I've seen systems running happily with APC reporting < 10% fragmentation. I know as fragmentation increases performance decreases as APC needs to shuffle things around to find space.
Does anyone have a good rule of thumb as to the percentage of fragmetation you should keep APC below before you can expect overall performance to starts falling off significantly?
If so, at this point, is it a gradual linear drop of performance to fragmentation or does performance falling off a cliff?
Apparently no one knows... I've searched extensively and this is a very 'fuzzy' topic. I can't find benchmarks or tests anywhere regarding this. Just a lot of 'gee, you don't want a lot of fragmentation', without quantifying what 'a lot' means.
I'm going to stick with my gut percentage listed in the question, roughly < 10%.
Eventually, I'm going to run some benchmarks to gather some real data and see if my guess stands ups. I'll add them to this answer if I ever get the time to do them.