linux-kernel - Re: clocksource_watchdog causing scheduling of timers every second (was [v13] support "task

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Date:	Mon, 15 Aug 2016 11:03:54 -0400
From:	Chris Metcalf <cmetcalf@...lanox.com>
To:	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Christoph Lameter <cl@...ux.com>
CC:	Gilad Ben Yossef <giladb@...lanox.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	"Catalin Marinas" <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	"Andy Lutomirski" <luto@...capital.net>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	<linux-doc@...r.kernel.org>, <linux-api@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: clocksource_watchdog causing scheduling of timers every second
 (was [v13] support "task_isolation" mode)

On 8/11/2016 7:58 AM, Frederic Weisbecker wrote:
>> Arguably we should issue a boot time warning if NOHZ_FULL is configured
>> >and the TSC watchdog is running.
> That's a very good idea! We do that when tsc is unstable but indeed we can't
> seriously run NOHZ_FULL on a non-reliable tsc.
>
> I'll take care of that warning.

Thanks.  So I will drop Christoph's patch to run the TSC watchdog on just
housekeeping cores and we will rely on the "boot time warning" instead.

-- 
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com