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

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Date:	Fri, 13 Mar 2009 00:49:12 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Jason Baron <jbaron@...hat.com>, rostedt@...dmis.org,
	linux-kernel@...r.kernel.org, acme@...stprotocols.net,
	fche@...hat.com, peterz@...radead.org, compudj@...stal.dyndns.org
Subject: Re: [Patch 2/2] tracepoints for softirq entry/exit - tracepoints


* Frederic Weisbecker <fweisbec@...il.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@...hat.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@...e.hu>

	Ingo
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