The Leland & Ott 1986 Model
This is actually a model of process runtimes in an interactive
environment, rather than a model of a parallel workload.
Its distinction lies in the innovative functional form used to
describe the distribution.
The proposed distribution is valid for processes that are longer than
With this restriction, the probability that a process will run for
more than t seconds is proportional to tk,
with k in the range -1.25 < k < -1.05.
A subsequent study by Harchol-Balter and Downey reaffirmed this model,
and provided the following formulae:
- k in the range -1.3 < k < -.8, with k = -1
a reasonable default.
- Prob(runtime > t sec | runtime > 1 sec) = tk
For k = -1, this is 1 / t.
- Prob(runtime = t sec | age = 1 sec) = -k tk-1
For k = -1, this is 1 / t2.
This model is described in the following papers:
Parallel Workloads Archive - Models