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