4 research outputs found
The capacity exchange protocol
This paper proposes a new strategy to integrate shared resources and precedence constraints among real-time tasks, assuming
no precise information on critical sections and computation times is available. The concept of bandwidth inheritance
is combined with a capacity sharing and stealing mechanism to efficiently exchange bandwidth among tasks to minimise the
degree of deviation from the ideal system’s behaviour caused by inter-application blocking.
The proposed Capacity Exchange Protocol (CXP) is simpler than other proposed solutions for sharing resources in open
real-time systems since it does not attempt to return the inherited capacity in the same exact amount to blocked servers. This
loss of optimality is worth the reduced complexity as the protocol’s behaviour nevertheless tends to be fair and outperforms
the previous solutions in highly dynamic scenarios as demonstrated by extensive simulations.
A formal analysis of CXP is presented and the conditions under which it is possible to guarantee hard real-time tasks are
discussed
Time-bounded distributed QoS-aware service configuration in heterogeneous cooperative environments
The scarcity and diversity of resources among the devices of heterogeneous computing
environments may affect their ability to perform services with specific Quality
of Service constraints, particularly in dynamic distributed environments where the
characteristics of the computational load cannot always be predicted in advance.
Our work addresses this problem by allowing resource constrained devices to cooperate
with more powerful neighbour nodes, opportunistically taking advantage
of global distributed resources and processing power. Rather than assuming that
the dynamic configuration of this cooperative service executes until it computes
its optimal output, the paper proposes an anytime approach that has the ability
to tradeoff deliberation time for the quality of the solution. Extensive simulations
demonstrate that the proposed anytime algorithms are able to quickly find a good
initial solution and effectively optimise the rate at which the quality of the current
solution improves at each iteration, with an overhead that can be considered
negligible
Dynamic adaptation of stability periods for service level agreements
A QoS adaptation to dynamically changing system conditions
that takes into consideration the user’s constraints
on the stability of service provisioning is presented. The
goal is to allow the system to make QoS adaptation decisions
in response to fluctuations in task traffic flow, under
the control of the user. We pay special attention to the case
where monitoring the stability period and resource load
variation of Service Level Agreements for different types of
services is used to dynamically adapt future stability periods,
according to a feedback control scheme. System’s
adaptation behaviour can be configured according to a desired
confidence level on future resource usage. The viability
of the proposed approach is validated by preliminary
experiments