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I have thought more about lockfree algorithms..

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From	aminer <aminer@toto.net>
Newsgroups	comp.programming.threads, comp.programming
Subject	I have thought more about lockfree algorithms..
Date	Sun, 18 May 2014 19:07:06 -0700
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Hello,


I have thought more about lockfree algorithms..

I think that lockfree algorithm are very very bad , sooooo bad !

I have told you before that i have benchmarked the following
concurrent FIFO queues that uses lockfree machenism..

This one:

http://code.google.com/p/omnithreadlibrary/downloads/detail?name=OmniThreadLibrary-3.03b.zip&can=2&q=

This one:

http://www.odsrv.com/RingBuffer/RingBuffer.htm


And what i have told you is that they are 2x times slower than
my new algorithm that is not lockfree, here is my new algorithm:

https://sites.google.com/site/aminer68/concurrent-fifo-queue-1


But that`s not the complete picture, cause what i have done is
testing those lockfree algorithmz under contention with only 4 cores,
but as soon as you will use more and more cores the throughput of those
lockfree algorithms will drop more and more and this is not
acceptable.. but why the throughtput of lockfree algorithms will drop 
more and more with more and more cores ? cause lockfree algorithms don't 
minimize efficiently the cache-coherence traffic as is doing my new 
algorithm above, so under contention and with more and more cores the 
lockfree mechanism of those lockfree algorithms causes more and more 
contention because the threads that fail will slow more and more the 
next thread that will succeed because of high cache-coherence traffic 
and  high contention on the bus ... and this is not acceptable !, so i 
think that lockfree algorithms are complete crap
that must be avoided ! other than that lockfree algorithms are not 
starvation-free.



Thank you,
Amine Moulay Ramdane.

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I have thought more about lockfree algorithms.. aminer <aminer@toto.net> - 2014-05-18 19:07 -0700

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