred_ = *defer = !ready_; }
const ClientId client_id_;
net::URLRequest* request_;
bool ready_;
bool deferred_;
bool is_async_;
RequestAttributes attributes_;
ResourceScheduler* scheduler_;
RequestPriorityParams priority_;
uint32_t fifo_ordering_;
// Maximum number of delayable requests in-flight when |this| was in-flight.
size_t peak_delayable_requests_in_flight_;
// Cached to excessive recomputation in ReachedMaxRequestsPerHostPerClient().
const net::HostPortPair host_port_pair_;
base::WeakPtrFactory<ResourceScheduler::ScheduledResourceRequestImpl>
weak_ptr_factory_{this};
DISALLOW_COPY_AND_ASSIGN(ScheduledResourceRequestImpl);
};
const void* const
ResourceScheduler::ScheduledResourceRequestImpl::kUserDataKey =
&ResourceScheduler::ScheduledResourceRequestImpl::kUserDataKey;
bool ResourceScheduler::ScheduledResourceSorter::operator()(
const ScheduledResourceRequestImpl* a,
const ScheduledResourceRequestImpl* b) const {
// Want the set to be ordered first by decreasing priority, then by
// decreasing intra_priority.
// ie. with (priority, intra_priority)
// [(1, 0), (1, 0), (0, 100), (0, 0)]
if (a->get_request_priority_params() != b->get_request_priority_params())
return a->get_request_priority_params().GreaterThan(
b->get_request_priority_params());
// If priority/intra_priority is the same, fall back to fifo ordering.
// std::multiset doesn't guarantee this until c++11.
return a->fifo_ordering() < b->fifo_ordering();
}
void ResourceScheduler::RequestQueue::Insert(
ScheduledResourceRequestImpl* request) {
DCHECK(!base::Contains(pointers_, request));
request->set_fifo_ordering(MakeFifoOrderingId());
pointers_[request] = queue_.insert(request);
}
// Each client represents a tab.
class ResourceScheduler::Client
: public net::EffectiveConnectionTypeObserver,
public net::PeerToPeerConnectionsCountObserver {
public:
Client(bool is_browser_client,
net::NetworkQualityEstimator* network_quality_estimator,
ResourceScheduler* resource_scheduler,
const base::TickClock* tick_clock)
: is_browser_client_(is_browser_client),
in_flight_delayable_count_(0),
total_layout_blocking_count_(0),
num_skipped_scans_due_to_scheduled_start_(0),
network_quality_estimator_(network_quality_estimator),
resource_scheduler_(resource_scheduler),
tick_clock_(tick_clock) {
DCHECK(tick_clock_);
if (network_quality_estimator_) {
effective_connection_type_ =
network_quality_estimator_->GetEffectiveConnectionType();
UpdateParamsForNetworkQuality();
network_quality_estimator_->AddEffectiveConnectionTypeObserver(this);
network_quality_estimator_->AddPeerToPeerConnectionsCountObserver(this);
}
}
~Client() override {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (network_quality_estimator_) {
network_quality_estimator_->RemoveEffectiveConnectionTypeObserver(this);
network_quality_estimator_->RemovePeerToPeerConnectionsCountObserver(
this);
}
}
void ScheduleRequest(const net::URLRequest& url_request,
ScheduledResourceRequestImpl* request) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
SetRequestAttributes(request, DetermineRequestAttributes(request));
ShouldStartReqResult should_start = ShouldStartRequest(request);
if (should_start == START_REQUEST) {
// New requests can be started synchronously without issue.
StartRequest(request, START_SYNC, RequestStartTrigger::NONE);
} else {
pending_requests_.Insert(request);
}
}
void RemoveRequest(ScheduledResourceRequestImpl* request) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (pending_requests_.IsQueued(request)) {
pending_requests_.Erase(request);
DCHECK(!base::Contains(in_flight_requests_, request));
} else {
// Record metrics.
if (!RequestAttributesAreSet(request->attributes(), kAttributeDelayable))
last_non_delayable_request_end_ = tick_clock_->NowTicks();
RecordNetworkContentionMetrics(*request);
EraseInFlightRequest(request);
// Removing this request may have freed up another to load.
LoadAnyStartablePendingRequests(
RequestStartTrigger::COMPLETION_POST_BODY);
}
}
RequestSet StartAndRemoveAllRequests() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
// First start any pending requests so that they will be moved into
// in_flight_requests_. This may exceed the limits
// kDefaultMaxNumDelayableRequestsPerClient and
// kMaxNumDelayableRequestsPerHostPerClient, so this method must not do
// anything that depends on those limits before calling
// ClearInFlightRequests() below.
while (!pending_requests_.IsEmpty()) {
ScheduledResourceRequestImpl* request =
*pending_requests_.GetNextHighestIterator();
pending_requests_.Erase(request);
// Starting requests asynchronously ensures no side effects, and avoids
// starting a bunch of requests that may be about to be deleted.
StartRequest(request, START_ASYNC, RequestStartTrigger::CLIENT_KILL);
}
RequestSet unowned_requests;
for (RequestSet::iterator it = in_flight_requests_.begin();
it != in_flight_requests_.end(); ++it) {
unowned_requests.insert(*it);
(*it)->set_attributes(kAttributeNone);
}
ClearInFlightRequests();
return unowned_requests;
}
void ReprioritizeRequest(ScheduledResourceRequestImpl* request,
RequestPriorityParams old_priority_params,
RequestPriorityParams new_priority_params) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
request->url_request()->SetPriority(new_priority_params.priority);
request->set_request_priority_params(new_priority_params);
SetRequestAttributes(request, DetermineRequestAttributes(request));
if (!pending_requests_.IsQueued(request)) {
DCHECK(base::Contains(in_flight_requests_, request));
// Request has already started.
return;
}
pending_requests_.Erase(request);
pending_requests_.Insert(request);
if (new_priority_params.priority > old_priority_params.priority) {
// Check if this request is now able to load at its new priority.
ScheduleLoadAnyStartablePendingRequests(
RequestStartTrigger::REQUEST_REPRIORITIZED);
}
}
// Updates the params based on the current network quality estimate.
void UpdateParamsForNetworkQuality() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
params_for_network_quality_ =
resource_scheduler_->resource_scheduler_params_manager_
.GetParamsForEffectiveConnectionType(
network_quality_estimator_
? effective_connection_type_
: net::EFFECTIVE_CONNECTION_TYPE_UNKNOWN);
}
void OnLongQueuedRequestsDispatchTimerFired() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
LoadAnyStartablePendingRequests(
RequestStartTrigger::LONG_QUEUED_REQUESTS_TIMER_FIRED);
}
bool HasNoPendingRequests() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
return pending_requests_.IsEmpty();
}
bool IsActiveResourceSchedulerClient() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
return (!pending_requests_.IsEmpty() || !in_flight_requests_.empty());
}
size_t CountInflightDelayableRequests() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
return in_flight_delayable_count_;
}
size_t CountInflightNonDelayableRequests() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
return in_flight_requests_.size() - in_flight_delayable_count_;
}
size_t CountInflightLayoutBlockingRequests() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
return total_layout_blocking_count_;
}
private:
enum ShouldStartReqResult {
DO_NOT_START_REQUEST_AND_STOP_SEARCHING,
DO_NOT_START_REQUEST_AND_KEEP_SEARCHING,
START_REQUEST
};
// net::EffectiveConnectionTypeObserver:
void OnEffectiveConnectionTypeChanged(
net::EffectiveConnectionType effective_connection_type) override {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (effective_connection_type_ == effective_connection_type)
return;
effective_connection_type_ = effective_connection_type;
UpdateParamsForNetworkQuality();
// Change in network quality may allow |this| to dispatch more requests.
LoadAnyStartablePendingRequests(
RequestStartTrigger::EFFECTIVE_CONNECTION_TYPE_CHANGED);
}
// net::PeerToPeerConnectionsCountObserver:
void OnPeerToPeerConnectionsCountChange(uint32_t count) override {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (p2p_connections_count_ == count)
return;
if (p2p_connections_count_ > 0 && count == 0) {
// If the count of P2P connections went down to 0, start a timer. When the
// timer fires, the queued browser-initiated requests would be dispatched.
p2p_connections_count_end_timestamp_ = tick_clock_->NowTicks();
p2p_connections_count_ended_timer_.Stop();
p2p_connections_count_ended_timer_.Start(
FROM_HERE,
resource_scheduler_->resource_scheduler_params_manager_
.TimeToPauseHeavyBrowserInitiatedRequestsAfterEndOfP2PConnections(),
this,
&ResourceScheduler::Client::OnP2PConnectionsCountEndedTimerFired);
}
p2p_connections_count_ = count;
if (p2p_connections_count_ > 0 &&
!p2p_connections_count_active_timestamp_.has_value()) {
p2p_connections_count_active_timestamp_ = base::TimeTicks::Now();
}
if (p2p_connections_count_ == 0 &&
p2p_connections_count_active_timestamp_.has_value()) {
p2p_connections_count_active_timestamp_ = base::nullopt;
}
LoadAnyStartablePendingRequests(
RequestStartTrigger::PEER_TO_PEER_CONNECTIONS_COUNT_CHANGED);
}
void OnP2PConnectionsCountEndedTimerFired() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
LoadAnyStartablePendingRequests(
RequestStartTrigger::PEER_TO_PEER_CONNECTIONS_COUNT_CHANGED);
}
// Records the metrics related to number of requests in flight.
void RecordRequestCountMetrics() const {
UMA_HISTOGRAM_COUNTS_100("ResourceScheduler.RequestsCount.All",
in_flight_requests_.size());
UMA_HISTOGRAM_COUNTS_100("ResourceScheduler.RequestsCount.Delayable",
in_flight_delayable_count_);
UMA_HISTOGRAM_COUNTS_100(
"ResourceScheduler.RequestsCount.NonDelayable",
in_flight_requests_.size() - in_flight_delayable_count_);
UMA_HISTOGRAM_COUNTS_100(
"ResourceScheduler.RequestsCount.TotalLayoutBlocking",
total_layout_blocking_count_);
resource_scheduler_->RecordGlobalRequestCountMetrics();
}
void InsertInFlightRequest(ScheduledResourceRequestImpl* request) {
in_flight_requests_.insert(request);
SetRequestAttributes(request, DetermineRequestAttributes(request));
RecordRequestCountMetrics();
if (RequestAttributesAreSet(request->attributes(), kAttributeDelayable)) {
// Notify all in-flight with the new count of in-flight delayable
// requests.
for (RequestSet::const_iterator it = in_flight_requests_.begin();
it != in_flight_requests_.end(); ++it) {
(*it)->UpdateDelayableRequestsInFlight(in_flight_delayable_count_);
}
}
if (RequestAttributesAreSet(request->attributes(),
kAttributeLayoutBlocking) ||
!RequestAttributesAreSet(request->attributes(), kAttributeDelayable)) {
// |request| is either a layout blocking or a non-delayable request.
request->UpdateDelayableRequestsInFlight(in_flight_delayable_count_);
}
}
void EraseInFlightRequest(ScheduledResourceRequestImpl* request) {
size_t erased = in_flight_requests_.erase(request);
DCHECK_EQ(1u, erased);
// Clear any special state that we were tracking for this request.
SetRequestAttributes(request, kAttributeNone);
}
void ClearInFlightRequests() {
in_flight_requests_.clear();
in_flight_delayable_count_ = 0;
total_layout_blocking_count_ = 0;
}
size_t CountRequestsWithAttributes(
const RequestAttributes attributes,
ScheduledResourceRequestImpl* current_request) {
size_t matching_request_count = 0;
for (RequestSet::const_iterator it = in_flight_requests_.begin();
it != in_flight_requests_.end(); ++it) {
if (RequestAttributesAreSet((*it)->attributes(), attributes))
matching_request_count++;
}
if (!RequestAttributesAreSet(attributes, kAttributeInFlight)) {
bool current_request_is_pending = false;
for (RequestQueue::NetQueue::const_iterator it =
pending_requests_.GetNextHighestIterator();
it != pending_requests_.End(); ++it) {
if (RequestAttributesAreSet((*it)->attributes(), attributes))
matching_request_count++;
if (*it == current_request)
current_request_is_pending = true;
}
// Account for the current request if it is not in one of the lists yet.
if (current_request &&
!base::Contains(in_flight_requests_, current_request) &&
!current_request_is_pending) {
if (RequestAttributesAreSet(current_request->attributes(), attributes))
matching_request_count++;
}
}
return matching_request_count;
}
bool RequestAttributesAreSet(RequestAttributes request_attributes,
RequestAttributes matching_attributes) const {
return (request_attributes & matching_attributes) == matching_attributes;
}
void SetRequestAttributes(ScheduledResourceRequestImpl* request,
RequestAttributes attributes) {
RequestAttributes old_attributes = request->attributes();
if (old_attributes == attributes)
return;
if (RequestAttributesAreSet(old_attributes,
kAttributeInFlight | kAttributeDelayable)) {
in_flight_delayable_count_--;
}
if (RequestAttributesAreSet(old_attributes, kAttributeLayoutBlocking))
total_layout_blocking_count_--;
if (RequestAttributesAreSet(attributes,
kAttributeInFlight | kAttributeDelayable)) {
in_flight_delayable_count_++;
}
if (RequestAttributesAreSet(attributes, kAttributeLayoutBlocking))
total_layout_blocking_count_++;
request->set_attributes(attributes);
DCHECK_EQ(CountRequestsWithAttributes(
kAttributeInFlight | kAttributeDelayable, request),
in_flight_delayable_count_);
DCHECK_EQ(CountRequestsWithAttributes(kAttributeLayoutBlocking, request),
total_layout_blocking_count_);
}
RequestAttributes DetermineRequestAttributes(
ScheduledResourceRequestImpl* request) {
RequestAttributes attributes = kAttributeNone;
if (base::Contains(in_flight_requests_, request))
attributes |= kAttributeInFlight;
if (RequestAttributesAreSet(request->attributes(),
kAttributeLayoutBlocking)) {
// If a request is already marked as layout-blocking make sure to keep the
// attribute across redirects.
attributes |= kAttributeLayoutBlocking;
} else if (request->url_request()->priority() <
kDelayablePriorityThreshold) {
if (params_for_network_quality_
.delay_requests_on_multiplexed_connections) {
// Resources below the delayable priority threshold that are considered
// delayable.
attributes |= kAttributeDelayable;
} else {
// Resources below the delayable priority threshold that are being
// requested from a server that does not support native prioritization
// are considered delayable.
url::SchemeHostPort scheme_host_port(request->url_request()->url());
net::HttpServerProperties& http_server_properties =
*request->url_request()->context()->http_server_properties();
if (!http_server_properties.SupportsRequestPriority(
scheme_host_port,
request->url_request()->network_isolation_key())) {
attributes |= kAttributeDelayable;
}
}
}
return attributes;
}
bool ReachedMaxRequestsPerHostPerClient(
const net::HostPortPair& active_request_host,
bool supports_priority) const {
// This method should not be called for requests to origins that support
// prioritization (aka multiplexing) unless one of the experiments to
// throttle priority requests is enabled.
DCHECK(
!supports_priority ||
params_for_network_quality_.delay_requests_on_multiplexed_connections);
// kMaxNumDelayableRequestsPerHostPerClient limit does not apply to servers
// that support request priorities when
// |delay_requests_on_multiplexed_connections| is true. If
// |delay_requests_on_multiplexed_connections| is false, then
// kMaxNumDelayableRequestsPerHostPerClient limit still applies to other
// experiments that delay priority requests.
if (supports_priority &&
params_for_network_quality_.delay_requests_on_multiplexed_connections) {
return false;
}
size_t same_host_count = 0;
for (RequestSet::const_iterator it = in_flight_requests_.begin();
it != in_flight_requests_.end(); ++it) {
if (active_request_host.Equals((*it)->host_port_pair())) {
same_host_count++;
if (same_host_count >= kMaxNumDelayableRequestsPerHostPerClient)
return true;
}
}
return false;
}
void RecordMetricsOnStartRequest(const ScheduledResourceRequestImpl& request,
base::TimeTicks ticks_now) const {
const size_t non_delayable_requests_in_flight_count =
in_flight_requests_.size() - in_flight_delayable_count_;
// Record the number of delayable requests in-flight when a non-delayable
// request starts.
if (!RequestAttributesAreSet(request.attributes(), kAttributeDelayable)) {
if (non_delayable_requests_in_flight_count > 0) {
if (last_non_delayable_request_start_) {
UMA_HISTOGRAM_MEDIUM_TIMES(
"ResourceScheduler.NonDelayableLastStartToNonDelayableStart."
"NonDelayableInFlight",
ticks_now - last_non_delayable_request_start_.value());
}
} else {
if (last_non_delayable_request_end_) {
UMA_HISTOGRAM_MEDIUM_TIMES(
"ResourceScheduler.NonDelayableLastEndToNonDelayableStart."
"NonDelayableNotInFlight",
ticks_now - last_non_delayable_request_end_.value());
}
}
UMA_HISTOGRAM_COUNTS_100(
"ResourceScheduler.NumDelayableRequestsInFlightAtStart.NonDelayable",
in_flight_delayable_count_);
if (last_non_delayable_request_start_.has_value()) {
UMA_HISTOGRAM_MEDIUM_TIMES(
"ResourceScheduler.NonDelayableLastStartToNonDelayableStart",
ticks_now - last_non_delayable_request_start_.value());
}
if (last_non_delayable_request_end_.has_value()) {
UMA_HISTOGRAM_MEDIUM_TIMES(
"ResourceScheduler.NonDelayableLastEndToNonDelayableStart",
ticks_now - last_non_delayable_request_end_.value());
}
// Record time since last non-delayable request start or end, whichever
// happened later.
base::Optional<base::TimeTicks> last_non_delayable_request_start_or_end;
if (last_non_delayable_request_start_.has_value() &&
!last_non_delayable_request_end_.has_value()) {
last_non_delayable_request_start_or_end =
last_non_delayable_request_start_;
} else if (!last_non_delayable_request_start_.has_value() &&
last_non_delayable_request_end_.has_value()) {
last_non_delayable_request_start_or_end =
last_non_delayable_request_end_;
} else if (last_non_delayable_request_start_.has_value() &&
last_non_delayable_request_end_.has_value()) {
last_non_delayable_request_start_or_end =
std::max(last_non_delayable_request_start_.value(),
last_non_delayable_request_end_.value());
}
if (last_non_delayable_request_start_or_end) {
UMA_HISTOGRAM_MEDIUM_TIMES(
"ResourceScheduler.NonDelayableLastStartOrEndToNonDelayableStart",
ticks_now - last_non_delayable_request_start_or_end.value());
}
}
}
void StartRequest(ScheduledResourceRequestImpl* request,
StartMode start_mode,
RequestStartTrigger trigger) {
const base::TimeTicks ticks_now = tick_clock_->NowTicks();
// Only log on requests that were blocked by the ResourceScheduler.
if (start_mode == START_ASYNC) {
DCHECK_NE(RequestStartTrigger::NONE, trigger);
request->url_request()->net_log().AddEventWithStringParams(
net::NetLogEventType::RESOURCE_SCHEDULER_REQUEST_STARTED, "trigger",
RequestStartTriggerString(trigger));
}
if (request)
RecordMetricsOnStartRequest(*request, ticks_now);
DCHECK(!request->url_request()->creation_time().is_null());
base::TimeDelta queuing_duration =
ticks_now - request->url_request()->creation_time();
base::UmaHistogramMediumTimes(
"ResourceScheduler.RequestQueuingDuration.Priority" +
base::NumberToString(
request->get_request_priority_params().priority),
queuing_duration);
// Update the start time of the non-delayble request.
if (!RequestAttributesAreSet(request->attributes(), kAttributeDelayable))
last_non_delayable_request_start_ = ticks_now;
InsertInFlightRequest(request);
request->Start(start_mode);
}
// Returns true if |request| should be throttled to avoid network contention
// with active P2P connections.
bool ShouldThrottleBrowserInitiatedRequestDueToP2PConnections(
const ScheduledResourceRequestImpl& request) const {
DCHECK(is_browser_client_);
if (!base::FeatureList::IsEnabled(
features::kPauseBrowserInitiatedHeavyTrafficForP2P)) {
return false;
}
if (p2p_connections_count_ == 0) {
// If the current count of P2P connections is 0, then check when was the
// last time when there was an active P2P connection. If that timestamp is
// recent, it's a heuristic indication that a new P2P connection may
// start soon. To avoid network contention for that connection, keep
// throttling browser-initiated requests.
if (!p2p_connections_count_end_timestamp_.has_value())
return false;
bool p2p_connections_ended_long_back =
(tick_clock_->NowTicks() -
p2p_connections_count_end_timestamp_.value()) >=
resource_scheduler_->resource_scheduler_params_manager_
.TimeToPauseHeavyBrowserInitiatedRequestsAfterEndOfP2PConnections();
if (p2p_connections_ended_long_back)
return false;
// If there are no currently active P2P connections, and the last
// connection ended recently, then |p2p_connections_count_ended_timer_|
// must be running. When |p2p_connections_count_ended_timer_| fires,
// queued browser-initiated requests would be dispatched.
DCHECK(p2p_connections_count_ended_timer_.IsRunning());
}
// Only throttle when effective connection type is between Slow2G and 3G.
if (effective_connection_type_ <= net::EFFECTIVE_CONNECTION_TYPE_OFFLINE ||
effective_connection_type_ >= net::EFFECTIVE_CONNECTION_TYPE_4G) {
return false;
}
if (request.url_request()->priority() == net::HIGHEST)
return false;
if (p2p_connections_count_ > 0) {
base::TimeDelta time_since_p2p_connections_active =
tick_clock_->NowTicks() -
p2p_connections_count_active_timestamp_.value();
base::Optional<base::TimeDelta> max_wait_time_p2p_connections =
resource_scheduler_->resource_scheduler_params_manager_
.max_wait_time_p2p_connections();
if (time_since_p2p_connections_active >
max_wait_time_p2p_connections.value()) {
return false;
}
}
// Check other request specific constraints.
const net::NetworkTrafficAnnotationTag& traffic_annotation =
request.url_request()->traffic_annotation();
const int32_t unique_id_hash_code = traffic_annotation.unique_id_hash_code;
if (!resource_scheduler_->resource_scheduler_params_manager_
.CanThrottleNetworkTrafficAnnotationHash(unique_id_hash_code)) {
return false;
}
return true;
}
// Records metrics on browser initiated requests. Called when the request is
// dispatched to the network.
void RecordMetricsForBrowserInitiatedRequestsOnNetworkDispatch(
const ScheduledResourceRequestImpl& request) const {
const net::NetworkTrafficAnnotationTag& traffic_annotation =
request.url_request()->traffic_annotation();
const int32_t unique_id_hash_code = traffic_annotation.unique_id_hash_code;
// Metrics are recorded only for browser initiated requests that are
// eligible for throttling.
if (!resource_scheduler_->resource_scheduler_params_manager_
.CanThrottleNetworkTrafficAnnotationHash(unique_id_hash_code)) {
return;
}
base::TimeDelta queuing_duration =
tick_clock_->NowTicks() - request.url_request()->creation_time();
UMA_HISTOGRAM_LONG_TIMES(
"ResourceScheduler.BrowserInitiatedHeavyRequest.QueuingDuration",
queuing_duration);
}
// ShouldStartRequest is the main scheduling algorithm.
//
// Requests are evaluated on five attributes:
//
// 1. Non-delayable requests:
// * Synchronous requests.
// * Non-HTTP[S] requests.
//
// 2. Requests to request-priority-capable origin servers.
//
// 3. High-priority requests:
// * Higher priority requests (>= net::LOW).
//
// 4. Layout-blocking requests:
// * High-priority requests (> net::LOW) initiated before the renderer has
// a <body>.
//
// 5. Low priority requests
//
// The following rules are followed:
//
// All types of requests:
// * Non-delayable, High-priority and request-priority capable requests are
// issued immediately.
// * Low priority requests are delayable.
// * While kInFlightNonDelayableRequestCountPerClientThreshold
// layout-blocking requests are loading or the body tag has not yet been
// parsed, limit the number of delayable requests that may be in flight
// to kMaxNumDelayableWhileLayoutBlockingPerClient.
// * If no high priority or layout-blocking requests are in flight, start
// loading delayable requests.
// * Never exceed 10 delayable requests in flight per client.
// * Never exceed 6 delayable requests for a given host.
ShouldStartReqResult ShouldStartRequest(
ScheduledResourceRequestImpl* request) const {
if (!resource_scheduler_->enabled())
return START_REQUEST;
// Browser requests are treated differently since they are not user-facing.
if (is_browser_client_) {
if (ShouldThrottleBrowserInitiatedRequestDueToP2PConnections(*request)) {
return DO_NOT_START_REQUEST_AND_KEEP_SEARCHING;
}
RecordMetricsForBrowserInitiatedRequestsOnNetworkDispatch(*request);
return START_REQUEST;
}
const net::URLRequest& url_request = *request->url_request();
// Syncronous requests could block the entire render, which could impact
// user-observable Clients.
if (!request->is_async())
return START_REQUEST;
// TODO(simonjam): This may end up causing disk contention. We should
// experiment with throttling if that happens.
if (!url_request.url().SchemeIsHTTPOrHTTPS())
return START_REQUEST;
if (params_for_network_quality_.max_queuing_time &&
tick_clock_->NowTicks() - url_request.creation_time() >=
params_for_network_quality_.max_queuing_time) {
return START_REQUEST;
}
const net::HostPortPair& host_port_pair = request->host_port_pair();
bool priority_delayable =
params_for_network_quality_.delay_requests_on_multiplexed_connections;
url::SchemeHostPort scheme_host_port(url_request.url());
bool supports_priority =
url_request.context()
->http_server_properties()
->SupportsRequestPriority(scheme_host_port,
url_request.network_isolation_key());
if (!priority_delayable) {
// TODO(willchan): We should really improve this algorithm as described in
// https://crbug.com/164101. Also, theoretically we should not count a
// request-priority capable request against the delayable requests limit.
if (supports_priority)
return START_REQUEST;
}
// Non-delayable requests.
if (!RequestAttributesAreSet(request->attributes(), kAttributeDelayable))
return START_REQUEST;
// Delayable requests.
DCHECK_GE(in_flight_requests_.size(), in_flight_delayable_count_);
size_t num_non_delayable_requests_weighted = static_cast<size_t>(
params_for_network_quality_.non_delayable_weight *
(in_flight_requests_.size() - in_flight_delayable_count_));
if ((in_flight_delayable_count_ + num_non_delayable_requests_weighted >=
params_for_network_quality_.max_delayable_requests)) {
return DO_NOT_START_REQUEST_AND_STOP_SEARCHING;
}
if (ReachedMaxRequestsPerHostPerClient(host_port_pair, supports_priority)) {
// There may be other requests for other hosts that may be allowed,
// so keep checking.
return DO_NOT_START_REQUEST_AND_KEEP_SEARCHING;
}
// The in-flight requests consist of layout-blocking requests,
// normal requests and delayable requests. Everything except for
// delayable requests is handled above here so this is deciding what to
// do with a delayable request while we are in the layout-blocking phase
// of loading.
if (total_layout_blocking_count_ != 0) {
size_t non_delayable_requests_in_flight_count =
in_flight_requests_.size() - in_flight_delayable_count_;
if (non_delayable_requests_in_flight_count >
kInFlightNonDelayableRequestCountPerClientThreshold) {
// Too many higher priority in-flight requests to allow lower priority
// requests through.
return DO_NOT_START_REQUEST_AND_STOP_SEARCHING;
}
if (in_flight_requests_.size() > 0 &&
(in_flight_delayable_count_ >=
kMaxNumDelayableWhileLayoutBlockingPerClient)) {
// Block the request if at least one request is in flight and the
// number of in-flight delayable requests has hit the configured
// limit.
return DO_NOT_START_REQUEST_AND_STOP_SEARCHING;
}
}
if (IsNonDelayableRequestAnticipated()) {
return DO_NOT_START_REQUEST_AND_STOP_SEARCHING;
}
return START_REQUEST;
}
// Returns true if a non-delayable request is expected to arrive soon.
bool IsNonDelayableRequestAnticipated() const {
base::Optional<double> http_rtt_multiplier =
params_for_network_quality_
.http_rtt_multiplier_for_proactive_throttling;
if (!http_rtt_multiplier.has_value())
return false;
if (http_rtt_multiplier <= 0)
return false;
// Currently, the heuristic for predicting the arrival of a non-delayable
// request makes a prediction only if a non-delayable request has started
// previously in this resource scheduler client.
if (!last_non_delayable_request_start_.has_value())
return false;
base::Optional<base::TimeDelta> http_rtt =
network_quality_estimator_->GetHttpRTT();
if (!http_rtt.has_value())
return false;
base::TimeDelta threshold_for_proactive_throttling =
http_rtt.value() * http_rtt_multiplier.value();
base::TimeDelta time_since_last_non_delayable_request_start =
tick_clock_->NowTicks() - last_non_delayable_request_start_.value();
if (time_since_last_non_delayable_request_start >=
threshold_for_proactive_throttling) {
// Last non-delayable request started more than
// |threshold_for_proactive_throttling| back. The algorithm estimates that
// by this time any non-delayable that were triggered by requests that
// started long time back would have arrived at resource scheduler by now.
//
// On the other hand, if the last non-delayable request started recently,
// then it's likely that the parsing of the response from that recently
// started request would trigger additional non-delayable requests.
return false;
}
return true;
}
// It is common for a burst of messages to come from the renderer which
// trigger starting pending requests. Naively, this would result in O(n*m)
// behavior for n pending requests and m <= n messages, as
// LoadAnyStartablePendingRequest is O(n) for n pending requests. To solve
// this, just post a task to the end of the queue to call the method,
// coalescing the m messages into a single call to
// LoadAnyStartablePendingRequests.
// TODO(csharrison): Reconsider this if IPC batching becomes an easy to use
// pattern.
void ScheduleLoadAnyStartablePendingRequests(RequestStartTrigger trigger) {
if (num_skipped_scans_due_to_scheduled_start_ == 0) {
TRACE_EVENT0("loading", "ScheduleLoadAnyStartablePendingRequests");
resource_scheduler_->task_runner()->PostTask(
FROM_HERE, base::BindOnce(&Client::LoadAnyStartablePendingRequests,
weak_ptr_factory_.GetWeakPtr(), trigger));
}
num_skipped_scans_due_to_scheduled_start_ += 1;
}
void LoadAnyStartablePendingRequests(RequestStartTrigger trigger) {
// We iterate through all the pending requests, starting with the highest
// priority one. For each entry, one of three things can happen:
// 1) We start the request, remove it from the list, and keep checking.
// 2) We do NOT start the request, but ShouldStartRequest() signals us that
// there may be room for other requests, so we keep checking and leave
// the previous request still in the list.
// 3) We do not start the request, same as above, but StartRequest() tells
// us there's no point in checking any further requests.
TRACE_EVENT0("loading", "LoadAnyStartablePendingRequests");
if (num_skipped_scans_due_to_scheduled_start_ > 0) {
UMA_HISTOGRAM_COUNTS_1M("ResourceScheduler.NumSkippedScans.ScheduleStart",
num_skipped_scans_due_to_scheduled_start_);
}
num_skipped_scans_due_to_scheduled_start_ = 0;
RequestQueue::NetQueue::iterator request_iter =
pending_requests_.GetNextHighestIterator();
while (request_iter != pending_requests_.End()) {
ScheduledResourceRequestImpl* request = *request_iter;
ShouldStartReqResult query_result = ShouldStartRequest(request);
if (query_result == START_REQUEST) {
pending_requests_.Erase(request);
StartRequest(request, START_ASYNC, trigger);
// StartRequest can modify the pending list, so we (re)start evaluation
// from the currently highest priority request. Avoid copying a singular
// iterator, which would trigger undefined behavior.
if (pending_requests_.GetNextHighestIterator() ==
pending_requests_.End())
break;
request_iter = pending_requests_.GetNextHighestIterator();
} else if (query_result == DO_NOT_START_REQUEST_AND_KEEP_SEARCHING) {
++request_iter;
continue;
} else {
DCHECK(query_result == DO_NOT_START_REQUEST_AND_STOP_SEARCHING);
break;
}
}
}
// If |request| was delayable, this method records how long after |request|
// started, a non-delayable request also started. This is the duration of time
// that |request| should have been queued for so as to avoid any network
// contention with all later-arriving non-delayable requests. Must be called
// after |request| is finished.
void RecordNetworkContentionMetrics(
const ScheduledResourceRequestImpl& request) const {
if (!RequestAttributesAreSet(request.attributes(), kAttributeDelayable))
return;
base::TimeDelta ideal_duration_to_wait;
if (!last_non_delayable_request_start_) {
// No non-delayable request has been started in this client so far.
// |request| did not have to wait at all to avoid network contention.
ideal_duration_to_wait = base::TimeDelta();
} else if (request.url_request()->creation_time() >
last_non_delayable_request_start_) {
// Last non-delayable request in this client started before |request|
// was created. |request| did not have to wait at all to avoid network
// contention with non-delayable requests.
ideal_duration_to_wait = base::TimeDelta();
} else {
// The latest non-delayable request started at
// |last_non_delayable_request_start_| which happened after the
// creation of |request|.
ideal_duration_to_wait = last_non_delayable_request_start_.value() -
request.url_request()->creation_time();
}
UMA_HISTOGRAM_MEDIUM_TIMES(
"ResourceScheduler.DelayableRequests."
"WaitTimeToAvoidContentionWithNonDelayableRequest",
ideal_duration_to_wait);
}
// Tracks if the main HTML parser has reached the body which marks the end of
// layout-blocking resources.
// This is disabled and the is always true when kRendererSideResourceScheduler
// is enabled.
RequestQueue pending_requests_;
RequestSet in_flight_requests_;
// True if |this| client is created for browser initiated requests.
const bool is_browser_client_;
// The number of delayable in-flight requests.
size_t in_flight_delayable_count_;
// The number of layout-blocking in-flight requests.
size_t total_layout_blocking_count_;
// The number of LoadAnyStartablePendingRequests scans that were skipped due
// to smarter task scheduling around reprioritization.
int num_skipped_scans_due_to_scheduled_start_;
// Network quality estimator for network aware resource scheudling. This may
// be null.
net::NetworkQualityEstimator* network_quality_estimator_;
// Resource scheduling params computed for the current network quality.
// These are recomputed every time an |OnNavigate| event is triggered.
ResourceSchedulerParamsManager::ParamsForNetworkQuality
params_for_network_quality_;
// A pointer to the resource scheduler which contains the resource scheduling
// configuration.
ResourceScheduler* resource_scheduler_;
// Guaranteed to be non-null.
const base::TickClock* tick_clock_;
// Time when the last non-delayble request started in this client.
base::Optional<base::TimeTicks> last_non_delayable_request_start_;
// Time when the last non-delayble request ended in this client.
base::Optional<base::TimeTicks> last_non_delayable_request_end_;
// Current estimated value of the effective connection type.
net::EffectiveConnectionType effective_connection_type_ =
net::EFFECTIVE_CONNECTION_TYPE_UNKNOWN;
// Current count of active peer to peer connections.
uint32_t p2p_connections_count_ = 0u;
// Earliest timestamp since when there is at least one active peer to peer
// connection. Set to current timestamp when |p2p_connections_count_|
// changes from 0 to a non-zero value. Reset to null when
// |p2p_connections_count_| becomes 0.
base::Optional<base::TimeTicks> p2p_connections_count_active_timestamp_;
// Earliest timestamp since when the count of active peer to peer
// connection counts dropped from a non-zero value to zero. Set to current
// timestamp when |p2p_connections_count_| changes from a non-zero value to 0.
base::Optional<base::TimeTicks> p2p_connections_count_end_timestamp_;
base::OneShotTimer p2p_connections_count_ended_timer_;
SEQUENCE_CHECKER(sequence_checker_);
base::WeakPtrFactory<ResourceScheduler::Client> weak_ptr_factory_{this};
};
ResourceScheduler::ResourceScheduler(bool enabled,
const base::TickClock* tick_clock)
: tick_clock_(tick_clock ? tick_clock
: base::DefaultTickClock::GetInstance()),
enabled_(enabled),
queued_requests_dispatch_periodicity_(
GetQueuedRequestsDispatchPeriodicity()),
task_runner_(base::ThreadTaskRunnerHandle::Get()) {
DCHECK(tick_clock_);
StartLongQueuedRequestsDispatchTimerIfNeeded();
}
ResourceScheduler::~ResourceScheduler() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
DCHECK(unowned_requests_.empty());
DCHECK(client_map_.empty());
}
std::unique_ptr<ResourceScheduler::ScheduledResourceRequest>
ResourceScheduler::ScheduleRequest(int child_id,
int route_id,
bool is_async,
net::URLRequest* url_request) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
ClientId client_id = MakeClientId(child_id, route_id);
std::unique_ptr<ScheduledResourceRequestImpl> request(
new ScheduledResourceRequestImpl(
client_id, url_request, this,
RequestPriorityParams(url_request->priority(), 0), is_async));
ClientMap::iterator it = client_map_.find(client_id);
if (it == client_map_.end()) {
// There are several ways this could happen:
// 1. <a ping> requests don't have a route_id.
// 2. Most unittests don't send the IPCs needed to register Clients.
// 3. The tab is closed while a RequestResource IPC is in flight.
unowned_requests_.insert(request.get());
request->Start(START_SYNC);
return std::move(request);
}
Client* client = it->second.get();
client->ScheduleRequest(*url_request, request.get());
if (!IsLongQueuedRequestsDispatchTimerRunning())
StartLongQueuedRequestsDispatchTimerIfNeeded();
return std::move(request);
}
void ResourceScheduler::RemoveRequest(ScheduledResourceRequestImpl* request) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
if (base::Contains(unowned_requests_, request)) {
unowned_requests_.erase(request);
return;
}
ClientMap::iterator client_it = client_map_.find(request->client_id());
if (client_it == client_map_.end())
return;
Client* client = client_it->second.get();
client->RemoveRequest(request);
}
void ResourceScheduler::OnClientCreated(
int child_id,
int route_id,
net::NetworkQualityEstimator* network_quality_estimator) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
ClientId client_id = MakeClientId(child_id, route_id);
DCHECK(!base::Contains(client_map_, client_id));
client_map_[client_id] =
std::make_unique<Client>(child_id == mojom::kBrowserProcessId,
network_quality_estimator, this, tick_clock_);
UMA_HISTOGRAM_COUNTS_100("ResourceScheduler.ActiveSchedulerClientsCount",
ActiveSchedulerClientsCounter());
}
void ResourceScheduler::OnClientDeleted(int child_id, int route_id) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
ClientId client_id = MakeClientId(child_id, route_id);
ClientMap::iterator it = client_map_.find(client_id);
// TODO(crbug.com/873959): Turns this CHECK to DCHECK once the investigation
// is done.
CHECK(it != client_map_.end());
Client* client = it->second.get();
// TODO(crbug.com/873959): Remove this CHECK once the investigation is done.
CHECK(client);
DCHECK(client->HasNoPendingRequests() ||
IsLongQueuedRequestsDispatchTimerRunning());
// ResourceDispatcherHost cancels all requests except for cross-renderer
// navigations, async revalidations and detachable requests after
// OnClientDeleted() returns.
RequestSet client_unowned_requests = client->StartAndRemoveAllRequests();
for (RequestSet::iterator request_it = client_unowned_requests.begin();
request_it != client_unowned_requests.end(); ++request_it) {
unowned_requests_.insert(*request_it);
}
client_map_.erase(it);
}
size_t ResourceScheduler::ActiveSchedulerClientsCounter() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
size_t active_scheduler_clients_count = 0;
for (const auto& client : client_map_) {
if (client.second->IsActiveResourceSchedulerClient()) {
++active_scheduler_clients_count;
}
}
return active_scheduler_clients_count;
}
// Records the metrics related to number of requests in flight that are observed
// by the global resource scheduler.
void ResourceScheduler::RecordGlobalRequestCountMetrics() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
size_t global_delayable_count = 0;
size_t global_non_delayable_count = 0;
size_t global_layout_blocking_count = 0;
for (const auto& client : client_map_) {
global_delayable_count += client.second->CountInflightDelayableRequests();
global_non_delayable_count +=
client.second->CountInflightNonDelayableRequests();
global_layout_blocking_count +=
client.second->CountInflightLayoutBlockingRequests();
}
UMA_HISTOGRAM_COUNTS_100("ResourceScheduler.RequestsCount.GlobalAll",
global_delayable_count + global_non_delayable_count);
UMA_HISTOGRAM_COUNTS_100("ResourceScheduler.RequestsCount.GlobalDelayable",
global_delayable_count);
UMA_HISTOGRAM_COUNTS_100("ResourceScheduler.RequestsCount.GlobalNonDelayable",
global_non_delayable_count);
UMA_HISTOGRAM_COUNTS_100(
"ResourceScheduler.RequestsCount.GlobalLayoutBlocking",
global_layout_blocking_count);
}
ResourceScheduler::Client* ResourceScheduler::GetClient(int child_id,
int route_id) {
ClientId client_id = MakeClientId(child_id, route_id);
ClientMap::iterator client_it = client_map_.find(client_id);
if (client_it == client_map_.end())
return nullptr;
return client_it->second.get();
}
void ResourceScheduler::StartLongQueuedRequestsDispatchTimerIfNeeded() {
bool pending_request_found = false;
for (const auto& client : client_map_) {
if (!client.second->HasNoPendingRequests()) {
pending_request_found = true;
break;
}
}
// If there are no pending requests, then do not start the timer. This ensures
// that we are not running the periodic timer when Chrome is not being
// actively used (e.g., it's in background).
if (!pending_request_found)
return;
long_queued_requests_dispatch_timer_.Start(
FROM_HERE, queued_requests_dispatch_periodicity_, this,
&ResourceScheduler::OnLongQueuedRequestsDispatchTimerFired);
}
void ResourceScheduler::OnLongQueuedRequestsDispatchTimerFired() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
for (auto& client : client_map_)
client.second->OnLongQueuedRequestsDispatchTimerFired();
StartLongQueuedRequestsDispatchTimerIfNeeded();
}
void ResourceScheduler::ReprioritizeRequest(net::URLRequest* request,
net::RequestPriority new_priority,
int new_intra_priority_value) {
if (request->load_flags() & net::LOAD_IGNORE_LIMITS) {
// Requests with the IGNORE_LIMITS flag must stay at MAXIMUM_PRIORITY.
return;
}
auto* scheduled_resource_request =
ScheduledResourceRequestImpl::ForRequest(request);
// Downloads don't use the resource scheduler.
if (!scheduled_resource_request) {
request->SetPriority(new_priority);
return;
}
RequestPriorityParams new_priority_params(new_priority,
new_intra_priority_value);
RequestPriorityParams old_priority_params =
scheduled_resource_request->get_request_priority_params();
if (old_priority_params == new_priority_params)
return;
ClientMap::iterator client_it =
client_map_.find(scheduled_resource_request->client_id());
if (client_it == client_map_.end()) {
// The client was likely deleted shortly before we received this IPC.
request->SetPriority(new_priority_params.priority);
scheduled_resource_request->set_request_priority_params(
new_priority_params);
return;
}
Client* client = client_it->second.get();
client->ReprioritizeRequest(scheduled_resource_request, old_priority_params,
new_priority_params);
}
void ResourceScheduler::ReprioritizeRequest(net::URLRequest* request,
net::RequestPriority new_priority) {
int current_intra_priority = 0;
auto* existing_request = ScheduledResourceRequestImpl::ForRequest(request);
if (existing_request) {
current_intra_priority =
existing_request->get_request_priority_params().intra_priority;
}
ReprioritizeRequest(request, new_priority, current_intra_priority);
}
ResourceScheduler::ClientId ResourceScheduler::MakeClientId(
int child_id,
int route_id) const {
return (static_cast<ResourceScheduler::ClientId>(child_id) << 32) | route_id;
}
bool ResourceScheduler::IsLongQueuedRequestsDispatchTimerRunning() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
return long_queued_requests_dispatch_timer_.IsRunning();
}
void ResourceScheduler::SetResourceSchedulerParamsManagerForTests(
const ResourceSchedulerParamsManager& resource_scheduler_params_manager) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
resource_scheduler_params_manager_.Reset(resource_scheduler_params_manager);
for (const auto& pair : client_map_) {
pair.second->UpdateParamsForNetworkQuality();
}
}
void ResourceScheduler::DispatchLongQueuedRequestsForTesting() {
long_queued_requests_dispatch_timer_.Stop();
OnLongQueuedRequestsDispatchTimerFired();
}
} // namespace network