Re: [PATCH] tracing/ftrace: add an option to not print the contextinfo for events

From: Frederic Weisbecker
Date: Sun Jan 25 2009 - 11:25:17 EST


On Tue, Jan 20, 2009 at 09:55:17PM -0500, Steven Rostedt wrote:
>
> On Tue, 20 Jan 2009, Frederic Weisbecker wrote:
>
> > Impact: make trace_event more convenient for tracers
> >
> > All tracers (for the moment) that use the struct trace_event want to have
> > the context info printed before their own output: the pid/cmdline, cpu, and timestamp.
> >
> > But some other tracers that want to implement their trace_event callbacks will
> > not necessary need these information.
> >
> > This patch adds a new default-enabled trace option: TRACE_ITER_CONTEXT_INFO
> > When disabled through:
> >
> > echo nocontext-info > /debugfs/tracing/trace_options
>
> Thanks Frederic,
>
> >
> > The pid, cpu and timestamps headers will not be printed.
> >
> > IE with the sched_switch tracer with context-info (default):
> >
> > bash-2935 [001] 100.356561: 2935:120:S ==> [001] 0:140:R <idle>
> > <idle>-0 [000] 100.412804: 0:140:R + [000] 11:115:S events/0
> > <idle>-0 [000] 100.412816: 0:140:R ==> [000] 11:115:R events/0
> > events/0-11 [000] 100.412829: 11:115:S ==> [000] 0:140:R <idle>
> >
> > Without context-info:
> >
> > 2935:120:S ==> [001] 0:140:R <idle>
> > 0:140:R + [000] 11:115:S events/0
> > 0:140:R ==> [000] 11:115:R events/0
> > 11:115:S ==> [000] 0:140:R <idle>
> >
> > A tracer can disable it at runtime by clearing the bit TRACE_ITER_CONTEXT_INFO in trace_flags.
>
> How about adding another function method into the tracer, where it could
> be what is printed at the start. The default being what is now printed.
> This would be for trace and latency trace only.
>
>
> >
> > Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> > ---
> > kernel/trace/trace.c | 61 ++++++++++++++++++++++++++++---------------------
> > kernel/trace/trace.h | 3 +-
> > 2 files changed, 37 insertions(+), 27 deletions(-)
> >
> > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> > index 220c264..a59ba48 100644
> > --- a/kernel/trace/trace.c
> > +++ b/kernel/trace/trace.c
> > @@ -227,7 +227,7 @@ static DECLARE_WAIT_QUEUE_HEAD(trace_wait);
> >
> > /* trace_flags holds trace_options default values */
> > unsigned long trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_PRINTK |
> > - TRACE_ITER_ANNOTATE;
> > + TRACE_ITER_ANNOTATE | TRACE_ITER_CONTEXT_INFO;
> >
> > /**
> > * trace_wake_up - wake up tasks waiting for trace input
> > @@ -285,6 +285,7 @@ static const char *trace_options[] = {
> > "userstacktrace",
> > "sym-userobj",
> > "printk-msg-only",
> > + "context-info",
> > NULL
> > };
> >
> > @@ -1487,21 +1488,23 @@ static enum print_line_t print_trace_fmt(struct trace_iterator *iter)
> >
> > test_cpu_buff_start(iter);
> >
> > - comm = trace_find_cmdline(iter->ent->pid);
> > -
> > - t = ns2usecs(iter->ts);
> > - usec_rem = do_div(t, 1000000ULL);
> > - secs = (unsigned long)t;
> > -
> > - ret = trace_seq_printf(s, "%16s-%-5d ", comm, entry->pid);
> > - if (!ret)
> > - return TRACE_TYPE_PARTIAL_LINE;
> > - ret = trace_seq_printf(s, "[%03d] ", iter->cpu);
> > - if (!ret)
> > - return TRACE_TYPE_PARTIAL_LINE;
> > - ret = trace_seq_printf(s, "%5lu.%06lu: ", secs, usec_rem);
> > - if (!ret)
> > - return TRACE_TYPE_PARTIAL_LINE;
> > + if (trace_flags & TRACE_ITER_CONTEXT_INFO) {
> > + comm = trace_find_cmdline(iter->ent->pid);
> > +
> > + t = ns2usecs(iter->ts);
> > + usec_rem = do_div(t, 1000000ULL);
> > + secs = (unsigned long)t;
> > +
> > + ret = trace_seq_printf(s, "%16s-%-5d ", comm, entry->pid);
> > + if (!ret)
> > + return TRACE_TYPE_PARTIAL_LINE;
> > + ret = trace_seq_printf(s, "[%03d] ", iter->cpu);
> > + if (!ret)
> > + return TRACE_TYPE_PARTIAL_LINE;
> > + ret = trace_seq_printf(s, "%5lu.%06lu: ", secs, usec_rem);
> > + if (!ret)
> > + return TRACE_TYPE_PARTIAL_LINE;
> > + }
>
> Or here we can do a:
>
> if (iter->tr->context_info)
> ret = iter->tr->context_info(s, iter);
> else
> ret = default_context_info(s, iter);
>
> This may give a tracer more control as to what to print for each entry.
>
> -- Steve
>


So what do you suggest actually? To keep TRACE_ITER_CONTEXT_INFO and add
two callbacks to control trace and latency_trace?

Or completely drop the option and only add these callbacks?

Keeping both will let a tracer decide if it wants to keep the headers for binary, hex
and raw too..

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/