linux-kernel - Re: [PATCH V4] irq: Track the interrupt timings

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Message-ID: <20160422182146.GC3974@linaro.org>
Date:	Fri, 22 Apr 2016 20:21:46 +0200
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	tglx@...utronix.de
Cc:	nicolas.pitre@...aro.org, shreyas@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, peterz@...radead.org,
	rafael@...nel.org, vincent.guittot@...aro.org
Subject: Re: [PATCH V4] irq: Track the interrupt timings

On Wed, Apr 13, 2016 at 01:05:56PM +0200, 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>
> ---
> V4:
>   - Added a static key
>   - Added more comments for irq_timings_get_next()
>   - Unified some function names to be prefixed by 'irq_timings_...'
>   - Fixed a rebase error
> V3:
>   - Replaced ktime_get() by local_clock()
>   - Shared irq are not handled
>   - Simplified code by adding the timing in the irqdesc struct
>   - Added a function to browse the irq timings
> V2:
>   - Fixed kerneldoc comment
>   - Removed data field from the struct irq timing
>   - Changed the lock section comment
>   - Removed semi-colon style with empty stub
>   - Replaced macro by static inline
>   - Fixed static functions declaration
> RFC:
>   - initial posting
> ---

Hi Thomas,

do you think this patch is acceptable ?