Re: [PATCH] Fixes spurious system load spikes in /proc/loadavgrt

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On Thu, 2007-08-16 at 21:37 -0300, Luis Claudio R. Goncalves wrote:
> Hello,
> 
> The values in /proc/loadavgrt are sometimes the real load and sometimes
> garbage. As you can see in th tests below, it occurs from in 2.6.21.5-rt20 
> to 2.6.23-rc2-rt2. The code for calc_load(), in kernel/timer.c has not
> changed much in -rt patches.

> 
> Signed-off-by: Luis Claudio R. Goncalves <lclaudio@xxxxxxxx>
> ---
> 
> diff --git a/kernel/sched.c b/kernel/sched.c
> index 811a502..c61609a 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -2520,6 +2520,13 @@ unsigned long rt_nr_uninterruptible(void)
>  	for_each_online_cpu(i)
>  		sum += cpu_rq(i)->rt_nr_uninterruptible;
>  
> +	/*
> +	 * Since we read the counters lockless, it might be slightly
> +	 * inaccurate. Do not allow it to go below zero though:
> +	 */
> +	if (unlikely((long)sum < 0))
> +		sum = 0;
> +
>  	return sum;
>  }
>  
> diff --git a/linux-2.6.21.x86_64/kernel/timer.c b/linux-2.6.21.x86_64_lc/kernel/timer.c
> index 882ca9d..0e49bf6 100644
> --- a/linux-2.6.21.x86_64/kernel/timer.c
> +++ b/linux-2.6.21.x86_64_lc/kernel/timer.c
> @@ -1432,23 +1432,25 @@ unsigned long avenrun_rt[3];
>  static inline void calc_load(unsigned long ticks)
>  {
>  	unsigned long active_tasks; /* fixed-point */
> +	unsigned long active_rt_tasks; /* fixed-point */
>  	static int count = LOAD_FREQ;
>  
>  	count -= ticks;
>  	if (unlikely(count < 0)) {
>  		active_tasks = count_active_tasks();
> +		active_rt_tasks = count_active_rt_tasks();

Where is this used?

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