Re: Single cpu vp woe

Andrew Hamm wrote: > Neil Truby wrote: > >>9.20 UC3 on Red Hat 7. >> >>This site is running the time series datablade in production on a 2- >>cpu box. It's all working fine. >> >>For reasons we needn't go into they want to move to a single cpu box. >>[ETC] Andrew, I disagree. NOAGE has nothing to do with allowing IDS to take over the "complete allocation of the cpu cycles" of one or more processors. The reason for NOAGE is that some OSes (most aggressively HPUX and less so Solaris) progressively reduce the OS timeslice priority of any process which runs a long time ('long' defined by a kernel parameter but typically about an hour IB). For a server like IDS which can literally run forever (in hardware speak that means until the machine crashes), it means that unless the machine is a dedicated server with no other processes running on it, IDS will progressively become more and more starved for CPU cycles until its oninit processes are rarely in a 'run' state. Setting NOAGE to 1 notifies the OS that this process is SUPPOSED to run for a long time and is not just a runaway or resource hog. With NOAGE set to 1 the OS will not reduce the initial priority of the oninit processes that make up the server and performance will be consistently good over time. Meanwhile, to the original question, I'd say give 2 CPU VPs with MULTIPROCESSOR set to 1 a try. In my own tests and those of others, reported here over the years, with todays fast processors (tests showed about 550MHZ or 750 for x86 CPUs is the slowest CPUs that this works for), running 2 (or more for multi-GHZ or multi-core CPUs) CPU VPs per physical CPU can indeed increase throughput by measurable amounts on dedicated servers without impacting system functions. Art S. Kagel > Neil, you haven't mentioned the settings for NOAGE. I'm assuming you have > NOAGE=0 on both systems, or have at least switched it off on the single > CPU box? Notwithstanding Richards important points about hyperthreading > Intels, following are my expectations. > > On the 2 CPU box: > > - if you set single cpuvp and NOAGE=1, you'll basically guarantee upto > complete allocation of the cpu cycles of one processor. Since you only > have single cpuvp, you will not get any cpuvp type activity on the other > CPU. Processes like 4GL, Java, Apache, etc and also the sundry engine > processes will probably drift to the free CPU if the database keeps one > processor boiling. > > - if you set dual cpu vp and NOAGE=1, you'll basically guarantee upto > complete allocation of the cpu cycles of the two processors. You'd better > hope that nothing else is being attempted on this machine apart from > database activity, because if the database gets really busy, this > configuration will choke out just about every other task. I have seen HP's > and Intel crippled by this kind of mistake, however DSS is a prime example > of a system where total cpu hogging can be appropriate because there are > no 4GL or other processes competing for cpu cycles. > <SNIPPED as more of the same> Art S. Kagel

----- Original Message ----- From: "Art S. Kagel" <kagel@bloomberg.net> Newsgroups: comp.databases.informix To: "Andrew Hamm" <ahamm@mail.com> Sent: Wednesday, February 23, 2005 7:42 PM Subject: Re: Single cpu vp woe > Meanwhile, to the original question, I'd say give 2 CPU VPs with > MULTIPROCESSOR set to 1 a try. In my own tests and those of others, > reported here over the years, with todays fast processors (tests showed > about 550MHZ or 750 for x86 CPUs is the slowest CPUs that this works for), > running 2 (or more for multi-GHZ or multi-core CPUs) CPU VPs per physical > CPU can indeed increase throughput by measurable amounts on dedicated > servers without impacting system functions. However, the user wants to run on ONE physical cpu and has deliberately taken one out of his 2-way box. The reason is that he wishes to minimise his IBM Informix licence cost. It isn't delivering the performance he wants, but he wants to know if there's an inherent reason why.