Re: Informix and NOAGE

Jim Jordan wrote: > > In article <33CC2D68.307@bellsouth.net>, > MIS Dept <whsmis1@bellsouth.net> wrote: > >Saeed Talebbeik wrote: > > >> Both NOAGE and processor affinity can boost the performance. > >> However look into the machine notes of your platform to see if > these two > >> features are really supported. Apparently on HPUX NOAGE is > supported. > > >> I suggest to experiment with NOAGE and see what happens. I have > heard of > >> lockup problems such as this but I have not seen it myself. > > >>NOAGE is officially supported, but we've been bitten by that nasty > bug. > >Informix literally took over the system; the oninit processes were > >running with a priority of -16. > > That's because in 7.1x on HP-UX NOAGE is implemented using the POSIX > scheduler class (man rtsched for details; POSIX is the only way to get > negative priorities). Anything ready to run in this class gets > priority > over everything else. Informix, being a good database server trying > to > minimise context switching, tries to do as much as it can when it gets > the CPU, preferring to busy-wait for a while rather than relinquish > the > processor. > > 7.22 uses HP's real-time-priority class (prios between 1 and 127; the > smaller the number, the higher the priority) for NOAGE, though I don't > know what priorities it assigns to the various classes of VPs. This > is > much more sensible. > > We've written a startup script for 7.14 that does much the same as > what > we've been told 7.22 does with NOAGE set. This script starts the > server, waits for recovery to complete, sees if additional lio and pio > VPs are needed to handle mirroring and kicks those off before the > real-time server process does, does onstat -g glo, figures out what > pid > corresponds to what VP (awk is wonderful), moves some up into > real-time > priority, and bounces others back into time-share class. It's easy > once > you understand what you have to do. > > Be aware that any additional VPs that Informix creates on its own will > inherit the priority of the parent VP--a CPU vp. It's better to > create > all the VPs you need when you start the server, then move them around > to > where you want them to be (do you really need a high-priority lio > VP?). > > However, this brings its own set of gotchas, particularly when running > on a uniprocessor box. Whenever a high-priority VP is waiting for a > lower-priority VP to clean something up, it will run away in a > busy-wait > loop. If you run Informix at higher-than-normal priorities, keep a > still-higher-priority terminal window handy, and unset autologout so > it > doesn't disappear of its own accord. > > Setting your own real-time priorities is not exactly unsupported; > Informix would prefer that you use NOAGE, but they understand that > it's > badly broken in 7.1x and deemed to be fixed in 7.22. Informix tech > support apparently considers priority tuning apart from NOAGE to be > similar to kernel tuning. If it works, life is good. If it doesn't, > you have more work to do. But if it turns up a real bug, they'll take > the report. > > Useful tools for diagnosis: one or two high-priority windows, onstat > -g > ath, onstat -g tpf <thread_id>, onstat -g wai, access to either the > console or power switch for stuff that locks out the high-priority > windows. If Informix runs away, write a script to bring it back to > its > senses, (i.e., time-share priority), then restore the real-time stuff. > Of course, any manipulation of process priority requires you to be > root, > and all caveats such as YMMV apply. > > Have fun. This all sounds great, and a lot of fun, but wouldn't it be easier to just upgrade to version 7.22? ;-) Or even version 7.23. Cheers, -- Mark. +----------------------------------------------------------+-----------+ |Mark D. Stock - Informix SA http://www.informix.com |//////// /| |mailto:mdstock@informix.com FAQ http://www.iiug.org |///// / //| | +-----------------------------------+//// / ///| | Tel: +27 11 807 0313 |If it's slow, the users complain. |/// / ////| | Fax: +27 11 807 2594 |If it's fast, the users keep quiet.|// / /////| |Cell: +27 83 250 2325 |Therefore, "No news: travels fast"!|/ ////////| +----------------------+-----------------------------------+-----------+