Subject: Re: PostgreSQL
To: Johnny Billquist <email@example.com>
From: Vincent <firstname.lastname@example.org>
Date: 02/02/2006 21:56:29
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
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.