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SubjectRe: [RFC][PATCH] tracing: Make branch trace display correct header
On Mon, Apr 13, 2009 at 04:02:34PM +0800, Zhaolei wrote:
> Before patch:
> # tracer: branch
> #
> # TASK-PID CPU# TIMESTAMP FUNCTION
> # | | | | |
> <...>-2981 [000] 24008.872738: [ ok ] trace_irq_handler_exit:irq_event_types.h:41
> <...>-2981 [000] 24008.872742: [ ok ] note_interrupt:spurious.c:229
> ...
>
> After patch:
> # tracer: branch
> #
> # TASK-PID CPU# TIMESTAMP CORRECT FUNC:FILE:LINE
> # | | | | | |
> <...>-2985 [000] 26329.142970: [ ok ] slab_free:slub.c:1776
> <...>-2985 [000] 26329.142972: [ ok ] trace_kmem_cache_free:kmem_event_types.h:191
> ...
>
> But it is not the best fix way.
> When format(length) of TASK-PID, CPU and TIMESTAMP chanegd in trace.c,
> other files who uses there fields need to changed for print right header line.
>
> Maybe we can make a function to print header line of these 3 field:
> print_common_head()
> {
> seq_puts(s, "# TASK-PID CPU# TIMESTAMP");
> }
>
> and call this function in other files' print_header:
> static void branch_print_header(struct seq_file *s)
> {
> print_common_head();
> seq_puts(s, " CORRECT FUNC:FILE:LINE\n");
> }
>
> But if header line is multi-line, this way can't work.
>
> Another way is to export specific header-line content in other files:
> static void branch_print_header(char *buf, int len)
> {
> strcpy(buf, " CORRECT FUNC:FILE:LINE\n"
> " | |\n"
> );
> }
> And combile common-header and specific header in trace.c, then do seq_puts.
> But this seems too complex for tracing framework.
>
> Similar problem exists in other tracers as sched_switch.


Indeed. I don't see any smart solution.
May be:

print_common_header_begin() // first line
print_common_header_end() // second line with pipes
That's not pretty but at least it factorizes...

Hm?

Frederic.



> Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
> ---
> kernel/trace/trace_branch.c | 8 ++++++++
> 1 files changed, 8 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
> index 8e64e60..7a7a9fd 100644
> --- a/kernel/trace/trace_branch.c
> +++ b/kernel/trace/trace_branch.c
> @@ -157,6 +157,13 @@ static enum print_line_t trace_branch_print(struct trace_iterator *iter,
> return TRACE_TYPE_HANDLED;
> }
>
> +static void branch_print_header(struct seq_file *s)
> +{
> + seq_puts(s, "# TASK-PID CPU# TIMESTAMP CORRECT"
> + " FUNC:FILE:LINE\n");
> + seq_puts(s, "# | | | | | "
> + " |\n");
> +}
>
> static struct trace_event trace_branch_event = {
> .type = TRACE_BRANCH,
> @@ -171,6 +178,7 @@ static struct tracer branch_trace __read_mostly =
> #ifdef CONFIG_FTRACE_SELFTEST
> .selftest = trace_selftest_startup_branch,
> #endif /* CONFIG_FTRACE_SELFTEST */
> + .print_header = branch_print_header,
> };
>
> __init static int init_branch_tracer(void)
> -- 1.5.5.3
>



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