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SubjectRe: [PATCH 0/2] ftrace: updates to tip

* Steven Rostedt <rostedt@goodmis.org> wrote:

> Ingo,
>
> The first patch is critical, and needs to stay with trace_output.c Not
> that critical since trace_output.c is not in mainline yet.
>
> The second patch gives the ability to stack trace functions. I've been
> leery about adding this and still keep it a separate option from the
> "stacktrace" that already exists. This is because when enabled with no
> filtering, the lag between typing and seeing what is typed can be up to
> 10 seconds or more.

Btw., is this true even if frame pointers are enabled? When frame pointers
are disabled we scan the full kernel stack => that can be quite slow if
every kernel function is traced ;-)

> I made the function stack trace an option attached to the function
> tracer, so it must be enabled after the function tracer has been set.
> This still needs to be updated in ftrace.txt.

maybe we could drive this via the filter API? Something like:

echo "*btrfs*:stacktrace" >> set_filter_functions

Would automatically mean that those functions will all generate
stacktraces too. Note how safe this API is by default: the filter is used
for a narrow scope of functions anwyay. To get it for all kernel functions
one would have to do:

echo "*:stacktrace" >> set_filter_functions

Which one cannot do accidentally.

What do you think?

> The following patches are in:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
>
> branch: tip/devel
>
>
> Lai Jiangshan (1):
> ftrace: fix trace_output
>
> Steven Rostedt (1):
> ftrace: add stack trace to function tracer
>
> ----
> kernel/trace/trace.c | 26 ++++++++----
> kernel/trace/trace.h | 7 +++
> kernel/trace/trace_functions.c | 84 ++++++++++++++++++++++++++++++++++++++++
> kernel/trace/trace_output.c | 65 +++++++++++++++----------------
> kernel/trace/trace_output.h | 4 +-
> 5 files changed, 141 insertions(+), 45 deletions(-)

Pulled into tip/tracing/ftrace, thanks Steve!

Ingo


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