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arXiv · 2026
QFabric：在Linux-RTOS板上的受保护跨域任务恢复及其局限性
Ayushman Bhattacharya, Anwesha Chakraborty
Heterogeneous embedded boards pair a Linux application processor with a real-time microcontroller (MCU), which suggests moving a task between the two domains when its timing degrades. We present QFabric, a prototype that treats cross-domain placement as guarded recovery from a violated empirical soft real-time contract: a bounded task is compiled for both domains, monitored in windows with hysteresis, switched only after semantic and capacity admission at a quiescent epoch boundary, and committed or rolled back after probation. On an Arduino UNO Q (Cortex-A53 Linux and a Cortex-M33 running Zephyr), we characterize the stock Bridge RPC interconnect and measure five workloads in both domains under idle, CPU-load, and higher-priority SCHED_FIFO contention, with ordinary and real-time callers. Each MCU invocation costs about 19 ms of dispatch regardless of compute, the MCU runs the heaviest kernel 34x slower, and because every call traverses Linux userspace, Linux contention inflates the MCU path far more than the Linux path (p99 up to 400 ms versus 17.0 ms). Across 30 cells of a four-node chain, Linux meets every contract within 0.8% misses and QFabric correctly never migrates; a controller without hysteresis migrates in 7 cells, raising p95 by up to 177x, and probation rolls back 5 of those moves. On Linux-dispatched heterogeneous boards, migration therefore cannot isolate a task from Linux interference, and recovery guards matter chiefly by preventing harmful moves. This paper supersedes an earlier artifact release whose reported improvement arose from measurement defects that we identify. All source, raw traces, and generators are public.
异构嵌入式板卡将Linux应用处理器与实时微控制器（MCU）配对，这暗示着当任务的时序性能下降时，可以将其在两个域之间迁移。我们提出了QFabric，一个将跨域放置视为受保护恢复的原型，即从被违反的经验性软实时契约中恢复：一个有界任务被编译到两个域，在带滞后的窗口中监控，仅在静默纪元边界处通过语义和容量准入后才切换，并在试用期后提交或回滚。在Arduino UNO Q（Cortex-A53 Linux和运行Zephyr的Cortex-M33）上，我们表征了原装Bridge RPC互连，并在空闲、CPU负载和更高优先级SCHED_FIFO争用下，使用普通调用者和实时调用者，在两个域中测量了五种工作负载。每次MCU调用无论计算量如何，调度开销约为19毫秒，MCU运行最重的内核慢34倍，并且由于每次调用都经过Linux用户空间，Linux争用对MCU路径的膨胀远大于Linux路径（p99高达400毫秒对17.0毫秒）。在四节点链的30个单元中，Linux满足所有契约，未命中率在0.8%以内，QFabric正确地从不迁移；没有滞后的控制器在7个单元中发生迁移，将p95最多提高177倍，试用期回滚了其中5次迁移。因此，在Linux调度的异构板卡上，迁移无法将任务与Linux干扰隔离，恢复保护措施的主要作用在于防止有害迁移。本文取代了早期的制品发布，其报告的改进源于我们已识别的测量缺陷。所有源代码、原始跟踪和生成器均已公开。
PDF · 2026年11月翻译