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    <p>I want to conclude the answer given by <strong>greyfade</strong>, which is based on <a href="http://www.drdobbs.com/high-performance-computing/212201163" rel="nofollow noreferrer">http://www.drdobbs.com/high-performance-computing/212201163</a> (the last part of the article), the optimized code would be <em>(with some modification to suit my naming and coding convention)</em> : ` </p> <pre><code>template &lt;typename T&gt; class LFQueue { private: struct LFQNode { LFQNode( T* val ) : value(val), next(nullptr) { } T* value; AtomicPtr&lt;LFQNode&gt; next; char pad[CACHE_LINE_SIZE - sizeof(T*) - sizeof(AtomicPtr&lt;LFQNode&gt;)]; }; char pad0[CACHE_LINE_SIZE]; LFQNode* first; // for one consumer at a time char pad1[CACHE_LINE_SIZE - sizeof(LFQNode*)]; InterlockedFlag consumerLock; // shared among consumers char pad2[CACHE_LINE_SIZE - sizeof(InterlockedFlag)]; LFQNode* last; // for one producer at a time char pad3[CACHE_LINE_SIZE - sizeof(LFQNode*)]; InterlockedFlag producerLock; // shared among producers char pad4[CACHE_LINE_SIZE - sizeof(InterlockedFlag)]; public: LFQueue() { first = last = new LFQNode( nullptr ); // no more divider producerLock = consumerLock = false; } ~LFQueue() { while( first != nullptr ) { LFQNode* tmp = first; first = tmp-&gt;next; delete tmp; } } bool pop( T&amp; result ) { while( consumerLock.set(true) ) { } // acquire exclusivity if( first-&gt;next != nullptr ) { // if queue is nonempty LFQNode* oldFirst = first; first = first-&gt;next; T* value = first-&gt;value; // take it out first-&gt;value = nullptr; // of the Node consumerLock = false; // release exclusivity result = *value; // now copy it back delete value; // and clean up delete oldFirst; // both allocations return true; // and report success } consumerLock = false; // release exclusivity return false; // queue was empty } bool push( const T&amp; t ) { LFQNode* tmp = new LFQNode( t ); // do work off to the side while( producerLock.set(true) ) { } // acquire exclusivity last-&gt;next = tmp; // A: publish the new item last = tmp; // B: not "last-&gt;next" producerLock = false; // release exclusivity return true; } }; </code></pre> <p>`</p> <p>another question is how do you define CACHE_LINE_SIZE? its vary on ever CPUs right?</p>
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    1. PODoes an optimistic lock-free FIFO queue implementation exist?
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    1. COA good number to choose would be `64` bytes, I think. But you'll probably want to balance it with size, so I'd suggest looking at your target CPUs and choose a size that fits the most common ones you expect to target.
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      1. USgreyfade
    2. COJust a quick note: this is not a forum, so people can't be assume to "browse the thread". If you wish to ask another question, you should better use the "Ask Question" field rather than the "Your Answer" one.
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      1. USMatthieu M.
    3. COI'am indeed re-answering the question, but i was wrong asking in the answer field, I should add new comment under my own new answer. sorry about that.
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