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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Mathieu Desnoyers <compudj@krystal.dyndns.org>,
       Jason Baron <jbaron@redhat.com>
Subject: Re: [PATCH] new irq tracer
Cc: kosaki.motohiro@jp.fujitsu.com, mingo@elte.hu, rostedt@goodmis.org,
       linux-kernel@vger.kernel.org, acme@ghostprotocols.net,
       fweisbec@gmail.com, fche@redhat.com, peterz@infradead.org
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Date: Thu, 19 Feb 2009 10:42:08 +0900 (JST)
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Hi Jason,

> * Jason Baron (jbaron@redhat.com) wrote:
> > hi,
> > 
> > Using a copule of tracepoints i've implemented an 'irq tracer' which has
> > the following column format:
> > 
> > [time][irq][action][handled][cpu][length]
> > 
> > for example on my system:
> > 
> > [ 1038.927248381]     28     eth0      1        3     0.000002745
> > [ 1038.927544688]     28     eth0      1        3     0.000002520
> > [ 1038.927593609]     28     eth0      1        3     0.000002509
> > [ 1038.974087675]     29     ahci      1        1     0.000013135
> > [ 1038.974288475]     29     ahci      1        1     0.000005542
> > [ 1038.974414324]     29     ahci      1        1     0.000007953
> > 
> > I think this patch is useful in understanding irq system behavior, and
> > for tracking down irq driver handlers that are firing too often or
> > spending too much time handling an irq. This approach could be extended
> > to the timer irq and for softirqs...
> > 
> > thanks,



> > @@ -354,7 +358,9 @@ irqreturn_t handle_IRQ_event(unsigned int irq, struct irqaction *action)
> >  		local_irq_enable_in_hardirq();
> >  
> >  	do {
> > +		trace_irq_entry(irq);
> >  		ret = action->handler(irq, action->dev_id);
> > +		trace_irq_exit(irq, ret);
> >  		if (ret == IRQ_HANDLED)
> >  			status |= action->flags;
> >  		retval |= ret;

May I ask why you select this line?

IOW, I guess your probe point is interest to irq action and mathieu's 
probe point is interest to interrupt itself.

I guess you also want to observe shared irq problem, right?