RE: AFF_SPROC + AFF_NPROCS

Dominic, My particular experiences has seen a significant performance improvement at all the sites I've set the AFF's parameters. I set AFF_SPROC to 1 rather than 0 - just in case there are special requirements for the first CPU and AFF_NPROCS to one less than the total number. I recommend this as a starting point and then run heavy monitoring for a week or two (appl_jobs and oninit Unix system secs vs Informix vp secs)- i.e. lots of ps -ef's and onstat's and even more awk's to join everything together into readable N min buckets. Geoff Poole > -----Original Message----- > From: D.Penfold@Libertel.nl [SMTP:D.Penfold@Libertel.nl] > Sent: 10 February 2000 15:18 > To: informix-list@iiug.org > 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