Re: Auto Tuning

["trevor perry" <trevorp@xxxxxxxxxxxxxxxx>]

Glenn,

The auto tuner is already collecting data and forecasting - on relatively
recent events. If it were to forecast on the same time this day last week
(and the week before and the week before), it might be improved. However,
experience suggests that usage trends tend not to be consistent, so accurate
proactive forecasting might be hard to accomplish. I do believe there ~is~
an algorithm possible that would allow the auto tuner to work well, but more
than likely, it would take a second iSeries to run the algorithm for the
first...

Actually, I think the auto tuner should be turned off. If it is on, it
should be throttled as much as possible. Given that 99% of performance
problems are application related (yes, that means we write crappy
application code for the most part), the other 99% of performance problems
on most iSeries and AS/400s are caused by poor performance tuning and 99% of
~that~ is caused by the sloppy shipped values and the sloppy auto tuner
values.

I find that performance tuning is truly an art based on scientific
principles. If applied correctly, a performance methodology with human
performance tuning and configuration runs circles around the auto tuner
monkey. Most companies apply no effort to this end. I believe this means
they are not supporting their customers with efficient application of
computing resources. With a well-planned performance methodology, the cost
of the effort is easily recouped with better system throughput.

Mostly, though, performance tuning is a misunderstood science. One simple
example - we all tend to think that we can increase timeslices (for our own
personal benefit, of course), but this is the exact opposite of what should
be done to increase throughput. Timeslices are shipped at the same values
configured for a S/38 model one and should be significantly reduced to
reflect the speed of current processors. If this simple fact is completely
ignored due to misinformation, then there is not much chance that any
iSeries out there will ever be utilized correctly... :-)

Hmmmm. maybe a good auto tuner IS needed...
Stepping off the soapbox now,
Trevor

----- Original Message ----- 
From: "Glenn Ericson"
Subject: Re: Auto Tuning


> Trevor,
> based on your  views, would you  think it a good idea for the auto
> tuner  to save  some stats, and forecast  forward based on trend to be
move
> from reactive to proactive status?