POS

[BRIAN SPILSBURY]

MD> I mean, in the extreme case, before pushSTACK(obj) actually pushes `obj', it
MD> calls a startTransaction.  The push occurs, and then a 
MD> endTransaction occurs.   Clearly the cost of actually performing
MD> these transactions all the time is very high.
MD> 
MD> But why can't `startTransaction' be defined like:
MD> 
MD> startTransaction ()
MD> {
MD>   markPageAsDirty(StackPointer,PageVector);
MD>   transactionCount++;
MD> }
MD> 
MD> and `endTransaction' by:
MD> 
MD> endTransaction()
MD> {
MD>   if (transactionCount > transactionThreshold)
MD>     {
MD>       commmitDirtyPages(PageVector);
MD>       transactionCount = 0;
MD>     }
MD> }
MD> 
MD> 

Sure you can do that, but then what's the point? A transaction becomes
kinda meaningless as we can't assume that any given action has transacted.
We lose our measure of atomicity and imho that's the point of a
transactional bd. If you look at the solution I'm proposing its not
hugely different from your example up there, except that its a more genearl
case, and doesn't try to call page flushes transactions, it reserves that
for world-global synhronization.

Brian