The disruptorplus from lewissbaker

Performance defect in disruptorplus::spin_wait ctor

The constructor of class disruptorplus::spin_wait has the call to std::thread::hardware_concurrency(). It affects latency of all
disruptorplus::spin_wait_strategy::wait_until_published() methods:

disruptorplus/include/disruptorplus/spin_wait.hpp

Lines 40 to 50 in 748e354

    
           spin_wait() 
        
           { 
        
               reset(); 
        
           } 
        
           /// \brief 
        
           /// Reset the spin_wait back to its original state. 
        
           void reset() 
        
           { 
        
               m_value = std::thread::hardware_concurrency() > 1 ? 0 : 10; 
        
           }

disruptorplus/include/disruptorplus/spin_wait_strategy.hpp

Lines 51 to 65 in 748e354

    
           sequence_t wait_until_published( 
        
               sequence_t sequence, 
        
               size_t count, 
        
               const std::atomic<sequence_t>* const sequences[]) 
        
           { 
        
               assert(count > 0); 
        
               spin_wait spinner; 
        
               sequence_t result = minimum_sequence_after(sequence, count, sequences); 
        
               while (difference(result, sequence) < 0) 
        
               { 
        
                   spinner.spin_once(); 
        
                   result = minimum_sequence_after(sequence, count, sequences); 
        
               } 
        
               return result; 
        
           }

disruptorplus/include/disruptorplus/spin_wait_strategy.hpp

Lines 142 to 163 in 748e354

    
           template<typename Clock, typename Duration> 
        
           sequence_t wait_until_published( 
        
               sequence_t sequence, 
        
               size_t count, 
        
               const std::atomic<sequence_t>* const sequences[], 
        
               const std::chrono::time_point<Clock, Duration>& timeoutTime) 
        
           { 
        
               assert(count > 0); 
        
               spin_wait spinner; 
        
               sequence_t result = minimum_sequence_after(sequence, count, sequences); 
        
               while (difference(result, sequence) < 0) 
        
               { 
        
                   if (spinner.next_spin_will_yield() && timeoutTime < Clock::now()) 
        
                   { 
        
                       // Out of time. 
        
                       return result; 
        
                   } 
        
                   spinner.spin_once(); 
        
                   result = minimum_sequence_after(sequence, count, sequences); 
        
               } 
        
               return result; 
        
           }

Also, there are some redundant code which trying to hide negative impact of this defect:

disruptorplus/include/disruptorplus/sequence_barrier_group.hpp

Lines 164 to 170 in 748e354

    
           size_t count = m_sequences.size(); 
        
           sequence_t current = minimum_sequence_after(sequence, count, m_sequences.data()); 
        
           if (difference(current, sequence) >= 0) 
        
           { 
        
               return current; 
        
           }

disruptorplus/include/disruptorplus/sequence_barrier_group.hpp

Lines 204 to 210 in 748e354

    
           size_t count = m_sequences.size(); 
        
           sequence_t current = minimum_sequence_after(sequence, count, m_sequences.data()); 
        
           if (difference(current, sequence) >= 0) 
        
           { 
        
               return current; 
        
           }

Possible fix is to save the result of std::thread::hardware_concurrency() in some static variable and reuse it in spin_wait ctor.

Add CMake Support

Nice work! I was able to compile example ¹ with CMake. We can add CMake support for others.

Small typo in README: sequence_t seq = claimStrategy.claim_one(): // <<< Should be ; and missing <iostream> header, see PR. ↩

compile error

disruptorplus/include/disruptorplus/sequence_barrier_group.hpp

Line 202 in e9d7250

    
           sequence_t current = minimum_sequence_after(sequence, count, m_sequences.data());

disruptorplus/sequence_barrier_group.hpp:202:67: error: ‘count’ was not declared in this scope

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Performance defect in disruptorplus::spin_wait ctor

Add CMake Support

compile error

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	spin_wait()
	{
	reset();
	}

	/// \brief
	/// Reset the spin_wait back to its original state.
	void reset()
	{
	m_value = std::thread::hardware_concurrency() > 1 ? 0 : 10;
	}

	sequence_t wait_until_published(
	sequence_t sequence,
	size_t count,
	const std::atomic<sequence_t>* const sequences[])
	{
	assert(count > 0);
	spin_wait spinner;
	sequence_t result = minimum_sequence_after(sequence, count, sequences);
	while (difference(result, sequence) < 0)
	{
	spinner.spin_once();
	result = minimum_sequence_after(sequence, count, sequences);
	}
	return result;
	}

	template<typename Clock, typename Duration>
	sequence_t wait_until_published(
	sequence_t sequence,
	size_t count,
	const std::atomic<sequence_t>* const sequences[],
	const std::chrono::time_point<Clock, Duration>& timeoutTime)
	{
	assert(count > 0);
	spin_wait spinner;
	sequence_t result = minimum_sequence_after(sequence, count, sequences);
	while (difference(result, sequence) < 0)
	{
	if (spinner.next_spin_will_yield() && timeoutTime < Clock::now())
	{
	// Out of time.
	return result;
	}
	spinner.spin_once();
	result = minimum_sequence_after(sequence, count, sequences);
	}
	return result;
	}

	size_t count = m_sequences.size();

	sequence_t current = minimum_sequence_after(sequence, count, m_sequences.data());
	if (difference(current, sequence) >= 0)
	{
	return current;
	}

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