70 research outputs found
Towards realistic core-failure-resilient scheduling and analysis
Presented at IEEE Real-Time Systems Symposium (RTSS 2015). 1 to 4, Dec, 2015. San Antonio, U.S.A..Goal: Meeting all task deadlines on a multicore platform even when a core suddenly fails and is rendered unusable.
• Model: When a core fails, whichever task was running there is killed but its deadline must still be me
Assigning real-time tasks on heterogeneous multiprocessors with two types of processors
Consider the problem of scheduling a set of implicitdeadline
sporadic tasks on a heterogeneous multiprocessor
so as to meet all deadlines. Tasks cannot migrate and
the platform is restricted in that each processor is either
of type-1 or type-2 (with each task characterized by a
different speed of execution upon each type of processor).
We present an algorithm for this problem with a timecomplexity
of O(n·m), where n is the number of tasks and
m is the number of processors. It offers the guarantee that
if a task set can be scheduled by any non-migrative algorithm
to meet deadlines then our algorithm meets deadlines
as well if given processors twice as fast. Although this result
is proven for only a restricted heterogeneous multiprocessor,
we consider it significant for being the first realtime
scheduling algorithm to use a low-complexity binpacking
approach to schedule tasks on a heterogeneous
multiprocessor with provably good performance
A conjecture about provably good task assignment on heterogeneous multiprocessor platforms but with a stronger adversary
Consider the problem of scheduling a set of
implicit-deadline sporadic tasks to meet all deadlines on a
heterogeneous multiprocessor platform. We use an algorithm
proposed in [1] (we refer to it as LP-EE) from state-of-the-art
for assigning tasks to heterogeneous multiprocessor platform
and (re-)prove its performance guarantee but for a stronger
adversary.We conjecture that if a task set can be scheduled to
meet deadlines on a heterogeneous multiprocessor platform
by an optimal task assignment scheme that allows task
migrations then LP-EE meets deadlines as well with no
migrations if given processors twice as fast. We illustrate
this with an example
Provably good scheduling of sporadic tasks with resource sharing on a two-type heterogeneous multiprocessor platform
Consider the problem of scheduling a set of implicit-deadline sporadic tasks to meet all deadlines on a two-type
heterogeneous multiprocessor platform where a task may request at most one of |R| shared resources. There are m1
processors of type-1 and m2 processors of type-2. Tasks may migrate only when requesting or releasing resources. We
present a new algorithm, FF-3C-vpr, which offers a guarantee that if a task set is schedulable to meet deadlines by an
optimal task assignment scheme that only allows tasks to migrate when requesting or releasing a resource, then FF-3Cvpr
also meets deadlines if given processors 4+6*ceil(|R|/min(m1,m2)) times as fast. As far as we know, it is the first
result for resource sharing on heterogeneous platforms with provable performance
Provably good task assignment on heterogeneous multiprocessor platforms for a restricted case but with a stronger adversary
Consider the problem of scheduling a set of
implicit-deadline sporadic tasks to meet all deadlines on
a heterogeneous multiprocessor platform. We consider a
restricted case where the maximum utilization of any task on
any processor in the system is no greater than one. We use
an algorithm proposed in [1] (we refer to it as LP-EE) from
state-of-the-art for assigning tasks to heterogeneous multiprocessor
platform and (re-)prove its performance guarantee
for this restricted case but for a stronger adversary. We show
that if a task set can be scheduled to meet deadlines on a
heterogeneous multiprocessor platform by an optimal task
assignment scheme that allows task migrations then LP-EE
meets deadlines as well with no migrations if given processors
twice as fast
Two-type heterogeneous multiprocessor scheduling: Is there a phase transition? (Extended Abstract)
Consider the problem of non-migratively scheduling a set of implicit-deadline sporadic tasks to meet all deadlines on a
two-type heterogeneous multiprocessor platform. We ask the following question: Does there exist a phase transition
behavior for the two-type heterogeneous multiprocessor scheduling problem? We also provide some initial observations
via simulations performed on randomly generated task sets
Intra-type migrative scheduling of implicit-deadline sporadic tasks on two- type heterogeneous multiprocessor
Consider the problem of scheduling a set of implicit-deadline sporadic tasks to meet all deadlines on a two-type
heterogeneous multiprocessor platform. Each processor is either of type-1 or type-2 with each task having different
execution time on each processor type. Jobs can migrate between processors of same type (referred to as intra-type
migration) but cannot migrate between processors of different types. We present a new scheduling algorithm namely,
LP-Relax(THR) which offers a guarantee that if a task set can be scheduled to meet deadlines by an optimal task
assignment scheme that allows intra-type migration then LP-Relax(THR) meets deadlines as well with intra-type
migration if given processors 1/THR as fast (referred to as speed competitive ratio) where THR <= 2/3
CPMD-mindful task assignment for NPS-F
The multiprocessor scheduling scheme NPS-F for sporadic tasks has a high utilisation bound and an overall number of preemptions bounded at design time. NPS-F binpacks tasks offline to as many servers as needed. At runtime, the scheduler ensures that each server is mapped to at most one of the m processors, at any instant. When scheduled, servers use EDF to select which of their tasks to run. Yet, unlike the overall number of preemptions, the migrations per se are not tightly bounded. Moreover, we cannot know a priori which task a server will be currently executing at the instant when it migrates. This uncertainty complicates the estimation of cache-related preemption and migration costs (CPMD), potentially resulting in their overestimation. Therefore, to simplify the CPMD estimation, we propose an amended bin-packing scheme for NPS-F allowing us (i) to identify at design time, which task migrates at which instant and (ii) bound a priori the number of migrating tasks, while preserving the utilisation bound of NPS-F
Considerations on the Least Upper Bound for Mixed-Criticality Real-Time Systems
5th Brazilian Symposium on Computing Systems Engineering, SBESC 2015 (SBESC 2015). 3 to 6, Nov, 2015. Foz do Iguaçu, Brasil.Real-time mixed-criticality systems (MCS) are designed so that tasks with different criticality levels share the same
computing platform. Scheduling mechanisms must ensure that
high criticality tasks are safe independently of lower criticality
tasks’ behaviour. In this paper we provide theoretical schedulability properties for MCS by showing that: (a) the least upper
bound on processor utilisation of MCS is in general null for both
uniprocessor and multiprocessor platforms; (b) this bound lies
in interval [ln 2, 2( √2 − 1)] if higher criticality tasks do not have
periods larger than lower criticality ones; and (c) if the task
of these uniprocessor systems have harmonic periods, the least
upper bound reaches 1
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