Hello,
So in this post i will explain to you what is exactly my invention that is my scalable MLock algorithm.. If you look the Enter() method of my scalable MLock algorithm you will read this(that's easy to undertand the code in Object Pascal) , and read my explanation after: You can download the source code here: https://sites.google.com/site/aminer68/scalable-mlock == procedure TMLock.Enter; var prev,fcount1:PListEntry; k:integer; Buffer1:pointer; begin Buffer1 := AllocMem(SizeOf(TListEntry) + Alignment); FCount1 := PListEntry((int(Buffer1) + Alignment - 1) and not (Alignment - 1)); fcount1^.Data:=0; fcount1^.Next:=nil; fcount1^.mem:=buffer1; long(prev) := LockedExchange(long(m_head), long(fcount1)); prev.next := fcount1; if (flag=1) then begin if (m_tail=prev) then if CAS(flag,1,0) then begin fcount1^.Data:=-1; exit; end; end; k:=1; repeat if fcount1^.data=1 then begin freemem(fcount1^.mem); break; end else if fcount1^.data=2 then begin fcount1^.Data:=-1; break end; if (flag=1) then begin if (m_tail.next.next=fcount1) then if CAS(flag,1,0) then begin fcount1^.Data:=-1; break; end; end; inc(k); if (k mod 140)=0 then {$IFDEF FPC} ThreadSwitch; {$ENDIF} {$IFDEF Delphi} sleep(0); {$ENDIF} asm pause end; until false; end; === First i am allocating a Buffer1 struct and using fcount1 that is a pointer to a 64 bytes aligned record and i am assigning zero to fcount1^.Data cause the threads that enter will have to wait for there turn and for fcount1^.Data to become 1 to enter the scalable Lock except for the first thread that enters the lock, the first thread that enter the lock will find the "flag" variable equal to 1 and notice with me that the CAS(flag,1,0) will succeed for the first thread that enters the Enter() method... Look that i am using this inside the source code: long(prev) := LockedExchange(long(m_head), long(fcount1)); prev.next := fcount1; this is a waitfree queue and the push() and the pop() inside my scalable MLock algorithm are waitfree... So notice with me that the threads on the Enter() method will enter a repeat-until loop waiting for there turn to enter, and notice that the CAS will be touched rarely , i have benchmarked and collected some empiric statistics and i have noticed that the CAS inside the repeat-unil loop inside the Enter() method will be touched only 1% of the time, so the threads will wait 99% of the time for fcount1^.data to become 1 or fcount1^.data to become 2 , and notice that fcount1^.data inside the Enter() method is not generating cache-lines transfers for each thread waiting in the Enter() method, cause fcount1^.data is only touched by its correponding threads on its local cache, this is why my MLock algorithm is scalable, cause it minimizes efficiently the cache-coherence traffic. For the Leave() method it is waitfree and it is easy to prove that, just look at the source code and you will notice that even though there is a repeat-until loop inside the Leave() method , my algorithm will not loop more than 2 times inside the Leave() method, so it makes my algorithm waitfree and my algorithm can be used on parallel and realtime safety critical systems. And also you will notice easily that my scalable MLock is FIFO fair , so it's starvation-free. This is a node based Lock that is scalable, FIFO fair and starvation-free. - Discovered by Amine Moulay Ramdane - This lock is scalable - It has the same space requirement as the scalable MCS lock - Doesn't require a local "queue node" to be passed in as a parameter as is doing the MCS and CLH locks. - Spins only on local locations on a cache-coherent machine - And it's fast. Please read also this: A bigger problem with the MCS lock is its API. It requires a second structure to be passed in addition to the address of the lock. The algorithm uses this second structure to store the information which describes the queue of threads waiting for the lock. Unfortunately, most code written using spinlocks doesn't have this extra information, so the fact that the MCS algorithm isn't a drop-in replacement to a standard spin lock is a problem. An IBM working group found a way to improve the MCS algorithm to remove the need to pass the extra structure as a parameter. Instead, on-stack information was used instead. The result is the K42 lock algorithm: Unfortunately, the K42 algorithm has another problem. It appears that it may be patented by IBM. Thus it cannot be used either. (Without perhaps paying royalties to IBM.) So you have to know that my scalable MLock doesn't require a local "queue node" to be passed in as a parameter as is doing the MCS and CLH locks, my scalable MLock doesn't require any parameter to be passed, just call the Enter() and Leave() method and that's all. You can download my scalable node based Lock that is FIFO fair and waitfree from: https://sites.google.com/site/aminer68/scalable-mlock Thank you, Amine Moulay Ramdane. -- --- You received this message because you are subscribed to the Google Groups "Scalable Synchronization Algorithms" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/lock-free/0fe20a06-baf4-46a7-8c21-edbd80d142d8%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
