Re: time slice cfq comments

[Jens Axboe <axboe@suse.de>]

On Sat, Dec 11 2004, Con Kolivas wrote:
> Hi Jens
> 
> Just thought I'd make a few comments about some of the code in your time 
> sliced cfq.
> 
> +	if (p->array)
> +		return min(cpu_curr(task_cpu(p))->time_slice,
> +					(unsigned int)MAX_SLEEP_AVG);
> 
> MAX_SLEEP_AVG is basically 10 * the average time_slice so this will 
> always return task_cpu(p)->time_slice as the min value (except for the 
> race you described in your comments). What you probably want is
> 
> +		return min(cpu_curr(task_cpu(p))->time_slice,
> +					(unsigned int)DEF_TIMESLICE);
> 
> 
> Further down you do:
> +	/*
> +	 * for blocked tasks, return half of the average sleep time.
> +	 * (because this is the average sleep-time we'll see if we
> +	 * sample the period randomly.)
> +	 */
> +	return NS_TO_JIFFIES(p->sleep_avg) / 2;
> 
> unfortunately p->sleep_avg is a non-linear value (weighted upwards 
> towards MAX_SLEEP_AVG). I suspect here you want
> 
> +	return NS_TO_JIFFIES(p->sleep_avg) / MAX_BONUS;
> 
> I don't see any need for / 2.

Ingo donoted that code, perhaps he would like to comment?

-- 
Jens Axboe