2,282 research outputs found
Resource management for extreme scale high performance computing systems in the presence of failures
2018 Summer.Includes bibliographical references.High performance computing (HPC) systems, such as data centers and supercomputers, coordinate the execution of large-scale computation of applications over tens or hundreds of thousands of multicore processors. Unfortunately, as the size of HPC systems continues to grow towards exascale complexities, these systems experience an exponential growth in the number of failures occurring in the system. These failures reduce performance and increase energy use, reducing the efficiency and effectiveness of emerging extreme-scale HPC systems. Applications executing in parallel on individual multicore processors also suffer from decreased performance and increased energy use as a result of applications being forced to share resources, in particular, the contention from multiple application threads sharing the last-level cache causes performance degradation. These challenges make it increasingly important to characterize and optimize the performance and behavior of applications that execute in these systems. To address these challenges, in this dissertation we propose a framework for intelligently characterizing and managing extreme-scale HPC system resources. We devise various techniques to mitigate the negative effects of failures and resource contention in HPC systems. In particular, we develop new HPC resource management techniques for intelligently utilizing system resources through the (a) optimal scheduling of applications to HPC nodes and (b) the optimal configuration of fault resilience protocols. These resource management techniques employ information obtained from historical analysis as well as theoretical and machine learning methods for predictions. We use these data to characterize system performance, energy use, and application behavior when operating under the uncertainty of performance degradation from both system failures and resource contention. We investigate how to better characterize and model the negative effects from system failures as well as application co-location on large-scale HPC computing systems. Our analysis of application and system behavior also investigates: the interrelated effects of network usage of applications and fault resilience protocols; checkpoint interval selection and its sensitivity to system parameters for various checkpoint-based fault resilience protocols; and performance comparisons of various promising strategies for fault resilience in exascale-sized systems
On the complexity of scheduling checkpoints for computational workflows
This paper deals with the complexity of scheduling computational workflows in the presence of Exponential failures. When such a failure occurs, rollback and recovery is used so that the execution can resume from the last checkpointed state. The goal is to minimize the expected execution time, and we have to decide in which order to execute the tasks, and whether to checkpoint or not after the completion of each given task. We show that this scheduling problem is strongly NP-complete, and propose a (polynomial-time) dynamic programming algorithm for the case where the application graph is a linear chain. These results lay the theoretical foundations of the problem, and constitute a prerequisite before discussing scheduling strategies for arbitrary DAGS of moldable tasks subject to general failure distributions
On the impact of process replication on executions of large-scale parallel applications with coordinated checkpointing
International audienceProcessor failures in post-petascale parallel computing platforms are common occurrences. The traditional fault-tolerance solution, checkpoint-rollback-recovery, severely limits parallel efficiency. One solution is to replicate application processes so that a processor failure does not necessarily imply an application failure. Process replication, combined with checkpoint-rollback-recovery, has been recently advocated. We first derive novel theoretical results for Exponential failure distributions, namely exact values for the Mean Number of Failures To Interruption and the Mean Time To Interruption. We then extend these results to arbitrary failure distributions, obtaining closed-form solutions for Weibull distributions. Finally, we evaluate process replica-tion in simulation using both synthetic and real-world failure traces so as to quantify average application makespan. One interesting result from these experiments is that, when process repli-cation is used, application performance is not sensitive to the checkpointing period, provided that that period is within a large neighborhood of the optimal period. More generally, our empirical results make it possible to identify regimes in which process replication is beneficial
Reliable Provisioning of Spot Instances for Compute-intensive Applications
Cloud computing providers are now offering their unused resources for leasing
in the spot market, which has been considered the first step towards a
full-fledged market economy for computational resources. Spot instances are
virtual machines (VMs) available at lower prices than their standard on-demand
counterparts. These VMs will run for as long as the current price is lower than
the maximum bid price users are willing to pay per hour. Spot instances have
been increasingly used for executing compute-intensive applications. In spite
of an apparent economical advantage, due to an intermittent nature of biddable
resources, application execution times may be prolonged or they may not finish
at all. This paper proposes a resource allocation strategy that addresses the
problem of running compute-intensive jobs on a pool of intermittent virtual
machines, while also aiming to run applications in a fast and economical way.
To mitigate potential unavailability periods, a multifaceted fault-aware
resource provisioning policy is proposed. Our solution employs price and
runtime estimation mechanisms, as well as three fault tolerance techniques,
namely checkpointing, task duplication and migration. We evaluate our
strategies using trace-driven simulations, which take as input real price
variation traces, as well as an application trace from the Parallel Workload
Archive. Our results demonstrate the effectiveness of executing applications on
spot instances, respecting QoS constraints, despite occasional failures.Comment: 8 pages, 4 figure
Improving Parallel I/O Performance Using Interval I/O
Today\u27s most advanced scientific applications run on large clusters consisting of hundreds of thousands of processing cores, access state of the art parallel file systems that allow files to be distributed across hundreds of storage targets, and utilize advanced interconnections systems that allow for theoretical I/O bandwidth of hundreds of gigabytes per second. Despite these advanced technologies, these applications often fail to obtain a reasonable proportion of available I/O bandwidth. The reasons for the poor performance of application I/O include the noncontiguous I/O access patterns used for scientific computing, contention due to false sharing, and the somewhat finicky nature of parallel file system performance. We argue that a more fundamental cause of this problem is the legacy view of a file as a linear sequence of bytes. To address these issues, we introduce a novel approach for parallel I/O called Interval I/O. Interval I/O is an innovative approach that uses application access patterns to partition a file into a series of intervals, which are used as the fundamental unit for subsequent I/O operations. Use of this approach provides superior performance for the noncontiguous access patterns which are frequently used by scientific applications. In addition, the approach reduces false contention and the unnecessary serialization it causes. Interval I/O also significantly increases the performance of atomic mode operations. Finally, the Interval I/O approach includes a technique for supporting parallel I/O for cooperating applications. We provide a prototype implementation of our Interval I/O system and use it to demonstrate performance improvements of as much as 1000% compared to ROMIO when using Interval I/O with several common benchmarks
Operating policies for energy efficient large scale computing
PhD ThesisEnergy costs now dominate IT infrastructure total cost of ownership, with datacentre
operators predicted to spend more on energy than hardware infrastructure in the
next five years. With Western European datacentre power consumption estimated at
56 TWh/year in 2007 and projected to double by 2020, improvements in energy efficiency
of IT operations is imperative. The issue is further compounded by social and
political factors and strict environmental legislation governing organisations.
One such example of large IT systems includes high-throughput cycle stealing distributed
systems such as HTCondor and BOINC, which allow organisations to leverage
spare capacity on existing infrastructure to undertake valuable computation.
As a consequence of increased scrutiny of the energy impact of these systems, aggressive
power management policies are often employed to reduce the energy impact
of institutional clusters, but in doing so these policies severely restrict the computational
resources available for high-throughput systems. These policies are often configured
to quickly transition servers and end-user cluster machines into low power
states after only short idle periods, further compounding the issue of reliability.
In this thesis, we evaluate operating policies for energy efficiency in large-scale
computing environments by means of trace-driven discrete event simulation, leveraging
real-world workload traces collected within Newcastle University.
The major contributions of this thesis are as follows:
i) Evaluation of novel energy efficient management policies for a decentralised
peer-to-peer (P2P) BitTorrent environment.
ii) Introduce a novel simulation environment for the evaluation of energy efficiency
of large scale high-throughput computing systems, and propose a generalisable
model of energy consumption in high-throughput computing systems.
iii
iii) Proposal and evaluation of resource allocation strategies for energy consumption
in high-throughput computing systems for a real workload.
iv) Proposal and evaluation for a realworkload ofmechanisms to reduce wasted task
execution within high-throughput computing systems to reduce energy consumption.
v) Evaluation of the impact of fault tolerance mechanisms on energy consumption
DynaQuant: Compressing Deep Learning Training Checkpoints via Dynamic Quantization
With the increase in the scale of Deep Learning (DL) training workloads in
terms of compute resources and time consumption, the likelihood of encountering
in-training failures rises substantially, leading to lost work and resource
wastage. Such failures are typically offset by a checkpointing mechanism, which
comes at the cost of storage and network bandwidth overhead. State-of-the-art
approaches involve lossy model compression mechanisms, which induce a tradeoff
between the resulting model quality (accuracy) and compression ratio. Delta
compression is then used to further reduce the overhead by only storing the
difference between consecutive checkpoints. We make a key enabling observation
that the sensitivity of model weights to compression varies during training,
and different weights benefit from different quantization levels (ranging from
retaining full precision to pruning). We propose (1) a non-uniform quantization
scheme that leverages this variation, (2) an efficient search mechanism that
dynamically finds the best quantization configurations, and (3) a
quantization-aware delta compression mechanism that rearranges weights to
minimize checkpoint differences, thereby maximizing compression. We instantiate
these contributions in DynaQuant - a framework for DL workload checkpoint
compression. Our experiments show that DynaQuant consistently achieves a better
tradeoff between accuracy and compression ratios compared to prior works,
enabling a compression ratio up to 39x and withstanding up to 10 restores with
negligible accuracy impact for fault-tolerant training. DynaQuant achieves at
least an order of magnitude reduction in checkpoint storage overhead for
training failure recovery as well as transfer learning use cases without any
loss of accuracy
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