linux-kernel - Re: [RFD 1/9] Change cpustat fields to an array.

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Message-ID: <1317157252.21836.3.camel@twins>
Date:	Tue, 27 Sep 2011 23:00:52 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Glauber Costa <glommer@...allels.com>
Cc:	linux-kernel@...r.kernel.org, paul@...lmenage.org,
	lizf@...fujitsu.com, daniel.lezcano@...e.fr,
	jbottomley@...allels.com
Subject: Re: [RFD 1/9] Change cpustat fields to an array.

On Fri, 2011-09-23 at 19:20 -0300, Glauber Costa wrote:
>  /* Must have preemption disabled for this to be meaningful. */
> -#define kstat_this_cpu __get_cpu_var(kstat)
> +#define kstat_this_cpu this_cpu_ptr(task_group_kstat(current))

This just lost you a debug check, the former would whinge when called
without preemption, the new one wont. Its part of the this_cpu feature
set to make debugging impossible.

> +#else
> +#define kstat_cpu(cpu) per_cpu(kstat, cpu)
> +#define kstat_this_cpu (&__get_cpu_var(kstat))
> +#endif
>  
>  extern unsigned long long nr_context_switches(void);
>  
> @@ -52,8 +62,8 @@ struct irq_desc;
>  static inline void kstat_incr_irqs_this_cpu(unsigned int irq,
>                                             struct irq_desc *desc)
>  {
> -       __this_cpu_inc(kstat.irqs[irq]);
> -       __this_cpu_inc(kstat.irqs_sum);
> +       kstat_this_cpu->irqs[irq]++;
> +       kstat_this_cpu->irqs_sum++;

It might be worth looking at the asm output of that, I think you made it
worse, but I'm not quite sure how smart gcc is, it might just figure out
what you meant.

>  } 
--
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