Reactive Techniques for Controlling Software Speculation

13 years 10 months ago

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Aggressive software speculation holds signiﬁcant potential, because it enables program transformations to reduce the program’s critical path. Like any form of speculation, however, the key to software speculation is employing it only where it is likely to succeed. While mechanisms for controlling hardware speculation (e.g., saturating counters updated after each instance) are well understood, these techniques do not translate directly to software techniques because changing a speculation requires changing the code. As it stands, the dominant software speculation control technique, non-reactive proﬁle-guided optimization, lacks the robustness to support aggressive speculation. The primary thesis of this paper is that software speculation can be made to be robust by adding a reactive controller that can dynamically adjust the speculation. We make two primary observations about such systems: 1) reactive control systems can select behaviors on which to speculate with performance tha...

Craig B. Zilles, Naveen Neelakantam

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