Re: RE: [COMMITTERS] pgsql/src/backend/access/transam ( xact.c xlog.c)

* Bruce Momjian <pgman@candle.pha.pa.us> [001116 11:59] wrote:
> > At 02:13 PM 11/16/00 -0500, Bruce Momjian wrote:
> > 
> > >> I think the default should probably be no delay, and the documentation
> > >> on enabling this needs to be clear and obvious (i.e. hard to miss).
> > >
> > >I just talked to Tom Lane about this.  I think a sleep(0) just before
> > >the flush would be the best.  It would reliquish the cpu slice if
> > >another process is ready to run.  If no other backend is running, it
> > >probably just returns.  If there is another one, it gives it a chance to
> > >complete.  On return from sleep(0), it can check if it still needs to
> > >flush.  This would tend to bunch up flushers so they flush only once,
> > >while not delaying cases where only one backend is running.
> > 
> > This sounds like an interesting approach, yes.
> 
> In OS kernel design, you try to avoid process herding bottlenecks. 
> Here, we want them herded, and giving up the CPU may be the best way to
> do it.

Yes, but if everyone yeilds you're back where you started, and with
128 or more backends do you really want to cause possibly that many
context switches per fsync?

-- 
-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]
"I have the heart of a child; I keep it in a jar on my desk."