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| author | Steven Rostedt <rostedt@goodmis.org> | 2025-05-08 09:56:39 -0400 |
|---|---|---|
| committer | Steven Rostedt (Google) <rostedt@goodmis.org> | 2025-05-09 15:19:11 -0400 |
| commit | 7b382efd5e8af4c0c67e70ad3fb599dcd2dc0b86 (patch) | |
| tree | aeaffefb516cc9edc88275c4a19a524cead16334 /Documentation/trace | |
| parent | tracing: Add a helper function to handle the dereference arg in verifier (diff) | |
| download | linux-7b382efd5e8af4c0c67e70ad3fb599dcd2dc0b86.tar.gz linux-7b382efd5e8af4c0c67e70ad3fb599dcd2dc0b86.zip | |
tracing: Allow the top level trace_marker to write into another instances
There are applications that have it hard coded to write into the top level
trace_marker instance (/sys/kernel/tracing/trace_marker). This can be
annoying if a profiler is using that instance for other work, or if it
needs all writes to go into a new instance.
A new option is created called "copy_trace_marker". By default, the top
level has this set, as that is the default buffer that writing into the
top level trace_marker file will go to. But now if an instance is created
and sets this option, all writes into the top level trace_marker will also
be written into that instance buffer just as if an application were to
write into the instance's trace_marker file.
If the top level instance disables this option, then writes to its own
trace_marker and trace_marker_raw files will not go into its buffer.
If no instance has this option set, then the write will return an error
and errno will contain ENODEV.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250508095639.39f84eda@gandalf.local.home
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Diffstat (limited to 'Documentation/trace')
| -rw-r--r-- | Documentation/trace/ftrace.rst | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index c9e88bf65709..af66a05e18cc 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -1205,6 +1205,19 @@ Here are the available options: default instance. The only way the top level instance has this flag cleared, is by it being set in another instance. + copy_trace_marker + If there are applications that hard code writing into the top level + trace_marker file (/sys/kernel/tracing/trace_marker or trace_marker_raw), + and the tooling would like it to go into an instance, this option can + be used. Create an instance and set this option, and then all writes + into the top level trace_marker file will also be redirected into this + instance. + + Note, by default this option is set for the top level instance. If it + is disabled, then writes to the trace_marker or trace_marker_raw files + will not be written into the top level file. If no instance has this + option set, then a write will error with the errno of ENODEV. + annotate It is sometimes confusing when the CPU buffers are full and one CPU buffer had a lot of events recently, thus |