Scalable precision cache analysis for real-time software

Staschulat, Jan; Ernst, Rolf

doi:10.1145/1274858.1274863

Cited by 26 publications

(15 citation statements)

References 31 publications

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“…By analyzing the preempted task [10], [11], [12], [13], [14]: Additional misses can only occur for useful cache blocks (UCBs), i.e., blocks that may be cached and that may be reused later, resulting in cache hits. Static analyses have been proposed to safely approximate the set of UCBs.…”

Section: Crpd Analysis For Selfish-lrumentioning

confidence: 99%

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Selfish-LRU: Preemption-aware caching for predictability and performance

Reineke

Altmeyer

Grund

et al. 2014

2014 IEEE 19th Real-Time and Embedded Technology and Applications Symposium (RTAS)

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Abstract-We introduce Selfish-LRU, a variant of the LRU (least recently used) cache replacement policy that improves performance and predictability in preemptive scheduling scenarios.In multitasking systems with conventional caches, a single memory access by a preempting task can trigger a chain reaction leading to a large number of additional cache misses in the preempted task. Selfish-LRU prevents such chain reactions by first evicting cache blocks that do not belong to the currently active task. Simulations confirm that Selfish-LRU reduces the CRPD (cache-related preemption delay) as well as the overall number of cache misses. At the same time, it simplifies CRPD analysis and results in smaller CRPD bounds.

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Section: Crpd Analysis For Selfish-lrumentioning

confidence: 99%

“…By analyzing the preempting task [15], [11], [12], [13]: The preempting task may only cause additional cache misses in those cache sets that it modifies. Thus, analyses to compute bounds on the number of evicting cache blocks (ECBs) have been developed.…”

Section: Crpd Analysis For Selfish-lrumentioning

confidence: 99%

Selfish-LRU: Preemption-aware caching for predictability and performance

Reineke

Altmeyer

Grund

et al. 2014

2014 IEEE 19th Real-Time and Embedded Technology and Applications Symposium (RTAS)

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“…Traditionally, CRPD is computed by analyzing (i) the preempted task [1,9], (ii) the preempting task [19], or (iii) both the preempted and preempting tasks [2,14,17,18]. The concept of useful cache block (UCB) is introduced by [9] for analyzing the preempted task.…”

Section: Related Workmentioning

confidence: 99%

Cache-related preemption delay analysis for FIFO caches

Ballabriga

Chong

Roychoudhury

2014

Proceedings of the 2014 SIGPLAN/SIGBED Conference on Languages, Compilers and Tools for Embedded Systems

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Hard real-time systems are typically composed of multiple tasks, subjected to timing constraints. To guarantee that these constraints will be respected, the Worst-Case Response Time (WCRT) of each task is needed. In the presence of systems supporting preemptible tasks, we need to take into account the time lost due to task preemption. A major part of this delay is the Cache-Related Preemption Delay (CRPD), which represents the penalties due to cache block evictions by preempting tasks. Previous works on CRPD have focused on caches with Least Recently used (LRU) replacement policy. However, for many real-world processors such as ARM9 or ARM11, the use of First-in-first-out (FIFO) cache replacement policy is common.In this paper, we propose an approach to compute CRPD in the presence of instruction caches with FIFO replacement policy. We use the result of a FIFO instruction cache categorization analysis to account for single-task cache misses, and we model as an Integer Linear Programming (ILP) system the additional preemptionrelated cache misses. We study the effect of cache related timing anomalies, our work is the first to deal with the effect of timing anomalies in CRPD computation. We also present a WCRT computation method that takes advantage of the fact that our computed CRPD does not increase linearly with respect to the preemption count. We evaluated our method by computing the CRPD with realistic benchmarks (e.g. drone control application, robot controller application), under various cache configuration parameters. The experimentation shows that our method is able to compute tight CRPD bound for benchmark tasks.

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“…Although the latter (so called "state-based" approach) scales exponentially in space and time in its originally proposed form, it offers high accuracy, which is why this is used as the basis for our proposed approach. Moreover, the authors of [13] have proposed a technique to flexibly scale the complexity of the latter analysis at the expense of precision. The general topic of cache analysis and CRPD computation at a broader perspective is discussed in depth in the following Sec.…”

Section: Related Workmentioning

confidence: 99%

“…[16] considers ECB only, independently of the actually preempted task. In [10,13,14], the CRPD is bounded by considering both UCB and ECB with varying precision. While most proposals limit themselves to direct-mapped caches for the sake of formal simplification, specific problems related to setassociativity have been overlooked or neglected [3] with the consequence of either being unsound or overly pessimistic.…”

Section: Related Workmentioning

confidence: 99%

A synergetic approach to accurate analysis of cache-related preemption delay

Kleinsorge

Falk

Marwedel

2011

Proceedings of the Ninth ACM International Conference on Embedded Software

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The worst-case execution time (WCET) of a task denotes the largest possible execution time for all possible inputs and thus, hardware states. For non-preemptive multitask scheduling, techniques for the static estimation of safe upper bounds have been subject to industrial practice for years. For preemptive scheduling however, the isolated analysis of tasks becomes imprecise as interferences among tasks cannot be considered with sufficient precision. For such scenarios, the cache-related preemption delay (CRPD) denotes a key metric as it reflects the effects of preemptions on the execution behavior of a single task. Until recently, proposals for CRPD analyses were often limited to direct mapped caches or comparably imprecise for k-way set-associative caches.In this paper, we propose how the current best techniques for CRPD analysis, which have only been proposed separately and for different aspects of the analysis can be brought together to construct an efficient CRPD analysis with unique properties. Moreover, along the construction, we propose several different enhancements to the methods employed. We also exploit that in a complete approach, analysis steps are synergetic and can be combined into a single analysis pass solving all formerly separate steps at once. In addition, we argue that it is often sufficient to carry out the combined analysis on basic block bounds, which further lowers the overall complexity. The result is a proposal for a fast CRPD analysis of very high accuracy.

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Scalable precision cache analysis for real-time software

Cited by 26 publications

References 31 publications

Selfish-LRU: Preemption-aware caching for predictability and performance

Selfish-LRU: Preemption-aware caching for predictability and performance

Cache-related preemption delay analysis for FIFO caches

A synergetic approach to accurate analysis of cache-related preemption delay

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