Re: 10046, Unaccounted for Time, Aix 5.3 -- How to Determine Process Pre-Emption

I'm not too familiar with aix but Solaris has several scheduling algorithms (Real Time, Fair Share, Time Share, etc...) These have different ranges of priorities. Do a man on ps. It probably has options to show priority and scheduling class (i.e. the algorithm). Mixing different algorithms in a single VM can cause problems. 

Here's the command in solaris that shows that info:

ps -ef -o user,pid,project,class,zone,pset,pri,nlwp,psr,time,args
As already mentioned, vmstats/sar should also give you a good clue as to whether processes are struggling to get on the CPU.
There is a great Solris Internals book that describes all the scheduling algorithms among other things. I presume there is a similar reference for AIX. Also, I'd recommend Millsap's book for a better understanding of how/why unaccounted for time occurs. 

Kerry Osborne
Enkitec
blog: kerryosborne.oracle-guy.com






On Dec 2, 2009, at 2:13 PM, Larry G. Elkins wrote:


Listers,
SA's asking for assistance on how to tell if a process is being impacted and to what degree by processor pre-emption. AIX 5.3. Asked in the context of trouble-shooting some significant unaccounted for time issues in 10046 trace files (e.g. 14 of 16 seconds unaccounted for vendor process, 300 of 700 
seconds unaccounted for vendor batch job, etc). SA's have "ruled out"
overhead of writing the trace file so now looking at the pre-emption aspect. A bit out of my league, and I find plenty of approaches in IBM docs, and from people on this list (but geared more towards Solaris and other flavors, not Aix). 9.2.0.8 EE and 10.2.0.4 EE, "static" and dynamic LPAR's, seen on 
various boxes and databases.

Larry G. Elkins


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