The first year of the COBS project was largely spent creating the basic object
system and infrastructure. Many efforts now are directed towards evaluating
and refining the use of COBS's configuation mechanisms and techniques.
The understanding gained from the process will be used to judge the
suitability and flexibility of the COBS mechanisms as well as to evaluate the
types of configurability that can be exploited at various levels of the COBS
system. In particular, the following efforts are in progres:
Performance evaluation of the object caching prototype is under way. We have
implemented a sophisticated synthetic workload generator based on large scale
distributed file system traces from Princeton University and
traces from a wide area industrial file system. The workload
generator takes into account factors such as file inertia, file entropy,
temporal locality, read-write sharing within and among clusters. Initial
results of the evaluation corroborate our hypothesis. This is an example of
horizontal use of configuration attributes. That is, use of characteristics
on one side of an exchange being used to configure the behavior of a similar
level on the opposite side of an exchange.
We are also proceeding with a variety of vertical configuration
experiments, in which lower levels benefit from application-level information.
One example of the use of application-level information is in a fast ATM
protocol we are developing. In situations where buffer requirements can be
predicted, this protocol implements a zero-copy ATM receive operation by
depositing incoming messages directly into user address space.
Other vertical configuration efforts include the ability to select from
a variety of network transport mechanisms for different object invocations, to
adjust and specify protocol-level quality of service requirements, use of
application-level information to control encryption/decryption or
compression/uncompression, and configurability for dynamic communications
resource management in order to maximize throughput.
