More CPUVPs than processors

Has anyone found a benefit to running more CPUVPs than processors with 9.4? I have been running some load tests on a dual CPU Itanium/HPUX machine with 8gb ram connected to an EMC disk array. The instance is configured with 2 million buffers, 127 cleaners and LRUs. Rather than configure the instance specifically for bulk loading I have left the instance configured for OLTP activity - in real life many of the jobs that run during normal hours are similar in nature. Instance has 4 dbspaces, 4 spaces used for indexes, 3 temp spaces and a rootdbs. KIO is enabled. All spaces are on the same set of disks [no control over that]. Indexes are created after the data has been loaded. During the load I am finding that the cleaners do not manage to keep up. The LRU min/max are 0.5 and 0.7 respectively. The modified queues will reach as high as 15% dirty. If I have the system configured with 2 CPUVPS there will be idle cleaners. CPU usage rarely exceeds 25-30%. Checkpoints will take many 100s of seconds. I have found that adding CPUVPS results in all the cleaners being active all the time. The queues are much shorter, rarely exceeding 4% and checkpoints generally last no more than a minute. The extra kio threads use about 20-30% of the total CPU time used by all the KIO threads. The results are very repeatable. I have dynamically added/removed CPU VPS during large table loads and seen the effect on the queues and checkpoints. Mark sending to informix-list

Mark wrote: I've always found that for any CPU faster than about 400MHZ (~600 for x86 CPUS) you can run at least 2 CPU VPs per CPU. Now that CPUS are MUCH faster and multi-pipelined and multi-virtual CPU's, you can likely make that 3 or 4 or 5 times # physical CPUs. I think that this is independent of IDS version. Art S. Kagel > Has anyone found a benefit to running more CPUVPs than processors with > 9.4? <SNIP> > > Mark > > sending to informix-list