linux-kernel - Re: [PATCH 00/15] tick/sched: Refactor idle cputime accounting

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Message-ID: <aXEE_5vT03dlTCyN@localhost.localdomain>
Date: Wed, 21 Jan 2026 17:55:27 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: Shrikanth Hegde <sshegde@...ux.ibm.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Boqun Feng <boqun.feng@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Christophe Leroy (CS GROUP)" <chleroy@...nel.org>,
	Kieran Bingham <kbingham@...nel.org>,
	Ben Segall <bsegall@...gle.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Ingo Molnar <mingo@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Xin Zhao <jackzxcui1989@....com>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Jan Kiszka <jan.kiszka@...mens.com>, linuxppc-dev@...ts.ozlabs.org,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Uladzislau Rezki <urezki@...il.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Heiko Carstens <hca@...ux.ibm.com>, linux-pm@...r.kernel.org,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Nicholas Piggin <npiggin@...il.com>, linux-s390@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 00/15] tick/sched: Refactor idle cputime accounting

Le Tue, Jan 20, 2026 at 06:12:08PM +0530, Shrikanth Hegde a écrit :
> 
> Hi Frederic.
> 
> On 1/16/26 8:27 PM, Frederic Weisbecker wrote:
> > I forgot to mention I haven't yet tested CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
> > (s390 and powerpc).
> > 
> > Thanks.
> 
> 
> tl;dr
> 
> I ran this on powerNV(Non virtualized) with 144 CPUs with below config. (default ones)
> Patch *breaks* the cpu idle stats most of the time. idle values are wrong.

Right I somehow lost the TS_FLAG_INIDLE setting in tick_nohz_idle_enter(),
which ruins the whole thing.

You probably think I should have detected that with light testing and you're
right. Not checking dmesg was a bit sloppy from my end...

I'm fixing that and will send a v2 soonish.

Thanks a lot for testing!

-- 
Frederic Weisbecker
SUSE Labs