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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#include "singleexecutor.h"
#include <vespa/vespalib/util/alloc.h>
#include <cassert>
namespace vespalib {
SingleExecutor::SingleExecutor(init_fun_t func, uint32_t reservedQueueSize, bool isQueueSizeHard, uint32_t watermark, duration reactionTime)
: _watermarkRatio(watermark < reservedQueueSize ? double(watermark) / reservedQueueSize : 1.0),
_taskLimit(vespalib::roundUp2inN(reservedQueueSize)),
_wantedTaskLimit(_taskLimit.load()),
_rp(0),
_tasks(std::make_unique<Task::UP[]>(_taskLimit)),
_mutex(),
_consumerCondition(),
_producerCondition(),
_thread(),
_stopped(false),
_idleTracker(steady_clock::now()),
_threadIdleTracker(),
_wakeupCount(0),
_lastAccepted(0),
_queueSize(),
_wakeupConsumerAt(0),
_producerNeedWakeupAt(0),
_wp(0),
_watermark(_taskLimit.load()*_watermarkRatio),
_reactionTime(reactionTime),
_closed(false),
_overflow()
{
assert(reservedQueueSize >= watermark);
if ( ! isQueueSizeHard) {
_overflow = std::make_unique<ArrayQueue<Task::UP>>();
}
_thread = thread::start(*this, func);
}
SingleExecutor::~SingleExecutor() {
shutdown();
sync();
stop();
_consumerCondition.notify_one();
_thread.join();
}
size_t
SingleExecutor::getNumThreads() const {
return 1;
}
void
SingleExecutor::sleepProducer(Lock & lock, duration maxWaitTime, uint64_t wakeupAt) {
_producerNeedWakeupAt.store(wakeupAt, std::memory_order_relaxed);
_producerCondition.wait_for(lock, maxWaitTime);
_producerNeedWakeupAt.store(0, std::memory_order_relaxed);
}
Executor::Task::UP
SingleExecutor::execute(Task::UP task) {
uint64_t wp;
{
Lock guard(_mutex);
if (_closed) {
return task;
}
task = wait_for_room_or_put_in_overflow_Q(guard, std::move(task));
if (task) {
wp = move_to_main_q(guard, std::move(task));
} else {
wp = _wp.load(std::memory_order_relaxed) + num_tasks_in_overflow_q(guard);
}
}
if (wp == _wakeupConsumerAt.load(std::memory_order_relaxed)) {
_consumerCondition.notify_one();
}
return task;
}
uint64_t
SingleExecutor::numTasks() {
if (_overflow) {
Lock guard(_mutex);
return num_tasks_in_main_q() + num_tasks_in_overflow_q(guard);
} else {
return num_tasks_in_main_q();
}
}
uint64_t
SingleExecutor::move_to_main_q(Lock &, Task::UP task) {
uint64_t wp = _wp.load(std::memory_order_relaxed);
_tasks[index(wp)] = std::move(task);
_wp.store(wp + 1, std::memory_order_release);
return wp;
}
void
SingleExecutor::setTaskLimit(uint32_t taskLimit) {
_wantedTaskLimit = vespalib::roundUp2inN(taskLimit);
}
void
SingleExecutor::drain(Lock & lock) {
uint64_t wp = _wp.load(std::memory_order_relaxed);
while (numTasks(lock) > 0) {
_consumerCondition.notify_one();
sleepProducer(lock, 100us, wp);
}
}
void
SingleExecutor::wakeup() {
if (numTasks() > 0) {
_consumerCondition.notify_one();
}
}
SingleExecutor &
SingleExecutor::sync() {
Lock lock(_mutex);
uint64_t wp = _wp.load(std::memory_order_relaxed) + num_tasks_in_overflow_q(lock);
while (wp > _rp.load(std::memory_order_acquire)) {
_consumerCondition.notify_one();
sleepProducer(lock, 100us, wp);
}
return *this;
}
SingleExecutor &
SingleExecutor::shutdown() {
Lock lock(_mutex);
_closed = true;
return *this;
}
void
SingleExecutor::run() {
while (!stopped()) {
drain_tasks();
_producerCondition.notify_all();
_wakeupConsumerAt.store(_wp.load(std::memory_order_relaxed) + get_watermark(), std::memory_order_relaxed);
Lock lock(_mutex);
if (numTasks(lock) <= 0) {
steady_time now = steady_clock::now();
_threadIdleTracker.set_idle(now);
_consumerCondition.wait_until(lock, now + _reactionTime);
_idleTracker.was_idle(_threadIdleTracker.set_active(steady_clock::now()));
_wakeupCount++;
}
_wakeupConsumerAt.store(0, std::memory_order_relaxed);
}
}
void
SingleExecutor::drain_tasks() {
while (numTasks() > 0) {
run_tasks_till(_wp.load(std::memory_order_acquire));
move_overflow_to_main_q();
}
}
void
SingleExecutor::move_overflow_to_main_q()
{
if ( ! _overflow) return;
Lock guard(_mutex);
move_overflow_to_main_q(guard);
}
void
SingleExecutor::move_overflow_to_main_q(Lock & guard) {
while ( !_overflow->empty() && num_tasks_in_main_q() < _taskLimit.load(std::memory_order_relaxed)) {
move_to_main_q(guard, std::move(_overflow->front()));
_overflow->pop();
}
}
void
SingleExecutor::run_tasks_till(uint64_t available) {
uint64_t consumed = _rp.load(std::memory_order_relaxed);
uint64_t wakeupLimit = _producerNeedWakeupAt.load(std::memory_order_relaxed);
while (consumed < available) {
Task::UP task = std::move(_tasks[index(consumed)]);
task->run();
_rp.store(++consumed, std::memory_order_release);
if (wakeupLimit == consumed) {
_producerCondition.notify_all();
}
}
}
Executor::Task::UP
SingleExecutor::wait_for_room_or_put_in_overflow_Q(Lock & guard, Task::UP task) {
uint64_t wp = _wp.load(std::memory_order_relaxed);
uint64_t taskLimit = _taskLimit.load(std::memory_order_relaxed);
if (taskLimit != _wantedTaskLimit.load(std::memory_order_relaxed)) {
drain(guard);
_tasks = std::make_unique<Task::UP[]>(_wantedTaskLimit);
_taskLimit = _wantedTaskLimit.load();
_watermark = _taskLimit * _watermarkRatio;
}
uint64_t numTaskInQ = numTasks(guard);
_queueSize.add(numTaskInQ);
if (numTaskInQ >= _taskLimit.load(std::memory_order_relaxed)) {
if (_overflow) {
_overflow->push(std::move(task));
} else {
while (numTasks(guard) >= _taskLimit.load(std::memory_order_relaxed)) {
sleepProducer(guard, _reactionTime, wp - get_watermark());
}
}
} else {
if (_overflow && !_overflow->empty()) {
_overflow->push(std::move(task));
}
}
if (_overflow && !_overflow->empty()) {
assert(!task);
move_overflow_to_main_q(guard);
}
return task;
}
ExecutorStats
SingleExecutor::getStats() {
Lock lock(_mutex);
uint64_t accepted = _wp.load(std::memory_order_relaxed) + num_tasks_in_overflow_q(lock);
steady_time now = steady_clock::now();
_idleTracker.was_idle(_threadIdleTracker.reset(now));
ExecutorStats stats(_queueSize, (accepted - _lastAccepted), 0, _wakeupCount);
stats.setUtil(1, _idleTracker.reset(now, 1));
_wakeupCount = 0;
_lastAccepted = accepted;
_queueSize = ExecutorStats::QueueSizeT() ;
return stats;
}
}
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