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// Copyright 2015 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 "content/renderer/scheduler/resource_dispatch_throttler.h"
#include "base/auto_reset.h"
#include "base/trace_event/trace_event.h"
#include "components/scheduler/renderer/renderer_scheduler.h"
#include "content/common/resource_messages.h"
#include "ipc/ipc_message_macros.h"
namespace content {
namespace {
bool IsResourceRequest(const IPC::Message& msg) {
return msg.type() == ResourceHostMsg_RequestResource::ID;
}
} // namespace
ResourceDispatchThrottler::ResourceDispatchThrottler(
IPC::Sender* proxied_sender,
scheduler::RendererScheduler* scheduler,
base::TimeDelta flush_period,
uint32_t max_requests_per_flush)
: proxied_sender_(proxied_sender),
scheduler_(scheduler),
flush_period_(flush_period),
max_requests_per_flush_(max_requests_per_flush),
flush_timer_(
FROM_HERE,
flush_period_,
base::Bind(&ResourceDispatchThrottler::Flush, base::Unretained(this)),
false /* is_repeating */),
sent_requests_since_last_flush_(0) {
DCHECK(proxied_sender);
DCHECK(scheduler);
DCHECK_NE(flush_period_, base::TimeDelta());
DCHECK(max_requests_per_flush_);
flush_timer_.SetTaskRunner(scheduler->LoadingTaskRunner());
}
ResourceDispatchThrottler::~ResourceDispatchThrottler() {
FlushAll();
}
bool ResourceDispatchThrottler::Send(IPC::Message* msg) {
DCHECK(thread_checker_.CalledOnValidThread());
if (msg->is_sync()) {
// Flush any pending requests, preserving dispatch order between async and
// sync requests.
FlushAll();
return ForwardMessage(msg);
}
// Always defer message forwarding if there are pending messages, ensuring
// message dispatch ordering consistency.
if (!throttled_messages_.empty()) {
TRACE_EVENT_INSTANT0("loader", "ResourceDispatchThrottler::ThrottleMessage",
TRACE_EVENT_SCOPE_THREAD);
throttled_messages_.push_back(msg);
return true;
}
if (!IsResourceRequest(*msg))
return ForwardMessage(msg);
if (!scheduler_->IsHighPriorityWorkAnticipated())
return ForwardMessage(msg);
if (Now() > (last_sent_request_time_ + flush_period_)) {
// If sufficient time has passed since the previous send, we can effectively
// mark the pipeline as flushed.
sent_requests_since_last_flush_ = 0;
return ForwardMessage(msg);
}
if (sent_requests_since_last_flush_ < max_requests_per_flush_)
return ForwardMessage(msg);
TRACE_EVENT_INSTANT0("loader", "ResourceDispatchThrottler::ThrottleRequest",
TRACE_EVENT_SCOPE_THREAD);
throttled_messages_.push_back(msg);
ScheduleFlush();
return true;
}
base::TimeTicks ResourceDispatchThrottler::Now() const {
return base::TimeTicks::Now();
}
void ResourceDispatchThrottler::ScheduleFlush() {
DCHECK(!flush_timer_.IsRunning());
flush_timer_.Reset();
}
void ResourceDispatchThrottler::Flush() {
DCHECK(thread_checker_.CalledOnValidThread());
TRACE_EVENT1("loader", "ResourceDispatchThrottler::Flush",
"total_throttled_messages", throttled_messages_.size());
sent_requests_since_last_flush_ = 0;
// If high-priority work is no longer anticipated, dispatch can be safely
// accelerated. Avoid completely flushing in such case in the event that
// a large number of requests have been throttled.
uint32_t max_requests = scheduler_->IsHighPriorityWorkAnticipated()
? max_requests_per_flush_
: max_requests_per_flush_ * 2;
while (!throttled_messages_.empty() &&
(sent_requests_since_last_flush_ < max_requests ||
!IsResourceRequest(*throttled_messages_.front()))) {
IPC::Message* msg = throttled_messages_.front();
throttled_messages_.pop_front();
ForwardMessage(msg);
}
if (!throttled_messages_.empty())
ScheduleFlush();
}
void ResourceDispatchThrottler::FlushAll() {
if (throttled_messages_.empty())
return;
TRACE_EVENT1("loader", "ResourceDispatchThrottler::FlushAll",
"total_throttled_messages", throttled_messages_.size());
std::deque<IPC::Message*> throttled_messages;
throttled_messages.swap(throttled_messages_);
for (auto& message : throttled_messages)
ForwardMessage(message);
// There shouldn't be re-entrancy issues when forwarding an IPC, but validate
// as a safeguard.
DCHECK(throttled_messages_.empty());
}
bool ResourceDispatchThrottler::ForwardMessage(IPC::Message* msg) {
if (IsResourceRequest(*msg)) {
last_sent_request_time_ = Now();
++sent_requests_since_last_flush_;
}
return proxied_sender_->Send(msg);
}
} // namespace content
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