Re: AFF_SPROC + AFF_NPROCS

From: D.Penfold@Libertel.nl > >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 Sometimes they don't work. :-) >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 Don't start on 0 or 1, as these could be your "initial" CPU, which the OS often wants more of. >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. Well, the affinity doesn't actually bind the CPU VPs to physical CPUs, it says: don't run this CPU VP on any other processor but this one; a subtle but important difference. In other words, this will not (necessarily) cause a CPU VP to tie up a physical CPU, it just won't let the CPU VP move around between physical processors. So I don't think it will cause any particular hassles. On that score. But I believe any number of people of people in tech support don't like affinity. :-) HTH. ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com