> > > > * Order duplicate index entries by tid
> > >
> > > In other words - add tid to index key: very old idea.
> >
> > I was thinking during index creation, it would be nice to
> > order them by tid, but not do lots of work to keep it that way.
>
> I hear this "not do lots of work" so often from you -:)
> Days of simplicity are gone, Bruce. To continue, this project
> requires more and more complex solutions.
Yep. I can dream. :-)
> > > > * Add queue of backends waiting for spinlock
> > >
> > > We shouldn't mix two different approaches for different
> > > kinds of short-time internal locks - in one cases we need in
> > > light lmgr (when we're going to keep lock long enough, eg for IO)
> > > and in another cases we'd better to proceed with POSIX' mutex-es
> > > or semaphores instead of spinlocks. Queueing backends waiting
> > > for spinlock sounds like nonsense - how are you going to protect
> > > such queue? With spinlocks? -:)
> >
> > Yes, I guess so but hopefully we can spin waiting for the queue lock
> > rather than sleep. We could use POSIX spinlocks/semaphores now but we
> > don't because of performance, right?
>
> No. As long as no one proved with test that mutexes are bad for
> performance...
> Funny, such test would require ~ 1 day of work.
Good question. I know the number of function calls to spinlock stuff is
huge. Seems real semaphores may be a big win on multi-cpu boxes.
> > Should we be spinning waiting for spinlock on multi-cpu machines? Is
> > that the answer?
>
> What do you mean?
On a single-cpu machine, if you can't get the spinlock, you should just
sleep and let the process who had it continue. On a multi-cpu machine,
you perhaps should just keep trying, hoping that the process who holds
it finishes soon. I wonder is we should find some kind of test on
postmaster startup that would test to see if we have multiple cpu's and
change from spinlock sleeping to spinlock spin-waiting.
Add to this that fact we can't sleep for less than on clock tick on most
machines, 10ms, and the spinlock stuff needs work.
TODO updated:
* Improve spinlock code, perhaps with OS semaphores, sleeper queue, or
spining to obtain lock on multi-cpu systems
--
Bruce Momjian | http://candle.pha.pa.us
[EMAIL PROTECTED] | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
---------------------------(end of broadcast)---------------------------
TIP 6: Have you searched our list archives?
http://www.postgresql.org/search.mpl
