On Thu 17-05-12 23:56:45, Peter Zijlstra wrote:
> On Tue, 2012-05-15 at 17:43 +0200, Jan Kara wrote:
> > +void fprop_fraction_percpu(struct fprop_global *p,
> > + struct fprop_local_percpu *pl,
> > + unsigned long *numerator, unsigned long *denominator)
> > +{
> > + unsigned int seq;
> > + s64 den;
> > +
> > + do {
> > + seq = read_seqcount_begin(&p->sequence);
> > + fprop_reflect_period_percpu(p, pl);
> > + *numerator = percpu_counter_read_positive(&pl->events);
> > + den = percpu_counter_read(&p->events);
> > + if (den <= 0)
> > + den = percpu_counter_sum(&p->events);
> > + *denominator = den;
> > + } while (read_seqcount_retry(&p->sequence, seq));
> > +}
>
>
> why not use percpu_counter_read_positive(&p->events) and ditch
> percpu_counter_sum()? That sum can be terribly expensive..
Yes. I'm actually not sure why I used the _sum here... Thanks for
spotting this.
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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