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About my RWLockX 2.11 algorithm

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Hello,

I will explain my new RWLockX algorithm (a scalable RWLock)...

My previous algorithms were not starvation-free, so if you have
frequent writes the reader threads may starve for long time or starve
completly.


So i had to be smarter than that , so if you look at my
previous algorithm, read this:

http://pages.videotron.com/aminer/rwlock1.html


Inside the  TRWLOCK.RLock() method i had done this:


if (FCount3^.fcount3 = 0)
then break
else
  begin
    LockedExchangeAdd(FCount1^[myid].fcount1,-1);
  end;


So if the readers loop back so the algorithm will not
be starvation-free and if there is more writes the  reader
threads may starve for a long time or starve completly.

So i had to change my previous algorithms and avoid completly the 
looping back so that to avoid starvation.

And here is what i have done in my new RWLockX algorithm that
is starvation-free:

i have changed this part inside the TRWLOCK.RLock() method with this:


if (FCount3^.fcount3 = 0)
then break
else
  begin
   LockedExchangeAdd(nbr,1);
   LockedExchangeAdd(FCount1^[myid].fcount1,-1);
   event1.waitfor(INFINITE);
   LockedExchangeAdd(FCount1^[myid].fcount1,1);;
   LockedExchangeAdd(nbr,-1);
   break;
  end;


and in the write side inside the TRWLOCK.WLock() method
i have added this:

repeat;
  event1.setevent;
  event1.resetevent;
until nbr=0;

So that to avoid completly starvation and so that to avoid
a deadlock.

So my new scalable RWLockX algorithm supports now all the following
requirements:


1- It uses my SemaMonitor , hence it uses less CPU ressources.

2- It scales on multicores

3- It is  starvation-free

4- it is portable.


You can download all the variants of my scalable RWLock 2.11 from:

http://pages.videotron.com/aminer/


Thank you,
Amine Moulay Ramdane.

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About my RWLockX 2.11 algorithm aminer <aminer@toto.net> - 2014-01-28 15:40 -0800

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