NOAGE is set and the priority of the process does not change over time.
I will get and post an onstat -g spi. I have them stashed away. There
were a couple of long spins out there [usually about 6]. Your KIO theory
might hold some merit since io rates definitely improve with the extra
CPUs and the additional kio threads do get used. Not excessively but it
every indication is that it makes a difference.

-----Original Message-----
From: owner-informix-list@iiug.org [mailtowner-informix-list@iiug.org]
On Behalf Of David Williams
Sent: Wednesday, February 09, 2005 6:44 PM
To: informix-list@iiug.org
Subject: Re: More CPUVPs than processors

"Mark" <mark@vuntec.com> wrote in message
news:<1107909506.05b010d31b61d05ef5b592c7476757b2@ teranews>...
> Thanks all for your responses. I might see what happens if I renice
the
> oninit processes to make them run more often/longer. I can't help but
> think that one of the reasons that performance is better is that
adding
> more CPUVPs effectively doubles the amount of CPU time IDS is getting.
>

I assume you have NOAGE set to 1 and it works on your platform?

This keeps bugging me...with more CPUVPS than physical CPUS we should
just be spending more time context switching between VPS. Threads can
migrate from one VP to another so e.g. 6 Physical CPUS = 6 active
CPU VPs..where do the other ones run? Surely all we are getting is
more context switching, more CPU cache flushing, more CPU time spent
in the OS scheduler code so where is the benefit? All I can think of
is a) Informix latch issue which scales with more CPUS(More latches =
more concurrency) b) OS is crap? c) more CPU VPS = more KAIO requests
which can be outstanding at one time so we can keeping the queue of
requests per controller deeper and so elevator sorting is more
effective..do the KAIO queues have a fixed max depth? Informix need to
investigate..

Can someone check onstat -g spi sorted bu num waits and see if it is
different?
Otherwise Informix (IBM) need to do some serious investigation why
this is happening!!

sending to informix-list