linux-kernel - Re: [PATCH V6] irq: Track the interrupt timings

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Message-ID: <alpine.LFD.2.20.1606141636510.1714@knanqh.ubzr>
Date:	Tue, 14 Jun 2016 16:38:06 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
cc:	tglx@...utronix.de, shreyas@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, peterz@...radead.org,
	rafael@...nel.org, vincent.guittot@...aro.org
Subject: Re: [PATCH V6] irq: Track the interrupt timings

On Tue, 14 Jun 2016, Daniel Lezcano wrote:

> The interrupt framework gives a lot of information about each interrupt.
> 
> It does not keep track of when those interrupts occur though.
> 
> This patch provides a mean to record the elapsed time between successive
> interrupt occurrences in a per-IRQ per-CPU circular buffer to help with the
> prediction of the next occurrence using a statistical model.
> 
> A new function is added to browse the different interrupts and retrieve the
> timing information stored in it.
> 
> A static key is introduced so when the irq prediction is switched off at
> runtime, we can reduce the overhead near to zero. The irq timings is
> supposed to be potentially used by different sub-systems and for this reason
> the static key is a ref counter, so when the last use releases the irq
> timings that will result on the effective deactivation of the irq measurement.
> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> Acked-by: Nicolas Pitre <nicolas.pitre@...aro.org>
> ---
> V6:
>   - Renamed handle_irq_timings to record_irq_time
>   - Stored the event time instead of the interval time
>   - Removed the 'timestamp' field from the timings structure
>   - Moved _handle_irq_timings content inside record_irq_time

Looks fine to me.


Nicolas