2004 IEEE International Symposium on Performance Analysis of Systems and Software (ISPASS'04) Deconstructing commit Austin, TX, USA March 10-March 12 ISBN: 0-7803-8385-0
Many modern processors execute instructions out of their original program order to exploit instruction-level parallelism and achieve higher performance. However even though instructions can execute in an arbitrary order, they must eventually commit, or retire from execution, in program order. This constraint provides a safety mechanism to ensure that mis-speculated instructions are not inadvertently committed, but can consume valuable processor resources and severely limit the degree of parallelism exposed in a program. We assert that such a constraint is overly conservative, and propose conditions under which it can be relaxed. This paper deconstructs the notion of commit in an out-of-order processor, and examines the set of necessary conditions under which instructions can be permitted to retire out of program order. It provides a detailed analysis of the frequency and relative importance of these conditions, and discusses microarchitectural modifications that relax the in-order commit requirement. Overall, we found that for a given set of processor resources our technique achieves speedups of up to 68% and 8% for floating point and integer benchmarks, respectively. Conversely, because out-of-order commit allows more efficient utilization of cycle-time limiting resources, it can alternatively enable simpler designs with potentially higher clock frequencies.
Citation:
G.B. Bell, M.H. Lipasti, "Deconstructing commit," ispass, pp.68-77, 2004 IEEE International Symposium on Performance Analysis of Systems and Software (ISPASS'04), 2004 Usage of this product signifies your acceptance of the Terms of Use. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||