[MUD-Dev] Multi-threaded mud server.

[Jon A. Lambert]

On 28 May 99,, Ross Nicoll wrote:
> On Sun, 16 May 1999, David Bennett wrote:
> 
> > >Semaphores were the original plan, but as I understand it, this would
> > >require a new semaphore for each object. As we're looking at 10,000+
> > >objects, that's a _lot_ of semaphores.
> > Well...  You could do a system that only generated a semphore when it was
> > needed...  As in you have some nice bit you set in the structure for
> > reading/writing and another bit you set for being locked.  Then if it goes
> > to do a normal semphore unlock and it finds that a semaphore is needed it
> > grabs it correctly.  Or just waits on an event or something.
> Good idea, but unfortunately it's still possible two processes to
> simultaneously do the check, find no semaphore, and both to then try
> allocating a semaphore, at the same time. Which would just result in a
> mess, really...
>

I'm not sure what synchronization objects you have available, but...

I use Event objects when waiting for external signals (sockets and disk).
And I use Critical Sections liberally in classes, especially in Factory 
classes to ensure that exclusive access is obtained until object 
constructors complete.  I had all kinds of problems in this area, BTW.  
You might not, but it's something to look closely at. :)   

I also use a variation on Critical sections called Metered Critical 
Sections (there's a document describing them at www.msdn.com).  Anyway 
the variation, I most frequently use allows multiple readers OR one 
exclusive writer.  

Mutexes and Semaphores are the most expensive synchronization objects
on my platform. YMMV

I also make use of InterlockedIncrement, InterlockedDecrement, and 
InterlockedExchange.  What they do is allow you to provide some very 
lightweight non-interruptable function access to shared variables.


--
--*     Jon A. Lambert - TychoMUD Email:jlsysinc at ix.netcom.com             *--
--*     Mud Server Developer's Page <http://pw1.netcom.com/~jlsysinc>      *--
--* To fight the empire is to be infected by its derangement. Whosoever    *--
--* defeats part of the empire becomes the empire; it proliferates like a  *--
--* a virus... thereby it becomes its enemies." -- P.K. Dick               *--


_______________________________________________
MUD-Dev maillist  -  MUD-Dev at kanga.nu
http://www.kanga.nu/lists/listinfo/mud-dev