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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "net/base/prioritized_dispatcher.h"
#include <ostream>
#include "base/check_op.h"
namespace net {
PrioritizedDispatcher::Limits::Limits(Priority num_priorities,
size_t total_jobs)
: total_jobs(total_jobs), reserved_slots(num_priorities) {}
PrioritizedDispatcher::Limits::Limits(const Limits& other) = default;
PrioritizedDispatcher::Limits::~Limits() = default;
PrioritizedDispatcher::PrioritizedDispatcher(const Limits& limits)
: queue_(limits.reserved_slots.size()),
max_running_jobs_(limits.reserved_slots.size()) {
SetLimits(limits);
}
PrioritizedDispatcher::~PrioritizedDispatcher() = default;
PrioritizedDispatcher::Handle PrioritizedDispatcher::Add(
Job* job, Priority priority) {
DCHECK(job);
DCHECK_LT(priority, num_priorities());
if (num_running_jobs_ < max_running_jobs_[priority]) {
++num_running_jobs_;
job->Start();
return Handle();
}
return queue_.Insert(job, priority);
}
PrioritizedDispatcher::Handle PrioritizedDispatcher::AddAtHead(
Job* job, Priority priority) {
DCHECK(job);
DCHECK_LT(priority, num_priorities());
if (num_running_jobs_ < max_running_jobs_[priority]) {
++num_running_jobs_;
job->Start();
return Handle();
}
return queue_.InsertAtFront(job, priority);
}
void PrioritizedDispatcher::Cancel(const Handle& handle) {
queue_.Erase(handle);
}
PrioritizedDispatcher::Job* PrioritizedDispatcher::EvictOldestLowest() {
Handle handle = queue_.FirstMin();
if (handle.is_null())
return nullptr;
Job* job = handle.value();
Cancel(handle);
return job;
}
PrioritizedDispatcher::Handle PrioritizedDispatcher::ChangePriority(
const Handle& handle, Priority priority) {
DCHECK(!handle.is_null());
DCHECK_LT(priority, num_priorities());
DCHECK_GE(num_running_jobs_, max_running_jobs_[handle.priority()]) <<
"Job should not be in queue when limits permit it to start.";
if (handle.priority() == priority)
return handle;
if (MaybeDispatchJob(handle, priority))
return Handle();
Job* job = handle.value();
queue_.Erase(handle);
return queue_.Insert(job, priority);
}
void PrioritizedDispatcher::OnJobFinished() {
DCHECK_GT(num_running_jobs_, 0u);
--num_running_jobs_;
MaybeDispatchNextJob();
}
PrioritizedDispatcher::Limits PrioritizedDispatcher::GetLimits() const {
size_t num_priorities = max_running_jobs_.size();
Limits limits(num_priorities, max_running_jobs_.back());
// Calculate the number of jobs reserved for each priority and higher. Leave
// the number of jobs reserved for the lowest priority or higher as 0.
for (size_t i = 1; i < num_priorities; ++i) {
limits.reserved_slots[i] = max_running_jobs_[i] - max_running_jobs_[i - 1];
}
return limits;
}
void PrioritizedDispatcher::SetLimits(const Limits& limits) {
DCHECK_EQ(queue_.num_priorities(), limits.reserved_slots.size());
size_t total = 0;
for (size_t i = 0; i < limits.reserved_slots.size(); ++i) {
total += limits.reserved_slots[i];
max_running_jobs_[i] = total;
}
// Unreserved slots are available for all priorities.
DCHECK_LE(total, limits.total_jobs) << "sum(reserved_slots) <= total_jobs";
size_t spare = limits.total_jobs - total;
for (size_t i = limits.reserved_slots.size(); i > 0; --i) {
max_running_jobs_[i - 1] += spare;
}
// Start pending jobs, if limits permit.
while (true) {
if (!MaybeDispatchNextJob())
break;
}
}
void PrioritizedDispatcher::SetLimitsToZero() {
SetLimits(Limits(queue_.num_priorities(), 0));
}
bool PrioritizedDispatcher::MaybeDispatchJob(const Handle& handle,
Priority job_priority) {
DCHECK_LT(job_priority, num_priorities());
if (num_running_jobs_ >= max_running_jobs_[job_priority])
return false;
Job* job = handle.value();
queue_.Erase(handle);
++num_running_jobs_;
job->Start();
return true;
}
bool PrioritizedDispatcher::MaybeDispatchNextJob() {
Handle handle = queue_.FirstMax();
if (handle.is_null()) {
DCHECK_EQ(0u, queue_.size());
return false;
}
return MaybeDispatchJob(handle, handle.priority());
}
} // namespace net
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