Browsing by Author "Tulika MITRA"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Modeling Out-of-Order Processors for Software Timing Analysis
    (2004-08-01T00:00:00Z) Xianfeng LI; Abhik ROYCHOUDHURY; Tulika MITRA
    Estimating the Worst Case Execution Time (WCET) of a program on a given processor is important for the schedulability analysis of real-time systems. WCET analysis techniques typically model the timing effects of microarchitectural features in modern processors (such as the pipeline, caches, branch prediction, etc.) to obtain safe but tight estimates. In this paper, we model out-of-order processor pipelines for WCET analysis. This analysis is, in general, difficult even for a basic block (a sequence of instructions with single-entry and single-exit point) if some of the instructions have variable latencies. This is because the worst case execution time of a basic block on out-of-order pipelines cannot be obtained by assuming maximum latencies of the individual instructions. Our timing estimation technique for a basic block is inspired by an existing performance analysis technique for tasks with data dependences and resource contentions in real-time distributed systems. We extend our analysis by modeling the interaction among consecutive basic blocks as well as the effect of instruction cache. Finally, we employ Integer Linear Programming (ILP) to compute the WCET of an entire program. The accuracy of our analysis is demonstrated via tight estimates obtained for several benchmarks.
  • No Thumbnail Available
    Item
    Performance Impact of Multithreaded Java Semantics on Multiprocessor Memory Consistency Models
    (2003-07-01T00:00:00Z) Lei XIE; Abhik ROYCHOUDHURY; Tulika MITRA
    The semantics of Java multithreading dictates all possible behaviors that a multithreaded Java program can exhibit on any platform. This is called the Java memory model and describes the allowed re-orderings among the operations in a thread. However, multiprocessor platforms traditionally have a memory consistency model of their own. Consequently memory barriers may have to be inserted to ensure that the multiprocessor execution of a multithreaded Java program respects the Java Memory Model. In this paper, we study the impact of these additional memory barriers on multiprocessor performance. We also study how different choices of the Java Memory Model a_ect multiprocessor performance. Our experimental results are obtained by simulating multithreaded Java Grande benchmarks under various software and hardware memory models.