Re: [PATCH v2 1/3] ftrace: add tracepoint for timer

Frederic Weisbecker
2009-07-07T17:40:06Z

On Tue, Jul 07, 2009 at 05:28:18PM +0800, Xiao Guangrong wrote:
>
>
> Thomas Gleixner wrote:
> > On Mon, 6 Jul 2009, Xiao Guangrong wrote:
> >> Changelog v1->v2:
> >> 1: Add jiffies info into timer
> >> 2: Combine debugobjects and trace as Thomas's suggestion
> >
> > I like it that way. Some minor nitpicks below.
> >
> >> +TRACE_EVENT(timer_expire,
> >> +
> >> + TP_PROTO(struct timer_list *timer),
> >> +
> >> + TP_ARGS(timer),
> >> +
> >> + TP_STRUCT__entry(
> >> + __field( void *, timer )
> >> + __field( void *, function )
> >
> > Do we really need the function here? It does not change between
> > start and expiry.
> >
>
> Yeah, I'll fix.
>
> >> +TRACE_EVENT(timer_cancel,
> >> +
> >> + TP_PROTO(struct timer_list *timer),
> >> +
> >> + TP_ARGS(timer),
> >> +
> >> + TP_STRUCT__entry(
> >> + __field( void *, timer )
> >> + __field( void *, function )
> >
> > Ditto.
> >
>
> Will fix.
>
> >> +
> >> +static inline void debug_and_trace_timer_expire(struct timer_list *timer)
> >
> > Technically not really necessary. The debug code does not care about
> > it.
> >
>
> Will fix.
>
> >> timer = list_first_entry(head, struct timer_list,entry);
> >> + debug_and_trace_timer_expire(timer);
> >> fn = timer->function;
> >> data = timer->data;
> >>
> >
> > Can you please add the tracepoint which was suggested by Anton (IIRC)
> > which allows us to measure the execution time of the callback function
> > ? There is no need to dereference timer in the expiry tracepoint, we
> > just store the pointer. So we can safely move the tracepoints just
> > around the function call.
> >
> > trace_timer_expire(timer);
> > fn(data);
> > trace_timer_callback_done(timer);
> >
> > Or whatever fancy name you come up with.
> >
>
> OK, I'll fix it base on your suggestion.
>
> trace_timer_expire/trace_timer_callback_done are already in Frederic' tree
> but with different name, see below URL:
> http://marc.info/?l=linux-kernel&m=124331396919301&w=2
>
> I'll modify those tracepoint's name to match ours.
>
> Thank you very much!
>
> Xiao

If you wish so, I can gather your patches with the one of Anton Blanchard
and send a pull request once it's acked.

Thanks,
Frederic.