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About my previous post

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Hello,


I have wrote in my previous post this:


"I have benchmarked the distribute reader-write lock of Dmitry Vyukov 
and i have found that it is so expensive that it takes over 16 or 32 
cores to make it scale as Seqlock with 4 cores"


You will say that in computer science we need proof of what i am
saying above..

Here is my proof by using the Amdahl's law:


The distributed reader-writer mutex using a rwlock of Dmitry Vyukov 
don't eliminate the full memory barrier in the reader side of the RWLock 
used by the distributed reader-writer mutex of Dmitry Vyukov, this full 
memory barrier does take 350 CPU cycles on my quadcore Q6600 and i think 
it takes around the same cycles on Intel i7, i have just done a parallel 
program benchmark between Seqlock and the distributed reader-writer 
mutex of Dmitry Vyukov using a rwlock on x86 and it gives on read-mostly 
scenario 25 microseconds with Seqlock and it takes around 165 
microseconds  with the Dmitry Vykov distributed reader-writer mutex 
using a rwlock, it takes 165 microseconds because it is using an 
expensive call to GetCurrentProcessorNumber() of Windows and it is using 
full memory fences on the reader side and it is using more code on the 
reader side , but this GetCurrentProcessorNumber() and full memory 
fences on the Dmitry Vyukov algorithm are part of the parallel part of 
the Amdahl's law, so they will scale, but they are so expensive compared 
to Seqlock that it takes  16 to 32 cores on small to medium reader 
section size to make it scale as a Seqlock on 4 cores, cause look at the 
165 microseconds compared to the 25 microseconds, there is a big 
difference, this is my proof , so the distributed reader-writer mutex 
using a rwlock is scalable but it is too much slow than Seqlock or RCU 
on reader-mostly scenarios, this is why i have invented my scalable 
distributed sequential lock that beats Seqlock and that is as fast and 
as scalable as both Seqlock and RCU on read-mostly
scenarios.

You can download my scalable distributed sequential lock version 1.1 from:

https://sites.google.com/site/aminer68/scalable-distributed-sequential-lock


Thank you,
Amien Moulay Ramdane.

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About my previous post Ramine <ramine@1.1> - 2014-12-06 15:51 -0800

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