[boost] boost lockfree queue.hpp - alternate implementation w/o compare_exchange

Subject: [boost] boost lockfree queue.hpp - alternate implementation w/o compare_exchange
From: boost_at_[hidden]
Date: 2015-10-20 23:02:34

Is there any interest in an alternate implementation of a lockfree queue 
that doesn't use compare_exchange (assuming it is correct, or can be 
made to be correct)?

I have a multi-producer / multi-consumer implementation that generally 
doesn't suffer nearly as much from contention.  On my hardware (an older 
high-end 64 bit x86 workstation) I get roughly comparable throughput 
with existing boost lockfree queue with 1 producer and 1 consumer.  With 
4 producers and 4 consumers I get about 3x throughput gain on existing 
boost lockfree queue.  However, this implementation has a weakness, it 
suffers in over subscription scenarios (threads in middle of push/pop 
that lose their time-slice); with twice as many threads as cores its 
performances is comparable to boost lockfree queue (using 
try_push/try_pop, otherwise throughput is down the toilet), and with 4x 
thread/core ratio the throughput is somewhat less than boost lockfree 
queue.

This was tested on Windows 7 x64 with Inel Xeon X5355 x 2 (2 sockets w/ 
4 cores a piece) @ 2.66 Ghz and 32 GB RAM @ 667 MHz.

The implementation can be found here:
https://github.com/benmccart/GuarunteedMpmcQueue/blob/master/queue/queue.hpp

Is the implementation correct?  Can anyone spot any race conditions, or 
conditions under which the implementation would fail to work as expected 
(other than queue is full/empty or over-subscription)?

~Ben