Time-Predictable Computing

Abstract

Abstract. Real-time systems need to be time-predictable in order to prove the timeliness of all their time-critical responses. While this is a well-known fact, recent efforts of the community on concretizing the predictability of task timing have shown that there is no common agreement about what the term timepredictability exactly means. In this paper we propose a universal definition of time-predictability that combines the essence of different discussions about this term. This definition is then instantiated to concrete types of time-predictability, like worst-case execution time (WCET) predictability. Finally, we introduce the concept of a timing barrier as a mechanism for constructing time-predictable systems.

Exploiting Standard Deviation of CPI to Evaluate Architectural Time-Predictability

“…Grund et al [13] then proposed a template for predictability definitions and refined the definition into state-induced time-predictability (SIP) and input-induced time-predictability. Kirner and Puschner [14] formalized a universal definition of time-predictability by combining WCET analyzeability and stability of the system. However, in all the above work, except for that of Grund [12] and Grund et al [13], the calculation for time-predictability is still dependent on the computation of WCET.…”

Is time predictability quantifiable?

“…Kirner and Puschner present several variants of time predictability definitions [11]. The first definition is the interval between the BCET and the WCET: [BCET, WCET], where a smaller interval means better predictable and BCET = WCET considered highest predictability.…”

Architectural time-predictability factor (ATF)

“…Note that several prior studies [1], [10] used estimated WCET to compute time predictability. In this paper, we use static scheduling time instead of WCET.…”

“…Grund et al [9] then proposed a template for predictability definitions and refined the definition into state-induced time predictability and input-induced time predictability. Kirner and Puschner [10] formalized a universal definition of time predictability by combining WCET analyzeability and the stability of the system. However, in all the above work except Grund et al [8], [9], the calculation of time predictability is still dependent on the computation of WCET.…”