Re: PostgreSQL

Johnny Billquist a écrit :
> Yes, I took a rather restricted view.
> I was talking (and thinking) about the bus transactions, not machine 
> language (or some even higher language constructs).

There are been some good answers over "what is" a write. Just to add one 
thing that have been overlooked: cache. Normal writes goes on the cache, 
nowdays. 68020/68030 had a write-through cache, but most of the modern 
processors operate in write-back mode. That means that a write can be 
much of complex thing, invalidating lines in many other peers (snoop 
operation).
However, a r/m/w locked instruction should always be performed in 
write-through mode, in order to avoid the overhead of changing other's 
cache status. Semaphores should not be cached.

Vincent