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Instrumentation and Profiling

Instrumentation and Profiling. David Kaeli Department of Electrical and Computer Engineering Northeastern University Boston, MA kaeli@ece.neu.edu. Application Areas. Trace generation Performance profiling Dynamic optimization Binary translation Power/energy management

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Instrumentation and Profiling

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  1. Instrumentation and Profiling David Kaeli Department of Electrical and Computer Engineering Northeastern University Boston, MA kaeli@ece.neu.edu

  2. Application Areas • Trace generation • Performance profiling • Dynamic optimization • Binary translation • Power/energy management • Architecture/hardware design studies • Virtualization • Software validation and testing • Information security

  3. Definitions • Instrumentation – A hardware or software probe that provides access to either machine state or program state • Profiling – The ability to capture information available through instrumentation • Tracing – One form of profiling that captures execution information in the form of a sequential record • Static – Techniques applied before a program runs (i.e., at compile time) • Dynamic – Techniques applied as the program executes (i.e., at run time)

  4. Definitions • Trace-driven simulation • Using a previously collected trace as input to a simulator • Execution-driven simulation • Tracing and simulating concurrently • Tracing Level - • Source – high-level language program • Object – unlinked binary file • Executable – linked, runable, binary file

  5. Definitions • Binary translation – translating between two binary executable formats • Binary optimization – modifying the binary to produce an optimized binary • Emulation - One software program, executing software binary, potentially targeting a different ISA

  6. Why are Instrumentation and Profiling important topics? • Allow for pre-hardware evaluation • Enable performance tuning after the hardware has been delivered • Enable software to adapt to changes in workload usage • Provide quantitative software testing quality • Provide for power estimation • Enable increased security • Enable next-generation hardware design criteria

  7. History of Instrumentation • IBM Mainframe Instrumentation Systems (1981) • Instrumentation implemented in customized hardware (Logic Support Subsystem) • Provides performance data directly to the customer • Allowed for load balancing and capacity planning • Also provided a level of online diagnostic system • Hang detection • Recovery • Intel In-Circuit-Emulators • Started with Intel 80386 in mid-80’s • Externalized signals to ICE pins • Allowed for external control of hardware functions (e.g., L1 caching) • Hardware Counters • VAX 8800, Pentiums, PowerPCs, SPARCs, Alphas • On most CPUs today

  8. History of Instrumentation SDS Sigma 7 UCLA 1967

  9. History of Profiling • Hardware tracing • Early memory studies (Belady, Denning) • VAX-Tracer (Emer and Clark ISCA 1984) • LLATT (IBM 1985) • ATUM (Stanford, Anant Agarwal 1989) • TRAPEDS (Stunkel, Univ. of Illinois 1989) • Trace/Trap (IBM - Sigmetrics 1989) • Logic Analyzers • Used to debug early hardware • Used to tune programs (very difficult to do) • Used to obtain traces for architectural studies • Counter readers • VAX8800 Histogram Monitors • DCPI – Digital Equipment (Alpha)

  10. History of Profiling 1979 – Hewlett Packard Model 85 Used for control and data acquisition

  11. Issues with Instrumentation and Profiling • Overhead – what type of perturbation does the instrumentation and profiling introduce? • Accuracy – does our profile reflect the actual execution? • Completeness – do I capture OS, interrupts, libraries?? • Portability – is my approach ISA and OS independent? • Input independence – does my output change for different inputs? • Capacity – how much can I capture? • Speed – do I catch the fastest event of interest? • Cost – is this worth the investment?

  12. Today, Profiling, Simulation and Tracing have become mainstream research areas • Cost of simulation is too high • Need for increased performance accuracy • Need for software security • Need to model increasingly complex designs • New workshops and symposia: • IEEE International Symposium on Workload Characterization – annual conference • Workshop on Binary Instrumentation and Analysis (held with PACT in 2005 and 2006, special issue of Dec 2005 ACM SIGARCH News) • ACM Symposium on Code Generation and Optimization (feedback directed optimization) – annual conference • ACM Transactions on Architecture and Code Optimization – high quality ACM journal

  13. This class will: • Present a range of technologies that fall under the broad definition of profiling and instrumentation • Present some recent implementations that utilize these technologies to improve performance, scalability, reliability, power and security • Involve readings from the literature and a lab assignment

  14. Your grade in this class will be based on: • Your course project – 40% • Your paper review – 40% • Your participation in class – 20% • Questions and discussion are encouraged!

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