Re: [PATCH 2/3] percpu_stats: Simple per-cpu statistics count helper functions

[Christoph Lameter]

On Mon, 4 Apr 2016, Waiman Long wrote:

> > > +	if ((unsigned int)stat>= pcs->nstats)
> > > +		return;
> > > +	preempt_disable();
> > > +	pstat = this_cpu_ptr(&pcs->stats[stat]);
> > > +	*pstat += cnt;
> > > +	preempt_enable();
> > > +}
> > pstat = get_cpu_ptr(&pcs->stats[stat]);
> > *pstat += cnt;
> > put_cpu_ptr(&pcs->stats[stat]);
> >
> > It will generate identical code but this one uses APIs, making the
> > intention clearer. But as I said this is just a minor nit.
> >
> > you can add my Reviewed-by: Nikolay Borisov<kernel@xxxxxxxx>  for this
> > particular patch.
>
> Yes, that will certainly make it look nicer. I will update the patch once I
> get feedback from my other ext4 patches.

Why not

   this_cpu_add(pci->stats[stat], cnt)

This is a single instruction on x86.