|
Categories
|
Description
|
Example
(File system simulator)
|
|
Category1: Single action applicable
|
The system states in this category are
such that only a single candidate action is applicable, i.e., searching the
specifications leads to a single candidate action
|
Workload: Sequential, read dominated with
read/write ratio of 0.9, avg. queue-depth = 6 Current Throughput = 80 MBps Goal = 100 MBps Polus specification search: The only action that
becomes applicable is Prefetching.
|
|
Category 2: Multiple actions applicable
(they appear to have similar preconditions and/or implications)
|
In this category more than one action have similar preconditions and/or implications and are
indistinguishable. In reality, these actions are not similar This category
becomes increasingly common during initial bootstrapping, i.e., the system
hasn't learnt values for preconditions and implications
|
Workload: Read dominated,
sequential/random ratio = 0.2, average queue-depth = 8. Current Throughput
= 80 MBps Goal = 100 MBps
Polus specification search: Prefetching
and Replication are selected as candidate actions. In reality Prefetching is not applicable as the workload is not
sequential, but Polus does not have the threshold
value for the sequential/random ratio in prefetch
specifications
|
|
Category 3: More than one goal not met
|
In this category, more than one action
needs to be invoked as a single action cannot satisfy the goal requirements
|
Workload: Sequential, read/write= 0.3 Current
Throughput = 80 MBps Goal = 100 MBps , Current Latency = 6msec Goal = 4.5 msec Polus specification
search: Prefetching and Clean delay are both
invoked as the former improves throughput while the later improves latency
|
|
Category 4: Recurrent action invocation
(One action, leads to chaininvocation of actions)
|
In this category, invocation of an action
leads to a chain-invocation of a series of actions. Ability to detect and
prevent recurrent action invocation is a required property of the management
software
|
Workload: Trigger for data backup with
window = 4 hours Polus specification search:
Theoretically, backup can be invoked since the goals are being met. But
invoking backup at this time will cause latency goals to be overshot
|
|
Category 5: No action applicable
(Negation of previous actions required)
|
Actions are negated under two scenarios:
to make resources available for another actions, and the workload
preconditions change
|
Workload: Changes from large block
sequential to small block random Polus
specification search: Prefetching hurts
performance as memory and storage resources are used for acquiring data
that is never used
|
