HP/Informix performance

I've noticed this on several HP systems. They seem to hit a "wall" at a certain load average. On a very heavily-loaded system, they will perform well up to say, a 10.0 load average. When it gets to about 10.3 to 10.5, performance gets shot to hell, decreasing by a factor of 10x or so. We've checked all the obvious OS and Informix suspects, the main one being swapping (none), and nothing seems to work except reducing the load or adding cpus. Obviously, all systems have limits, but I've noticed that the HPs seem to have a very narrow range between acceptable loads and killer loads. We're using kaio. I've seen some other posts about kaio degrading at a high load. Since kaio is a UNIX system function, I wonder if the kaio problem and my "wall" may be part and parcel of the same problem. Has anybody else run into these limits, and more importantly, does anybody have an explanation for exactly what's happening here? Is this simply a case of system thrashing at high cpu loads? Joe -- --------------------------------------------------------------------------- Joe Lumbley(jlumbley@netcom.com) ---------------------------------------------------------------------------