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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 00:47:55 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-19 00:47:55 +0000 |
commit | 26a029d407be480d791972afb5975cf62c9360a6 (patch) | |
tree | f435a8308119effd964b339f76abb83a57c29483 /docs/performance/dtrace.md | |
parent | Initial commit. (diff) | |
download | firefox-26a029d407be480d791972afb5975cf62c9360a6.tar.xz firefox-26a029d407be480d791972afb5975cf62c9360a6.zip |
Adding upstream version 124.0.1.upstream/124.0.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | docs/performance/dtrace.md | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/docs/performance/dtrace.md b/docs/performance/dtrace.md new file mode 100644 index 0000000000..68e5114297 --- /dev/null +++ b/docs/performance/dtrace.md @@ -0,0 +1,49 @@ +# dtrace + +`dtrace` is a powerful Mac OS X kernel instrumentation system that can +be used to profile wakeups. This article provides a light introduction +to it. + +::: +**Note**: The [power profiling overview](power_profiling_overview.md) is +worth reading at this point if you haven't already. It may make parts +of this document easier to understand. +::: + +## Invocation + +`dtrace` must be invoked as the super-user. A good starting command for +profiling wakeups is the following. + +``` +sudo dtrace -n 'mach_kernel::wakeup { @[ustack()] = count(); }' -p $FIREFOX_PID > $OUTPUT_FILE +``` + +Let's break that down further. + +- The` -n` option combined with the `mach_kernel::wakeup` selects a + *probe point*. `mach_kernel` is the *module name* and `wakeup` is + the *probe name*. You can see a complete list of probes by running + `sudo dtrace -l`. +- The code between the braces is run when the probe point is hit. The + above code counts unique stack traces when wakeups occur; `ustack` + is short for \"user stack\", i.e. the stack of the userspace program + executing. + +Run that command for a few seconds and then hit [Ctrl]{.kbd} + [C]{.kbd} +to interrupt it. `dtrace` will then print to the output file a number of +stack traces, along with a wakeup count for each one. The ordering of +the stack traces can be non-obvious, so look at them carefully. + +Sometimes the stack trace has less information than one would like. +It's unclear how to improve upon this. + +## See also + +dtrace is *very* powerful, and you can learn more about it by consulting +the following resources: + +- [The DTrace one-liner + tutorial](https://wiki.freebsd.org/DTrace/Tutorial) from FreeBSD. +- [DTrace tools](http://www.brendangregg.com/dtrace.html), by Brendan + Gregg. |