RE: More CPUVPs than processors

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 [mailto:owner-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