An Efficient Analysis of Worst Case Flush Timings for Branch Predictors

Konishi, Masahiro; Nakada, Takashi; Tsumura, Tomoaki; Nakashima, Hiroshi; Takada, Hiroaki

doi:10.2197/ipsjdc.3.255

Cited by 1 publication

(1 citation statement)

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“…The worst case values of a branch direction predictor, which does not have such apparent ones, can be approximated by an O(N ) simple algorithm presented in Ref. 5). Note that a pair of executions with different interruption points, namely i n and i n (n < n ), should have different microarchitectural states at the fetch of i n +1 , because the latter's has been just flushed while the former has something resulted from the execution of i n+1 , .…”

Section: Models Of Processor and Interruptionmentioning

confidence: 99%

A Simulation-Based Analysis for Worst Case Delay of Single and Multiple Interruptions

Nakashima

Konishi²,

Nakada

2008

IPSJ Transactions on System LSI Design Methodology

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This paper proposes an efficient method to analyze the worst case interruption delay (WCID) of a workload running on modern microprocessors using a cycle accurate simulator (CAS). Our method is highly accurate because it simulates all possible cases inserting an interruption just before the retirement of every instruction executed in a workload. It is also (reasonably) efficient because it takes O(N log N ) time for a workload with N executed instructions, instead of O(N 2 ) of a straightforward iterative simulation of interrupted executions. The key idea for the efficiency is that a pair of executions with different interruption points has a set of durations in which they behave exactly coherent and thus one of simulations for the durations may be omitted. We implemented this method modifying the SimpleScalar tool set to prove it finds out WCID of workloads with five million executed instructions in reasonable time, less than 30 minutes, which would be 200-300 days by the straightforward method. Furthermore, our CAS-based analyzer may have a post process to calculate the WCID for multiple F interrupts with O(F N √ N log N ) time complexity.

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Section: Models Of Processor and Interruptionmentioning

confidence: 99%