Re: [Patch 2/2] tracepoints for softirq entry/exit - tracepoints

Ingo Molnar
2009-03-12T23:49:57Z

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> On Thu, Mar 12, 2009 at 02:36:03PM -0400, Jason Baron wrote:
> >
> > introduce softirq entry/exit tracepoints. These are useful for
> > augmenting existing tracers, and to figure out softirq frequencies and
> > timings.
> >
> > Signed-off-by: Jason Baron <jbaron@redhat.com>
> >
> > ---
> >
> > include/trace/irq_event_types.h | 12 ++++++++++++
> > kernel/softirq.c | 7 ++++++-
> > 2 files changed, 18 insertions(+), 1 deletions(-)
> >
> >
> > diff --git a/include/trace/irq_event_types.h b/include/trace/irq_event_types.h
> > index 214bb92..38b4bdd 100644
> > --- a/include/trace/irq_event_types.h
> > +++ b/include/trace/irq_event_types.h
> > @@ -40,4 +40,16 @@ TRACE_EVENT(irq_handler_exit,
> > __entry->irq, __entry->ret ? "handled" : "unhandled")
> > );
> >
> > +TRACE_FORMAT(irq_softirq_entry,
> > + TP_PROTO(struct softirq_action *h, struct softirq_action *vec),
> > + TP_ARGS(h, vec),
> > + TP_FMT("softirq=%d action=%s", h - vec, softirq_to_name[h-vec])
> > + );
> > +
> > +TRACE_FORMAT(irq_softirq_exit,
> > + TP_PROTO(struct softirq_action *h, struct softirq_action *vec),
> > + TP_ARGS(h, vec),
> > + TP_FMT("softirq=%d action=%s", h - vec, softirq_to_name[h-vec])
> > + );
> > +
> > #undef TRACE_SYSTEM
> > diff --git a/kernel/softirq.c b/kernel/softirq.c
> > index ba1511f..c378d53 100644
> > --- a/kernel/softirq.c
> > +++ b/kernel/softirq.c
> > @@ -24,6 +24,7 @@
> > #include <linux/ftrace.h>
> > #include <linux/smp.h>
> > #include <linux/tick.h>
> > +#include <trace/irq.h>
> >
> > #include <asm/irq.h>
> > /*
> > @@ -186,6 +187,9 @@ EXPORT_SYMBOL(local_bh_enable_ip);
> > */
> > #define MAX_SOFTIRQ_RESTART 10
> >
> > +DEFINE_TRACE(irq_softirq_entry);
> > +DEFINE_TRACE(irq_softirq_exit);
>
>
> Just one nit here. The "irq_" prefix seems to me too much.
> On the trace we have:
>
> /* irq_softirq_entry: softirq=nb action=nb_to_logical_name */
>
> It's even too much words that says the same things.
> Moreover, we have the logical name, the number seems not very useful
> because we have its logical translation just after.
>
> I would suggest to have just:
>
> /* softirq_entry: nb_to_logical_name */
>
> ie:
>
> /* softirq_entry: SCHED_SOFTIRQ */
>
> Don't you think it's more clear and obvious?

yeah.

> Other than that, I think these tracepoints are a good idea.

agreed.

Acked-by: Ingo Molnar <mingo@elte.hu>

Ingo