RE: AFF_SPROC + AFF_NPROCS

You did not state your platform. These parameters are not supported on all platforms. Their use should reduce UNIX overhead caused by context switching. They should not cause workload to be spread over different CPU VPs. Spreading NETTYPE connections over all CPUs can help to spread the workload. See Art Kagel's article in Tech Notes 1998, Vol 8, Issue 3 for more helpful information on this subject. http://www.informix.com/informix/services/ilink/pubs/technote/tn98v8i3/chap1 .htm -----Original Message----- From: D.Penfold@Libertel.nl To: informix-list@iiug.org Sent: 2/10/00 7:18 AM Subject: AFF_SPROC + AFF_NPROCS Does anyone out there have any warnings/advice re: setting the above parameters? I'm administering a system at the moment that has 6 cpus, and NUMCPUVPS set to 5, but neither of the AFF parameters are set. onstat -g glo shows very uneven cpu vp activity, and top shows very uneven cpu activity. I immediatley suggested setting: AFF_NPROCS 5 AFF_SPROC 0 or 1 Someone else panicked at the suggestion, saying that it meant that informix would take up too many resources and not leave the in house application with enough, which may need up to 50% of the cpu activity. The only problem I could think of was if some of these individual in house application processes take up a lot of cpu time, and may need to be individually bound to specific cpus. This is apparently not the case, its lots of small processes. Accordingly, I said that the way to deal with this is to allocate a lower NUMCPUVPS, 4, 3 or even 2, and spread these around evenly with the AFF parameters, not to just let them all bunch up together. Someone else has put these changes on hold, saying they want to look into what cpus perform intterupts or any other vital function. Any advice on any of this? e.g. my approach, anything I've missed, and also what means/tools could you use to determine what cpus perform special unique functions and need to be protected. Thanks in Advance Dominic