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Message-Id: <1415123165-3020-1-git-send-email-peter@hurleysoftware.com> Date: Tue, 4 Nov 2014 12:46:05 -0500 From: Peter Hurley <peter@...leysoftware.com> To: Steven Rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...hat.com> Cc: linux-kernel@...r.kernel.org, Peter Hurley <peter@...leysoftware.com> Subject: [PATCH v2] ftrace: Document filter and option limitations When using the function or function_graph tracers from the command line, certain command line options have limitations. Document that only kernel built-in functions can be filtered via ftrace_filter= or ftrace_graph_filter=. Document that tracer-specific options cannot be set on the command line via trace_options. Document that ftrace cannot do late binding for function filters. Signed-off-by: Peter Hurley <peter@...leysoftware.com> --- Documentation/kernel-parameters.txt | 6 ++++++ Documentation/trace/ftrace.txt | 7 +++++-- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 4c81a86..d098ead 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1121,6 +1121,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted. list of functions. This list can be changed at run time by the set_ftrace_filter file in the debugfs tracing directory. + Only kernel built-in functions can be filtered. ftrace_notrace=[function-list] [FTRACE] Do not trace the functions specified in @@ -1134,6 +1135,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted. function-list is a comma separated list of functions that can be changed at run time by the set_graph_function file in the debugfs tracing directory. + Only kernel built-in functions can be filtered. ftrace_graph_notrace=[function-list] [FTRACE] Do not trace from the functions specified in @@ -3521,6 +3523,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted. trace_options=stacktrace + Tracer-specific options are ignored when set this way. + For example, the 'func_stack_trace' option cannot be + set here. + See also Documentation/trace/ftrace.txt "trace options" section. diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt index 4da4261..d540273 100644 --- a/Documentation/trace/ftrace.txt +++ b/Documentation/trace/ftrace.txt @@ -188,7 +188,8 @@ of ftrace. Here is a list of some of the key files: in with practically no overhead in performance. This also 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. + will limit the trace to only those functions. Only already- + loaded functions can be filtered. This interface also allows for commands to be used. See the "Filter commands" section for more details. @@ -208,7 +209,9 @@ of ftrace. Here is a list of some of the key files: Set a "trigger" function where tracing should start with the function graph tracer (See the section - "dynamic ftrace" for more details). + "dynamic ftrace" for more details). As with set_ftrace_filter, + only names of already-loaded functions can be written to + this file. available_filter_functions: -- 2.1.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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