Re: [PATCH 8/9] psi: pressure stall information for CPU, memory, and IO

[Peter Zijlstra]

On Mon, Aug 06, 2018 at 11:19:28AM -0400, Johannes Weiner wrote:
> On Fri, Aug 03, 2018 at 06:56:41PM +0200, Peter Zijlstra wrote:
> > On Wed, Aug 01, 2018 at 11:19:57AM -0400, Johannes Weiner wrote:

> > > +		u32 uninitialized_var(nonidle);
> > 
> > urgh.. I can see why the compiler got confused. Dodgy :-)
> 
> :-) I think we can make this cleaner. Something like this (modulo the
> READ_ONCE/WRITE_ONCE you pointed out in the other email)?
> 

> @@ -244,60 +287,17 @@ static bool psi_update_stats(struct psi_group *group)
>  	 */
>  	for_each_online_cpu(cpu) {
>  		struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
> +		u32 nonidle;
> +
> +		nonidle = read_update_delta(groupc, PSI_NONIDLE, cpu);
> +		nonidle = nsecs_to_jiffies(nonidle);
> +		nonidle_total += nonidle;
> +
> +		for (s = 0; s < PSI_NONIDLE; s++) {
> +			u32 delta;
> +
> +			delta = read_update_delta(groupc, s, cpu);
> +			deltas[s] += (u64)delta * nonidle;
>  		}
>  	}

Yes, much clearer, thanks!