On Thu, 28 Oct 2010 16:13:36 +0100
Mel Gorman <mel@xxxxxxxxx> wrote:
> reduce_pgdat_percpu_threshold() and restore_pgdat_percpu_threshold()
> exist to adjust the per-cpu vmstat thresholds while kswapd is awake to
> avoid errors due to counter drift. The functions duplicate some code so
> this patch replaces them with a single set_pgdat_percpu_threshold() that
> takes a callback function to calculate the desired threshold as a
> parameter.
hm. Could have passed in some silly flag rather than a function
pointer but whatever.
>
> ...
>
> -void reduce_pgdat_percpu_threshold(pg_data_t *pgdat)
> +void set_pgdat_percpu_threshold(pg_data_t *pgdat,
> + int (*calculate_pressure)(struct zone *))
> {
> struct zone *zone;
> int cpu;
> @@ -196,28 +197,7 @@ void reduce_pgdat_percpu_threshold(pg_data_t *pgdat)
> if (!zone->percpu_drift_mark)
> continue;
>
> - threshold = calculate_pressure_threshold(zone);
> - for_each_online_cpu(cpu)
> - per_cpu_ptr(zone->pageset, cpu)->stat_threshold
> - = threshold;
> - }
> - put_online_cpus();
> -}
> -
> -void restore_pgdat_percpu_threshold(pg_data_t *pgdat)
> -{
> - struct zone *zone;
> - int cpu;
> - int threshold;
> - int i;
> -
> - get_online_cpus();
> - for (i = 0; i < pgdat->nr_zones; i++) {
> - zone = &pgdat->node_zones[i];
> - if (!zone->percpu_drift_mark)
> - continue;
> -
> - threshold = calculate_threshold(zone);
> + threshold = calculate_pressure(zone);
Readability nit: it's better to use the
threshold = (*calculate_pressure)(zone);
syntax here. So the code reader doesn't go running around trying to
find the function "calculate_pressure". I've been fooled that way
plenty of times.
> for_each_online_cpu(cpu)
> per_cpu_ptr(zone->pageset, cpu)->stat_threshold
> = threshold;
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