Re: [PATCH 00/15] [git pull] for tip/tracing/ftrace

Steven Rostedt
2009-02-17T12:49:59Z

On Tue, 17 Feb 2009, Ingo Molnar wrote:

>
> * Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > Ingo,
> >
> > This is a patch series that offers a variety of features.
> >
> > The first is to add:
> >
> > #### all functions enabled ####
> >
> > to set_ftrace_filter when all functions will be traced when function
> > tracing is on.
> >
> > The next is to add a :command: interface, and the module command:
> >
> > echo '*:mod:ext4' > set_ftrace_filter
> >
> > Will select all functions in the ext4 module.
> >
> > echo '!*write*:mod:ext4' > set_ftrace_filter
> >
> > will remove all functions with the characters 'write' and are
> > in ext4.
>
> Very nice feature!
>
> I'm wondering, would it be possible to somehow extend this to
> built-in drivers too, so that we get symmetry of usage
> independently of whether something is built in or a module? I
> suspect it needs some extensions to kbuild though ...

Yeah, that may needs some kbuild magic.

>
> > Next we extend the :command: interface as well as add a way to
> > hook tracers to specific functions. Instead of tracing all functions
> > the same, this patch series adds a hash to be able to trace different
> > functions differently.
>
> That's a nice extension too!
>
> Small naming detail: instead of calling it a 'hook' (which
> really has a bad sound to it for various reasons), how about
> calling it a 'trigger' and/or a 'callback'?

Hmm, I can switch it to trigger. I used callback in too many other
places in this series, and that would lead to more confusion.

>
> > I implement a 'traceon' and 'traceoff' to have a function
> > start or stop tracing when it is hit. It also includes a
> > counter for the number of times to implement the trace on/off.
> >
> > echo '*_lock:traceon:4' > set_ftrace_filter
> > echo '*_unlock:traceoff:5' > set_ftrace_filter
>
> if there's no counter specified, does it default to 1
> [single-shot trigger] or infinity?

Bad documentation on my part :-/

No number is infinity, since infinity is no number ;-)

>
> > This will have all functions that end with _lock turn on
> > tracing and all that end with _unlock disable it, 4 times
> > each.
> >
> > The following patches are in:
> >
> > git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
> >
> > branch: tip/tracing/ftrace
> >
> >
> > Steven Rostedt (15):
> > ftrace: state that all functions are enabled in set_ftrace_filter
> > ftrace: add do_for_each_ftrace_rec and while_for_each_ftrace_rec
> > ftrace: rename ftrace_match to ftrace_match_records
> > ftrace: break up ftrace_match_records into smaller components
> > ftrace: add module command function filter selection
> > ftrace: enable filtering only when a function is filtered on
> > ftrace: add command interface for function selection
> > ftrace: convert ftrace_lock from a spinlock to mutex
> > ftrace: consolidate mutexes
> > ftrace: trace different functions with a different tracer
> > ring-buffer: add tracing_is_on to test if ring buffer is enabled
> > ftrace: add traceon traceoff commands to enable/disable the buffers
> > ftrace: show selected functions in set_ftrace_filter
> > ftrace: add pretty print to selected fuction traces
> > ftrace: add pretty print function for traceon and traceoff hooks
> >
> > ----
> > include/linux/ftrace.h | 40 ++
> > include/linux/ring_buffer.h | 2 +
> > kernel/trace/ftrace.c | 929 +++++++++++++++++++++++++++++++---------
> > kernel/trace/ring_buffer.c | 9 +
> > kernel/trace/trace_functions.c | 163 +++++++
> > 5 files changed, 946 insertions(+), 197 deletions(-)
>
> Pulled into tip:tracing/ftrace, thanks Steve!

Thanks! This answers my other question. I'll be sending out clean up
patches later today.

-- Steve