Load Trace Playback

Load trace playback means generating work (via dummy loops executed by a gang of processes) on the playback machine that reflects the load average values provided in a load trace from some other machine. As a side effect, the load average on the playback machine will approximate the load average samples in the trace. If the machine has no other load, then the load average will approximately track the trace's load average.

Load trace playback and the playload tool you can download below are fully described in the following paper:

  • P. Dinda, D. O'Hallaron, Realistic CPU Workloads Through Host Load Trace Playback, In Proc. 5th Workshop on Languages, Compilers, and Run-time Systems for Scalable Computers, Rochester, NT, May, 2000. abstract postscript

  • Playload: A Load Trace Playback Tool

    Playload implements load trace playback on Unix systems. The only requirement is that you have a C compiler. We have tested it on Digital Unix, Linux, Solaris, and FreeBSD systems. The playload README provides a detailed description of the tool and the issues involved in load trace playback. You can also download playload (25K). If you're looking for load traces, you can check out our 800 MB load trace archive.

    Example of Load Trace Playback

    We played this load trace (439K), on a four different machines using playload's "work-based" policy. The trace was collected from an interactive Digital Unix machine in the PSC's Alpha cluster on August 23, 1997. You can learn more about the trace in this tech report. The following graphs show the first hour of these playbacks. The green curves show the original load trace. The blue curves show what ideal playback would look like on the different machines given their different amounts of smoothing, and delay during playback. The Digital Unix machine uses a 5 second exponential average, while the others use a 60 second exponential average. The red curves show the actual measured load average over time.

    Digital Unix




    Peter Dinda
    Last modified: Mon Feb 12 10:14:47 CST 2001