Re: [RFC V2 1/2] irq: Add a framework to measure interrupt timings

[Daniel Lezcano]

On 01/20/2016 08:07 PM, Peter Zijlstra wrote:
> On Wed, Jan 20, 2016 at 05:00:32PM +0100, Daniel Lezcano wrote:
> > +++ b/kernel/irq/handle.c
> > @@ -165,6 +165,7 @@ irqreturn_t handle_irq_event_percpu(struct irq_desc *desc)
> >   			/* Fall through to add to randomness */
> >   		case IRQ_HANDLED:
> >   			flags |= action->flags;
> > +			handle_irqtiming(irq, action->dev_id);
> >   			break;
> >
> >   		default:
>
> > +++ b/kernel/irq/internals.h
>
> > +static inline void handle_irqtiming(unsigned int irq, void *dev_id)
> > +{
> > +	if (__irqtimings->handler)
> > +		__irqtimings->handler(irq, ktime_get(), dev_id);
> > +}
>
> Here too, ktime_get() is daft.
>
> Also, you really want to take the timestamp _before_ we call the
> handlers, not after, otherwise you mix in whatever variance exist in the
> handler duration.

Indeed.



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