On Wed, Mar 16, 2016 at 02:23:21PM +0100, Rafael J. Wysocki wrote:
> On Wed, Mar 16, 2016 at 2:10 PM, Peter Zijlstra <pet...@infradead.org> wrote:
> > (this would of course require we allocate struct update_util_data with
> > the proper alignment thingies etc..)
> > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > index ba49c9efd0b2..d34d75c5cc93 100644
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -3236,8 +3236,10 @@ static inline unsigned long rlimit_max(unsigned int
> > limit)
> >
> > #ifdef CONFIG_CPU_FREQ
> > struct update_util_data {
> > - void (*func)(struct update_util_data *data,
> > - u64 time, unsigned long util, unsigned long max);
> > + unsigned long *cfs_util_avg;
> > + unsigned long *cfs_util_max;
> > +
> > + void (*func)(struct update_util_data *data, u64 time);
> > };
we should add: ____cacheline_aligned here
> How do we ensure proper alignment?
Depends on the allocator; not all of them respect the struct alignment
attribute.
kernel/sched/cpufreq.c:DEFINE_PER_CPU(struct update_util_data *,
cpufreq_update_util_data);
That one could use:
DEFINE_PER_CPU_ALIGNED() instead
as would this one:
drivers/cpufreq/cpufreq_governor.c:static DEFINE_PER_CPU(struct cpu_dbs_info,
cpu_dbs);
Because when you cacheline align dbs_info, its update_util_data member
will also get the correct alignment because of the structure attribute.
