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

[Waiman Long]

On 04/04/2016 03:09 PM, Christoph Lameter wrote:
> 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.

Yes, using this_cpu_add() will be even simpler.

Cheers,
Longman