Performance Tuning WebWizard

Expanation of Processes

The processes of your system are the running programs. Some are Operating System processes that are vital of the system but most should be user programs and applications.

Processes need CPU time when they need it. AIX/UNIX schedules processes on demand and via a priority queue of runnable processes. Processes also need to have memory. Note that AIX cuts your process up into pages and only the pages currently in use need memory, provided AIX can bring in any missing pages when the program need them - very quickly. This is the difference between the size of the program and its resident set.

One bad process can hurt all the others - so check for any programs that have seemed to get stuck in a loop or should not still be running.

Processes Bottleneck ???

Criteria: one process getting more CPU than necessary

This means you have to know what you expect on your system.

While monitoring processes do not worry about small 1 to 3 seconds of 100% CPU busy but take a longer term view.

Processes monitor Statistics

The processes usage is on the Top Processes Screen of nmon.
The statisics break what the processes is doing into types

CPU% Percentage of the last second running on the CPU You should quickly see which processes are regularly hogging the CPU and if they are sustained or if its small peaks in work.
TIME Total Time on the CPU This is tells you if the process is CPU hungry in the longer term.
Difference between SIZE and RES How much of the program is used regularly This tells you the size of the code and data actually required to run the currently active services.

Notes:

There is no hard and fast rules in processes.
Some systems like a RDBMS in server only mode will have just a handfully of RDBMS processes doing all the work.
Some systems with 100's of processes all taking 2% of the CPU.

What can you do to tune Processes?

Many databases have options to reduce the number of processes for remote user access. This saves CPU cycles scheduling lots of processes.
For SMP and low numbers of processes - Check you are using all CPU's - see SMP tuning.
Check there are no "run-away" processes - i.e. unneeded or looping processes that should have been stopped.
Limit the number of processes each user can run - usefull to stop rogue developers!
Reduce the priority of long running background or batch processes.
Run batch at other times - night time!
Check that no one is running pointless processes - like programs that loop polling for information.
Check for process that continually output data to a users screen - even when they are not there (like "netscape" and "nmon"!!).
Some AIX services have tunable numbers of daemons like NFS that could be reduced, if not used.
Check for hacker attacks and programs searching through the entire filesystem tree like "find" as these take a lot of CPU and I/O.

Note:

Kernel (wait) is the process the AIX runs when there is absolutely nothing else that can be run (see the PRI field). This is the CPU idle time. If you system is not busy this will be using near 100% CPU. This is normal.

CPU%	Percentage of the last second running on the CPU	You should quickly see which processes are regularly hogging the CPU and if they are sustained or if its small peaks in work.
TIME	Total Time on the CPU	This is tells you if the process is CPU hungry in the longer term.
Difference between SIZE and RES	How much of the program is used regularly	This tells you the size of the code and data actually required to run the currently active services.