Re: 2 or 4 cpu's running Informix OnLine 7.xx

This is a multi-part message in MIME format. --------------678C5BE3E01 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Mike Segel wrote: > With SMP, neither cpu is *idle*. They both or all, pull procs from the > same > stack. Yes, but if you only have one CPU VP and nothing else really running on the machine, the second cpu will be idle a lot of the time. Two cpus cannot run the same process simultaneously. > The only thing is that some of the vendors allow for procs to be > dedicated to a > single CPU. (Why? Cause its a marketing feature. Kinda like the memory > resident > flag in informix. ;-) Much more than a marketing feature. Many SMPs incur a larger overhead to move a process context from one processor to another. In those cases, it makes sense to affinity a process to a processor, such that that process will run on that processor all the time. There are also situations where LRU schemes for keeping stuff in memory isn't the best method (e.g. when access is no constant, but when you need it, you need it asap); in these cases, forced residency is an excellent solution. Other's have pointed out situations where a 2-proc is best tuned as a uni, such as when your applications run on the same machine as the server. Also consider those platforms where kernel async i/o is not supported. If you are doing a lot of i/o in your app, the aio vps are going to be very active, and could force the cpu vps to get context switched more than is ideal. In those situations, it may be worthwhile to tune with the single cpu vp and leave the other physical processor for this other server work. Note that this "tune a 2 proc as a uni" advice is memerly something to consider. If you find your performance to be acceptable tuning a 2 proc with 2 CPUVPS, then terrific - no need to change. If, however, you are finding the performance lacking in such a config, it is worth trying tuning as a uni and see if you performance is better. Use what works for you, not necessarily what the manual says. -- Dave Kosenko, Informix Professional Services **************************************************************************** While it is true that there is more than one way to skin a cat, the cat himself generally fails to appreciate the differences. --------------678C5BE3E01 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="Ifxdiscl.txt" ************************************************************************* Note: please do not send me email asking about features, or asking about Informix problems and how to solve them. I answer what questions I can in this forum (comp.databases.informix) when I have the time to spare. For questions on features, call your local sales rep or check out the Informix web site (http://www.informix.com). For technical problems, call Informix tech support. ************************************************************************* Disclaimer: All opinions expressed in this message are well-reasoned and insightful; needless to say, they are not those of Informix Software, its partners or lackeys. Anyone who says otherwise is itching for a fight. --------------678C5BE3E01--