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Date: Mon, 19 Jan 2026 23:08:38 +0100
From: Frederic Weisbecker <frederic@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	"Christophe Leroy (CS GROUP)" <chleroy@kernel.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
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	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Heiko Carstens <hca@linux.ibm.com>, Ingo Molnar <mingo@redhat.com>,
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	Xin Zhao <jackzxcui1989@163.com>, linux-pm@vger.kernel.org,
	linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 09/15] tick/sched: Move dyntick-idle cputime accounting
 to cputime code
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References: <20260116145208.87445-1-frederic@kernel.org>
 <20260116145208.87445-10-frederic@kernel.org>
 <20260119143552.GH830229@noisy.programming.kicks-ass.net>
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Le Mon, Jan 19, 2026 at 03:35:52PM +0100, Peter Zijlstra a écrit :
> On Fri, Jan 16, 2026 at 03:52:02PM +0100, Frederic Weisbecker wrote:
> 
> > +static void kcpustat_idle_stop(struct kernel_cpustat *kc, ktime_t now)
> >  {
> > +	u64 *cpustat = kc->cpustat;
> > +	ktime_t delta;
> > +
> > +	if (!kc->idle_elapse)
> > +		return;
> > +
> > +	delta = ktime_sub(now, kc->idle_entrytime);
> > +
> > +	write_seqcount_begin(&kc->idle_sleeptime_seq);
> > +	if (nr_iowait_cpu(smp_processor_id()) > 0)
> > +		cpustat[CPUTIME_IOWAIT] = ktime_add(cpustat[CPUTIME_IOWAIT], delta);
> > +	else
> > +		cpustat[CPUTIME_IDLE] = ktime_add(cpustat[CPUTIME_IDLE], delta);
> > +
> > +	kc->idle_entrytime = now;
> > +	kc->idle_elapse = false;
> > +	write_seqcount_end(&kc->idle_sleeptime_seq);
> >  }
> 
> I realize this is mostly code movement; but do we really want to
> preserve ktime_{sub,add}() and all that?
> 
> I mean, we killed that 32bit ktime nonsense ages ago.

Good point, this should just be u64.

Thanks!

-- 
Frederic Weisbecker
SUSE Labs