On Thu, Oct 28, 2010 at 03:09:04PM -0700, Andrew Morton wrote:
> 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.
>
Fair point, I'll know for future reference. Thanks
>
> > for_each_online_cpu(cpu)
> > per_cpu_ptr(zone->pageset, cpu)->stat_threshold
> > = threshold;
>
--
Mel Gorman
Part-time Phd Student Linux Technology Center
University of Limerick IBM Dublin Software Lab
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