tracing: Add documentation for trace commands mod, traceon/traceoff
The mod command went in as commit64e7c44061
The traceon/traceoff commands went in as commit23b4ff3aa4
Signed-off-by: Chase Douglas <chase.douglas@canonical.com> LKML-Reference: <1272045759-32018-1-git-send-email-chase.douglas@canonical.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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@ -155,6 +155,9 @@ of ftrace. Here is a list of some of the key files:
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to be traced. Echoing names of functions into this file
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to be traced. Echoing names of functions into this file
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will limit the trace to only those functions.
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will limit the trace to only those functions.
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This interface also allows for commands to be used. See the
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"Filter commands" section for more details.
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set_ftrace_notrace:
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set_ftrace_notrace:
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This has an effect opposite to that of
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This has an effect opposite to that of
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@ -1824,6 +1827,47 @@ this special filter via:
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echo > set_graph_function
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echo > set_graph_function
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Filter commands
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---------------
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A few commands are supported by the set_ftrace_filter interface.
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Trace commands have the following format:
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<function>:<command>:<parameter>
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The following commands are supported:
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- mod
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This command enables function filtering per module. The
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parameter defines the module. For example, if only the write*
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functions in the ext3 module are desired, run:
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echo 'write*:mod:ext3' > set_ftrace_filter
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This command interacts with the filter in the same way as
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filtering based on function names. Thus, adding more functions
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in a different module is accomplished by appending (>>) to the
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filter file. Remove specific module functions by prepending
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'!':
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echo '!writeback*:mod:ext3' >> set_ftrace_filter
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- traceon/traceoff
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These commands turn tracing on and off when the specified
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functions are hit. The parameter determines how many times the
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tracing system is turned on and off. If unspecified, there is
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no limit. For example, to disable tracing when a schedule bug
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is hit the first 5 times, run:
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echo '__schedule_bug:traceoff:5' > set_ftrace_filter
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These commands are cumulative whether or not they are appended
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to set_ftrace_filter. To remove a command, prepend it by '!'
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and drop the parameter:
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echo '!__schedule_bug:traceoff' > set_ftrace_filter
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trace_pipe
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trace_pipe
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----------
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----------
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