* Peter Zijlstra <pet...@infradead.org> wrote:
> On Fri, Sep 28, 2018 at 01:53:20PM -0400, Waiman Long wrote:
> > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> > index ca002c0..7a0ed1d 100644
> > --- a/kernel/locking/lockdep.c
> > +++ b/kernel/locking/lockdep.c
> > @@ -139,6 +139,7 @@ static inline int debug_locks_off_graph_unlock(void)
> > */
> > unsigned long nr_lock_classes;
> > static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
> > +static DEFINE_PER_CPU(unsigned long [MAX_LOCKDEP_KEYS], lock_class_ops);
>
> > @@ -1387,11 +1391,15 @@ static inline int usage_match(struct lock_list
> > *entry, void *bit)
> >
> > static void print_lock_class_header(struct lock_class *class, int depth)
> > {
> > - int bit;
> > + int bit, cpu;
> > + unsigned long ops = 0UL;
> > +
> > + for_each_possible_cpu(cpu)
> > + ops += *per_cpu(class->pops, cpu);
> >
> > printk("%*s->", depth, "");
> > print_lock_name(class);
> > - printk(KERN_CONT " ops: %lu", class->ops);
> > + printk(KERN_CONT " ops: %lu", ops);
> > printk(KERN_CONT " {\n");
> >
> > for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
>
> That is an aweful lot of storage for a stupid number. Some archs
> (sparc64) are bzImage size constrained and this will hurt them.
>
> Ingo, do you happen to remember what that number was good for?
Just a spur of the moment statistics to satisfy curiousity, and it's useful to
see how 'busy' a
particular class is, right?
> Can't we simply ditch it?
We certainly could. Do we have roughly equivalent metrics to arrive at this
number via other
methods?
Thanks,
Ingo
