Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1607832

Re: [PATCH V8 2/3] irq: Track the interrupt timings

From Thomas Gleixner <tglx@linutronix.de>
Newsgroups linux.kernel
Subject Re: [PATCH V8 2/3] irq: Track the interrupt timings
Date 2017-03-23 20:40 +0100
Message-ID <togKu-6RO-5@gated-at.bofh.it> (permalink)
References <tof22-5ye-13@gated-at.bofh.it> <tof22-5ye-11@gated-at.bofh.it> <togr8-6L0-19@gated-at.bofh.it>
Organization linux.* mail to news gateway

Show all headers | View raw

On Thu, 23 Mar 2017, Nicolas Pitre wrote:

> On Thu, 23 Mar 2017, Daniel Lezcano wrote:
> 
> > +#define IRQ_TIMINGS_SHIFT	5
> > +#define IRQ_TIMINGS_SIZE	(1 << IRQ_TIMINGS_SHIFT)
> > +#define IRQ_TIMINGS_MASK	(IRQ_TIMINGS_SIZE - 1)
> > +
> > +struct irq_timing {
> > +	u32 irq;
> > +	u64 ts;
> > +};
> > +
> > +struct irq_timings {
> > +	struct irq_timing values[IRQ_TIMINGS_SIZE]; /* our circular buffer */
> 
> This is not very space efficient because of alignment restrictions from 
> the u64 in struct irq_timing. 25% of the memory is wasted.
> 
> You could consider having two arrays instead:
> 
> 	u32 irq_values[IRQ_TIMINGS_SIZE];
> 	u64 ts_values[IRQ_TIMINGS_SIZE];

For the penalty of dirtying two cachelines instead of one.

Thanks,

	tglx

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH V8 2/3] irq: Track the interrupt timings Daniel Lezcano <daniel.lezcano@linaro.org> - 2017-03-23 18:50 +0100
  Re: [PATCH V8 2/3] irq: Track the interrupt timings Peter Zijlstra <peterz@infradead.org> - 2017-03-23 19:40 +0100
    Re: [PATCH V8 2/3] irq: Track the interrupt timings Nicolas Pitre <nicolas.pitre@linaro.org> - 2017-03-23 20:10 +0100
    Re: [PATCH V8 2/3] irq: Track the interrupt timings Daniel Lezcano <daniel.lezcano@linaro.org> - 2017-03-23 20:10 +0100
  Re: [PATCH V8 2/3] irq: Track the interrupt timings Nicolas Pitre <nicolas.pitre@linaro.org> - 2017-03-23 20:20 +0100
    Re: [PATCH V8 2/3] irq: Track the interrupt timings Thomas Gleixner <tglx@linutronix.de> - 2017-03-23 20:40 +0100
      Re: [PATCH V8 2/3] irq: Track the interrupt timings Nicolas Pitre <nicolas.pitre@linaro.org> - 2017-03-23 21:00 +0100
        Re: [PATCH V8 2/3] irq: Track the interrupt timings Thomas Gleixner <tglx@linutronix.de> - 2017-03-23 22:20 +0100

csiph-web