Testing autonomous navigation algorithms of Unmanned Aerial Vehicles (UAVs) in real-world scenarios often entails significant safety risks. In this paper, we aim to build a flexible yet user-friendly UAV autonomous navigation simulator. Ideally, it should closely emulate real-world environments, support diverse UAV models and algorithms, and provide a flexible evaluation framework. Existing frameworks fail to satisfy all three requirements simultaneously. To this end, we present AirNavigation, an integrated simulation platform designed to support the end-to-end workflow of UAV navigation research. Specifically, our system leverages Unreal Engine to simulate highly realistic environments and diverse UAV models. It further facilitates semi-automated scene generation and multi-modal synthetic training data production. To lower the barrier of adoption, we develop a suite of user-friendly interfaces to enable seamless integration of diverse navigation algorithms. Moreover, we introduce a novel evaluation system powered by large language models to deliver personalized and fine-grained performance analysis.

As the foundational component of versatile AI applications, training an multimodal large language model (MLLM) relies on multimodal datasets with dynamic modality mixture proportions and sample length distributions. However, existing MLLM systems remain inefficient under dynamic workloads, due to statically coupled decisions of resource allocation and model parallelization between encoders and the LLM backbone. This paper presents MegaScale-Omni, an industrial-grade MLLM training system tailored for dynamic workload adaption and hyper-scale deployment. MegaScale-Omni is built upon the training scheme of encoder-LLM multiplexing with three key innovations: (1) Decoupled parallelism strategies with long-short sequence parallelism for encoders to process variable-length samples, and full-fledged 5D parallelism for the LLM backbone, both organized under a communication-efficient parallelization layout. (2) Unified encoder-LLM representations for flexible, extensible colocation, and a new paradigm of encoder-LLM joint pipeline with workload resilience. (3) Workload balancing techniques via decentralized grouped reordering in data loaders and adaptive resharding from encoder to LLM ranks. MegaScale-Omni is deployed as the foundation of our in-house large-scale MLLM training tasks with thousands of GPUs. Our experimental results demonstrate 1.27×–7.57× throughput improvement under production-grade dynamic workloads, as compared to four state-of-the-art systems.

Modern frameworks for training large foundation models (LFMs) employ dataloaders in a data-parallel manner, with each loader processing a disjoint subset of training data. When preparing data for LFM training that originates from multiple, distinct sources, two fundamental challenges arise. First, due to the quadratic computational complexity of the attention operator, the non-uniform sample distribution over data-parallel ranks leads to significant workload imbalance among dataloaders, degrading the training efficiency. Second, supporting diverse data sources requires per-dataset file access states that are redundantly replicated across parallel loaders, consuming excessive memory. This also hinders dynamic data mixing (e.g., curriculum learning) and causes redundant access/memory overhead in hybrid parallelism.

The development of multi-modal Unmanned Aerial Vehicles (UAVs) environment perception systems is hindered by three critical gaps in existing datasets: (1) insufficient modalities and pixel misalignment, (2) noisy labels, and (3) limited task types. To address these gaps, we propose an automatic data construction approach and construct a multi-modal UAV-based environment perception dataset, UEMM-Air. Its synthetic nature ensures scalability, reproducibility, and rare-event coverage, making it suitable for large-scale model pre-training. Benefiting from our automated data collection and annotation pipeline, UEMM-Air encompasses 120k data pairs across 6 aligned modalities and supports 4 perception tasks, significantly exceeding existing datasets (max 60k data, 3 modalities, 2 tasks). Compared to existing synthetic datasets like SynDrone, UEMM-Air provides more accurate annotations by avoiding noisy labels from direct coordinate computation. Notably, models pre-trained on UEMM-Air achieve a 5.8% accuracy improvement compared to those utilizing other synthetic datasets, while requiring less than half the data. This benchmark establishes performance evaluation of UAV multi-modal environmental perception models, and hopefully encourages more research efforts towards enabling UAVs to undertake more multi-modal tasks. The dataset and its generation engine are openly accessible under a permissive license at https://github.com/1e12Leon/UEMM-Air.

Efficiently training large language models (LLMs) on commodity cloud resources remains challenging due to limitations in network bandwidth and accelerator memory capacity. Existing training systems can be categorized based on their pipeline schedules. Depth-first scheduling, employed by systems like Megatron, prioritizes memory efficiency but restricts the overlap between communication and computation, causing accelerators to remain idle for over 20% of the training time. Conversely, breadth-first scheduling maximizes communication overlap but generates excessive intermediate activations, exceeding memory capacity and slowing computation by more than 34%. To address these limitations, we propose a novel elastic pipeline schedule that enables fine-grained control over the trade-off between communication overlap and memory consumption. Our approach determines the number of micro-batches scheduled together according to the communication time and the memory available. Furthermore, we introduce a mixed sharding strategy and a pipeline-aware selective recomputation technique to reduce memory usage. Experimental results demonstrate that our system eliminates most of the 28% all-accelerator idle time caused by communication, with recomputation accounting for less than 1.9% of the training time. Compared to existing baselines,PIPEMESHimproves training throughput on commodity clouds by 20.1% to 33.8%.

The blockchain paradigm has attracted diverse applications to be deployed upon. However, no service-level agreement (SLA) mechanism has been proposed to enforce the SLA disseminating deadlines to commit blockchain transactions, although these transactions are often interactively submitted by clients and desire short SLA deadlines (e.g., tens of seconds). Existing peer-to-peer (P2P) multicast protocols for blockchains take the unidirectional approach to disseminate transactions regardless of their SLA deadlines, making transactions easily violate their deadlines. Moreover, these protocols are vulnerable to malicious P2P nodes, and their protocol messages (e.g., SLAstringent transactions) are vulnerable to deferring attacks. We propose SLARM, the first bidirectional P2P multicast protocol for permissioned blockchains, which conservatively adjusts transactions' dissemination speed to satisfy their SLA deadlines according to the trustworthy SLA feedback of previously disseminated transactions. SLARM guarantees transactions' SLAs in a decentralized way and defends against the deferring attacks using TEE. Evaluation of SLARM with five notable P2P multicast protocols and five diverse real-world applications shows that: even with transaction spikes and attacked nodes, SLARM achieves a much higher transaction SLA satisfaction rate with reasonably high commit throughput.

With the trend of processing a large volume of sensitive data on PaaS services (e.g., DNN training), a TEE architecture that supports general heterogeneous accelerators, enables spatial sharing on one accelerator, and enforces strong isolation across accelerators is highly desirable. However, none of the existing TEE solutions meet all three requirements. In this paper, we propose CRONUS, the first TEE architecture that achieves the three crucial requirements. The key idea of CRONUS is to partition heterogeneous computation into isolated TEE enclaves, where each enclave encapsulates only one kind of computation (e.g., GPU computation), and multiple enclaves can spatially share an accelerator. Then, CRONUS constructs heterogeneous computing using remote procedure calls (RPCs) among enclaves. With CRONUS, each accelerator’s hardware and its software stack are strongly isolated from others’, and each enclave trusts only its own hardware. To tackle the security challenge caused by inter-enclave interactions, we design a new streaming remote procedure call abstraction to enable secure RPCs with high performance. CRONUS is software-based, making it general to diverse accelerators. We implemented CRONUS on ARM TrustZone. Evaluation on diverse workloads with CPUs, GPUs and NPUs shows that, CRONUS achieves less than 7.1% extra computation time compared to native (unprotected) executions.

Existing tools to detect side-channel attacks on Intel SGX are grounded on the observation that attacks affect the performance of the victim application. As such, all detection tools monitor the potential victim and raise an alarm if the witnessed performance (in terms of runtime, enclave interruptions, cache misses, etc.) is out of the ordinary.

Traditional anonymous networks (e.g., Tor) are vulnerable to traffic analysis attacks that monitor the whole network traffic to determine which users are communicating. To preserve user anonymity against traffic analysis attacks, the emerging mix networks mess up the order of packets through a set of centralized and explicit shuffling nodes. However, this centralized design of mix networks is insecure against targeted DoS attacks that can completely block these shuffling nodes. In this article, we presentDAENet, an efficient mix network that resists both targeted DoS attacks and traffic analysis attacks with a new abstraction calledStealthy Peer-to-Peer (P2P) Network. Thestealthy P2P networkeffectively hides the shuffling nodes used in a routing path into the whole network, such that adversaries cannot distinguish specific shuffling nodes and conduct targeted DoS attacks to block these nodes. In addition, to handle traffic analysis attacks, we leverage the confidentiality and integrity protection of Intel SGX to ensure trustworthy packet shuffles at each distributed host and use multiple routing paths to prevent adversaries from tracking and revealing user identities. We show that our system is scalable with moderate latency (2.2s) when running in a cluster of 10,000 participants and is robust in the case of machine failures, making it an attractive new design for decentralized anonymous communication. DAENet ’s code is released onhttps://github.com/hku-systems/DAENet.

The increasing computational complexity of DNNs achieved unprecedented successes in various areas such as machine vision and natural language processing (NLP), e.g., the recent advanced Transformer has billions of parameters. However, as large-scale DNNs significantly exceed GPU's physical memory limit, they cannot be trained by conventional methods such as data parallelism. Pipeline parallelism that partitions a large DNN into small subnets and trains them on different GPUs is a plausible solution. Unfortunately, the layer partitioning and memory management in existing pipeline parallel systems are fixed during training, making them easily impeded by out-of-memory errors and the GPU under-utilization. These drawbacks amplify when performing neural architecture search (NAS) such as the evolved Transformer, where different network architectures of Transformer needed to be trained repeatedly. vPipe is the first system that transparently provides dynamic layer partitioning and memory management for pipeline parallelism. vPipe has two unique contributions, including (1) an online algorithm for searching a near-optimal layer partitioning and memory management plan, and (2) a live layer migration protocol for re-balancing the layer distribution across a training pipeline. vPipe improved the training throughput of two notable baselines (Pipedream and GPipe) by 61.4-463.4 percent and 24.8-291.3 percent on various large DNNs and training settings.

A distributed database utilizing the wide-spread edge computing servers to provide low-latency data access with the serializability guarantee is highly desirable for emerging edge computing applications. In an edge database, nodes are divided into regions, and a transaction can be categorized as intra-region (IRT) or cross-region (CRT) based on whether it accesses data in different regions. In addition to serializability, we insist that a practical edge database should provide low tail latency for both IRTs and CRTs, and such low latency must be scalable to a large number of regions. Unfortunately, none of existing geo-replicated serializable databases or edge databases can meet such requirements.

A permissioned blockchain framework typically runs an efficient Byzantine consensus protocol and is attractive to deploy fast trading applications among a large number of mutually untrusted participants (e.g., companies). Unfortunately, all existing permissioned blockchain frameworks adopt sequential workflows for invoking the consensus protocol and executing applications' transactions, making the performance of these applications much lower than deploying them in traditional systems (e.g., in-datacenter stock exchange).

Applications written in Java have strengths to tackle diverse threats in public clouds, but these applications are still prone to privileged attacks when processing plaintext data. Intel SGX is powerful to tackle these attacks, and traditional SGX systems rewrite a Java application's sensitive functions, which process plaintext data, using C/C++ SGX API. Although this code-rewrite approach achieves good efficiency and a small TCB, it requires SGX expert knowledge and can be tedious and error-prone. To tackle the limitations of rewriting Java to C/C++, recent SGX systems propose a code-reuse approach, which runs a default JVM in an SGX enclave to execute the sensitive Java functions. However, both recent study and this paper find that running a default JVM in enclaves incurs two major vulnerabilities, Iago attacks, and control flow leakage of sensitive functions, due to the usage of OS features in JVM. In this paper, Uranus creates easy-to-use Java programming abstractions for application developers to annotate sensitive functions, and Uranus automatically runs these functions in SGX at runtime. Uranus effectively tackles the two major vulnerabilities in the code-reuse approach by presenting two new protocols: 1) a Java bytecode attestation protocol for dynamically loaded functions; and 2) an OS-decoupled, efficient GC protocol optimized for data-handling applications running in enclaves. We implemented Uranus in Linux and applied it to two diverse data-handling applications: Spark and ZooKeeper. Evaluation shows that: 1) Uranus achieves the same security guarantees as two relevant SGX systems for these two applications with only a few annotations; 2) Uranus has reasonable performance overhead compared to the native, insecure applications; and 3) Uranus defends against privileged attacks. Uranus source code and evaluation results are released on https://github.com/hku-systems/uranus.

In the era of big-data, individuals and institutions store their sensitive data on clouds, and these data are often analyzed and computed by MapReduce frameworks (e.g., Spark). However, releasing the computation result on these data may leak privacy. Differential Privacy (DP) is a powerful method to preserve the privacy of an individual data record from a computation result. Given an input dataset and a query, DP typically perturbs an output value with noise proportional to sensitivity, the greatest change on an output value when a record is added to or removed from the input dataset. Unfortunately, directly computing the sensitivity value for a query and an input dataset is computationally infeasible, because it requires adding or removing every record from the dataset and repeatedly running the same query on the dataset: a dataset of one million input records requires running the same query for more than one million times. This paper presents UPA, the first automated, accurate, and efficient sensitivity inferring approach for big-data mining applications. Our key observation is that MapReduce operators often have commutative and associative properties in order to enable parallelism and fault tolerance among computers. Therefore, UPA can greatly reduce the repeated computations at runtime while computing a precise sensitivity value automatically for general big-data queries. We compared UPA with FLEX, the most relevant work that does static analysis on queries to infer sensitivity values. Based on an extensive evaluation on nine diverse Spark queries, UPA supports all the nine evaluated queries, while FLEX supports only five of the nine queries. For the five queries which both UPA and FLEX can support, UPA enforces DP with five orders of magnitude more accurate sensitivity values than FLEX. UPA has reasonable performance overhead compared to native Spark. UPA's source code is available on https://github.com/hku-systems/UPA.

Big-data frameworks (e.g., Spark) enable computations on tremendous data records generated by third parties, causing various security and reliability problems such as information leakage and programming bugs. Existing systems for big-data security (e.g., Titian) track data transformations in a record level, so they are imprecise and too coarse-grained for these problems. For instance, when we ran Titian to drill down input records that produced a buggy output record, Titian reported 3 to 9 orders of magnitude more input records than the actual ones. Information Flow Tracking (IFT) is a conventional approach for precise information control. However, extant IFT systems are neither efficient nor complete for big-data frameworks, because theses frameworks are data-intensive, and data flowing across hosts is often ignored by IFT.

State machine replication (SMR) uses Paxos to enforce the same inputs for a program (e.g., Redis) replicated on a number of hosts, tolerating various types of failures. Unfortunately, traditional Paxos protocols incur prohibitive performance overhead on server programs due to their high consensus latency on TCP/IP. Worse, the consensus latency of extant Paxos protocols increases drastically when more concurrent client connections or hosts are added. This paper presents APUS, the first RDMA-based Paxos protocol that aims to be fast and scalable to client connections and hosts. APUS intercepts inbound socket calls of an unmodified server program, assigns a total order for all input requests, and uses fast RDMA primitives to replicate these requests concurrently.