Typical Performance Trade-Offs

As processor overhead increases, the delay budget increases. As flexibility increases,
delay variability increases: The OS allows more interrupts, since more control and
choice to the user increases interrupt overheads. The delay and delay variability introduced
by the application layer OS becomes, as we will show, a major part of the endto-
end delay and jitter (delay variability) budget. If we are judging quality on the basis
of end-to-end delay and end-to-end delay variability, then application layer software
response times become a critical performance metric.
We also have to qualify how well the software coexists with the target hardware
platform. The more deeply we embed software, the more remote we make the software
from the outside world, the more deterministic we can make software performance—
that is, the better we can manage delay and delay variability. However the more deeply
embedded the software, the less flexible it becomes; the outside world cannot influence
the software and therefore has no control over it.