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// Copyright Yahoo. 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 {
const std::vector<Runnable *> *targets;
CountDownLatch *latch;
Work() : targets(0), latch(0) {}
};
/**
* 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() { return (offset < work.targets->size()); }
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) {
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;
typedef std::unique_ptr<SimpleThreadBundle> UP;
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:
Pool(size_t bundleSize, init_fun_t init_fun);
Pool(size_t bundleSize) : Pool(bundleSize, Runnable::default_init_function) {}
~Pool();
SimpleThreadBundle::UP obtain();
void release(SimpleThreadBundle::UP bundle);
};
private:
struct Worker : Runnable {
using UP = std::unique_ptr<Worker>;
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 = USE_SIGNAL_LIST);
SimpleThreadBundle(size_t size, Strategy strategy = USE_SIGNAL_LIST)
: SimpleThreadBundle(size, Runnable::default_init_function, strategy) {}
~SimpleThreadBundle();
size_t size() const override;
void run(const std::vector<Runnable*> &targets) override;
};
} // namespace vespalib
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