realtime:documentation:howto:tools:cyclictest:tracing
Differences
This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision Next revision | Previous revision Last revision Both sides next revision | ||
|
realtime:documentation:howto:tools:cyclictest:tracing [2022/01/19 19:54] bartwensley [Break Trace Option] |
realtime:documentation:howto:tools:cyclictest:tracing [2022/01/19 20:00] bartwensley [Measuring the Tracing Overhead] Removed --ftrace option as it was removed from cyclictest in rt-tests version 1.4. |
||
|---|---|---|---|
| Line 13: | Line 13: | ||
| ===== Selecting Instrumentation ===== | ===== Selecting Instrumentation ===== | ||
| - | Cyclictest offers a number options which use different Ftrace tracers and instrumentation. These options are described in the Cyclictest help text (--help) and on the man page. The most important things to keep in mind when choosing instrumentation are the trace detail and the resulting overhead. A trace with more detail will require a higher overhead. In general, it is effective to corner the source of the latency over several iterations of tracing and analysis while gradually increasing the trace detail. Start with a small amount of instrumentation, which produces a simple trace. One good option would be to start by eliminating the most obvious possible sources of latency by tracing when interrupts or preemption are disabled. | + | Ftrace provides a selection of tracers and instrumentation. These options are described in the Ftrace documentation [[realtime:documentation:howto:tools:ftrace|here]]. The most important things to keep in mind when choosing instrumentation are the trace detail and the resulting overhead. A trace with more detail will require a higher overhead. In general, it is effective to corner the source of the latency over several iterations of tracing and analysis while gradually increasing the trace detail. Start with a small amount of instrumentation, which produces a simple trace. One good option would be to start by eliminating the most obvious possible sources of latency by tracing when interrupts or preemption are disabled. |
| ==== Function Tracing ==== | ==== Function Tracing ==== | ||
| Line 39: | Line 39: | ||
| </code> | </code> | ||
| - | and after a couple hours a maximum latency of 130 us is detected. To measure the value of the maximum latency with the overhead from function tracing, the following Cyclictest command could be run: | + | and after a couple hours a maximum latency of 130 us is detected. To measure the value of the maximum latency with the overhead from function tracing, ftrace can be enabled and then the following Cyclictest command could be run: |
| <code bash> | <code bash> | ||
| - | cyclictest --mlockall --smp --priority=80 --interval=200 --distance=0 --breaktrace=2000 --ftrace | + | cyclictest --mlockall --smp --priority=80 --interval=200 --distance=0 --breaktrace=2000 --tracemark |
| </code> | </code> | ||
realtime/documentation/howto/tools/cyclictest/tracing.txt ยท Last modified: 2022/01/19 20:01 by bartwensley
Page Tools
Except where otherwise noted, content on this wiki is licensed under the following license: CC Attribution-Noncommercial-Share Alike 4.0 International
