Re: [RFC][ only for review ] memory controller bacground reclaim [3/5] high/low watermark support in res_counter

[yamamoto-jCdQPDEk3idL9jVzuh4AOg@public.gmane.org (YAMAMOTO Takashi)]

> This patch adds high/low watermark parameter to res_counter.
> splitted out from YAMAMOTO's background page reclaim for memory cgroup set.

thanks.

> +	 * Watermarks
> +	 * Should be changed automatically when the limit is changed and
> +	 * keep low < high < limit.
> +	 */
> +	unsigned long long high_watermark;
> +	unsigned long long low_watermark;
> +	/*

do you have any specific reason not to allow low == high == limit?
if you want to ensure low < high < limit, it's better to make the
default values below meet the condition as well.
to me, it seems weird to prevent users from making these values back to
the default.

YAMAMOTO Takashi

> @@ -17,6 +17,9 @@
>  {
>  	spin_lock_init(&counter->lock);
>  	counter->limit = (unsigned long long)LLONG_MAX;
> +	counter->low_watermark = (unsigned long long)LLONG_MAX;
> +	counter->high_watermark = (unsigned long long)LLONG_MAX;
> +	counter->watermark_state = RES_WATERMARK_BELOW_LOW;
>  }
>  
>  int res_counter_charge_locked(struct res_counter *counter, unsigned long val)