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

Subject: Re: [boost] boost lockfree queue.hpp - alternate implementation w/o compare_exchange
From: Tim Blechmann (tim_at_[hidden])
Date: 2015-10-21 04:15:27

interesting ... it might take me a bit to have a closer look at the
code, though from a quick look, it seems like a variation of the
wait-free ringbuffer, which is available in the wild?

btw, one thing i could spot right away: you are using
std::this_thread::yield() ... which is blocking the caller thread and
not allowed e.g. in real-time applications ...

On 2015-10-21 05:02, boost_at_[hidden] wrote:
> 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
> 
> 
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