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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include "count_down_latch.h"
#include "thread.h"
#include "runnable.h"
#include "thread_bundle.h"
namespace vespalib {
namespace fixed_thread_bundle {
/**
* collection of work to be done by a single call to the thread bundle
* run function, and latch to count down when each part is done. The
* same data structure will be reused for all calls to run in order to
* support static wiring of signal paths and execution hooks.
**/
struct Work {
Runnable* const* targets;
size_t cnt;
CountDownLatch *latch;
Work() : targets(nullptr), cnt(0), latch(nullptr) {}
};
/**
* the subset of work to be done by a single thread.
**/
struct Part {
const Work &work;
size_t offset;
Part(const Work &w, size_t o) : work(w), offset(o) {}
bool valid() const noexcept { return (offset < work.cnt); }
void perform() {
if (valid()) {
work.targets[offset]->run();
}
work.latch->countDown();
}
};
/**
* countable signal path between threads.
**/
struct Signal {
bool valid;
size_t generation;
std::unique_ptr<std::mutex> monitor;
std::unique_ptr<std::condition_variable> cond;
Signal() noexcept;
Signal(Signal &&) noexcept = default;
~Signal();
size_t wait(size_t &localGen) const {
std::unique_lock guard(*monitor);
while (localGen == generation) {
cond->wait(guard);
}
size_t diff = (generation - localGen);
localGen = generation;
return (valid ? diff : 0);
}
void send() {
std::lock_guard guard(*monitor);
++generation;
cond->notify_one();
}
void broadcast() {
std::lock_guard guard(*monitor);
++generation;
cond->notify_all();
}
void cancel() {
std::lock_guard guard(*monitor);
++generation;
valid = false;
cond->notify_all();
}
};
} // namespace vespalib::fixed_thread_bundle
/**
* A ThreadBundle implementation employing a fixed set of internal
* threads. The internal Pool class can be used to recycle bundles.
**/
class SimpleThreadBundle : public ThreadBundle
{
public:
using Work = fixed_thread_bundle::Work;
using Signal = fixed_thread_bundle::Signal;
using init_fun_t = Runnable::init_fun_t;
using UP = std::unique_ptr<SimpleThreadBundle>;
enum Strategy { USE_SIGNAL_LIST, USE_SIGNAL_TREE, USE_BROADCAST };
class Pool
{
private:
std::mutex _lock;
size_t _bundleSize;
init_fun_t _init_fun;
std::vector<SimpleThreadBundle*> _bundles;
public:
class Guard {
public:
explicit Guard(Pool & pool) : _bundle(pool.obtain()), _pool(pool) {}
Guard(const Guard &) = delete;
Guard & operator =(const Guard &) = delete;
~Guard() { _pool.release(std::move(_bundle)); }
SimpleThreadBundle & bundle() { return *_bundle; }
private:
SimpleThreadBundle::UP _bundle;
Pool &_pool;
};
Pool(size_t bundleSize, init_fun_t init_fun);
explicit Pool(size_t bundleSize) : Pool(bundleSize, Runnable::default_init_function) {}
~Pool();
Guard getBundle() { return Guard(*this); }
//TODO Make private
SimpleThreadBundle::UP obtain();
void release(SimpleThreadBundle::UP bundle);
};
private:
struct Worker : Runnable {
using UP = std::unique_ptr<Worker>;
std::thread thread;
Signal &signal;
Runnable::UP hook;
Worker(Signal &s, init_fun_t init_fun, Runnable::UP h);
void run() override;
};
Work _work;
std::vector<Signal> _signals;
std::vector<Worker::UP> _workers;
Runnable::UP _hook;
public:
SimpleThreadBundle(size_t size, init_fun_t init_fun, Strategy strategy);
SimpleThreadBundle(size_t size, Strategy strategy)
: SimpleThreadBundle(size, Runnable::default_init_function, strategy) {}
explicit SimpleThreadBundle(size_t size)
: SimpleThreadBundle(size, USE_SIGNAL_LIST) {}
~SimpleThreadBundle() override;
size_t size() const override;
using ThreadBundle::run;
void run(Runnable* const* targets, size_t cnt) override;
};
} // namespace vespalib
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