linux-kernel - Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle period

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Date:	Thu, 21 Jan 2016 15:12:07 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
cc:	peterz@...radead.org, rafael@...nel.org, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, nicolas.pitre@...aro.org,
	vincent.guittot@...aro.org
Subject: Re: [RFC V2 2/2] sched: idle: IRQ based next prediction for idle
 period

On Thu, 21 Jan 2016, Daniel Lezcano wrote:
> On 01/20/2016 08:49 PM, Thomas Gleixner wrote:
> > So now for the allocation/free of that data. We simply allocate/free it
> > along
> > with the irq descriptor. That IRQS_TIMING bit gets set in __setup_irq()
> > except
> > for timer interrupts. That's simple and avoid _all_ the issues.
> 
> Indeed, making this as part of the irq code makes everything much more simple
> and self contained. For the shared interrupts, shouldn't we put the timings
> samples into the irqaction structure instead of the irqdesc structure ?
> 
> eg.
> 
> #define IRQT_MAX_VALUES 4
> 
> struct irqaction {
> 	...
> #ifdef CONFIG_IRQ_TIMINGS
> 	u32 irqtimings_samples[IRQT_MAX_VALUES];
> #endif
> 	...
> };
> 
> So we don't have to deal with the allocation/free under locks. The drawback is
> the array won't be used in the case of the timers.

I still have to ask the question whether a per device information is useful at
all. I don't see the value, but I might miss something.

Thanks,

	tglx