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Documentation: ftrace: clarify filters with dynamic ftrace and graph 

I fell into the trap of having set up function tracer with a very
limited filter and then switched over to function_graph and was
erroneously wondering why the latter did not trace what I expected,
which was the full unabridged graph recursion.

Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Steffen Maier 2018-04-13 17:39:15 +02:00 committed by Jonathan Corbet
parent 1ba2211c52
commit 32fb7ef69a
1 changed files with 6 additions and 1 deletions
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7
Documentation/trace/ftrace.rst
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@ -224,6 +224,8 @@ of ftrace. Here is a list of some of the key files:
has a side effect of enabling or disabling specific functions
to be traced. Echoing names of functions into this file
will limit the trace to only those functions.
This influences the tracers "function" and "function_graph"
and thus also function profiling (see "function_profile_enabled").
The functions listed in "available_filter_functions" are what
can be written into this file.
@ -265,6 +267,8 @@ of ftrace. Here is a list of some of the key files:
Functions listed in this file will cause the function graph
tracer to only trace these functions and the functions that
they call. (See the section "dynamic ftrace" for more details).
Note, set_ftrace_filter and set_ftrace_notrace still affects
what functions are being traced.
set_graph_notrace:
@ -277,7 +281,8 @@ of ftrace. Here is a list of some of the key files:
This lists the functions that ftrace has processed and can trace.
These are the function names that you can pass to
"set_ftrace_filter" or "set_ftrace_notrace".
"set_ftrace_filter", "set_ftrace_notrace",
"set_graph_function", or "set_graph_notrace".
(See the section "dynamic ftrace" below for more details.)
dyn_ftrace_total_info: