Asp Forum - About my previous post

Ramine

12/6/2014 11:49:00 PM

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 milliseconds with Seqlock and it takes around 165
milliseonds with the Dmitry Vykov distributed reader-writer mutex using
a rwlock, it takes 165 milliseconds 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
milliseconds compared to the 25 seconds, 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-seque...

Thank you,
Amien Moulay Ramdane.

comp.programming

About my previous post

Ramine

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