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Conditional variable instead of sleep_for #23

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46 changes: 46 additions & 0 deletions cond_variable_instead_sleep_for.patch
Original file line number Diff line number Diff line change
@@ -0,0 +1,46 @@
--- worker.hpp Thu Mar 22 23:20:12 2018
+++ worker.hpp Sat Mar 24 22:28:13 2018
@@ -2,6 +2,8 @@

#include <atomic>
#include <thread>
+#include <condition_variable>
+#include <mutex>

namespace tp
{
@@ -78,6 +80,8 @@
Queue<Task> m_queue;
std::atomic<bool> m_running_flag;
std::thread m_thread;
+ std::mutex m_conditional_mutex;
+ std::condition_variable m_conditional_lock;
};


@@ -121,6 +125,7 @@
inline void Worker<Task, Queue>::stop()
{
m_running_flag.store(false, std::memory_order_relaxed);
+ m_conditional_lock.notify_all();
m_thread.join();
}

@@ -140,6 +145,7 @@
template <typename Handler>
inline bool Worker<Task, Queue>::post(Handler&& handler)
{
+ m_conditional_lock.notify_one();
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I think you should do the notification after you have added the job to the queue otherwise the worker might try to pull the job too soon

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Мммммммм, in theory may be. In practice....hardly. Also, how you imagine such implementation? I see only one way - additional local variable requires, so more assembler, slower execution... No, not so good idea.

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@KayEss KayEss Jun 13, 2020

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If you're going to worry about the cost of that it might be more interesting to look at the call to notify_one you have for every posted job. Compared to that cost saving the bool result is essentially free.

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If you're going to worry about the cost of that it might be more interesting to look at the call to notify_one you have for every posted job. Compared to that cost saving the bool result is essentially free.

Take a look on my own fork of this library. Done long time ago. :) This PR is years old :)

Anyway, you can make you own fork, perform benchmark and compare. :)

return m_queue.push(std::forward<Handler>(handler));
}

@@ -171,7 +177,8 @@
}
else
{
- std::this_thread::sleep_for(std::chrono::milliseconds(1));
+ std::unique_lock<std::mutex> lock(m_conditional_mutex);
+ m_conditional_lock.wait(lock);
}
}
}