linux-kernel - Re: [PATCH v13 00/12] support "task

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Message-ID: <7a3f66f7-5011-7d59-2e0e-f57e4e42e6b6@mellanox.com>
Date:	Fri, 22 Jul 2016 08:50:44 -0400
From:	Chris Metcalf <cmetcalf@...lanox.com>
To:	Christoph Lameter <cl@...ux.com>
CC:	Gilad Ben Yossef <giladb@...lanox.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rik van Riel" <riel@...hat.com>, Tejun Heo <tj@...nel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	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: [PATCH v13 00/12] support "task_isolation" mode

On 7/21/2016 10:20 PM, Christoph Lameter wrote:
> On Thu, 21 Jul 2016, Chris Metcalf wrote:
>> On 7/20/2016 10:04 PM, Christoph Lameter wrote:
>> unstable, and then scheduling work to safely remove that timer.
>> I haven't looked at this code before (in kernel/time/clocksource.c
>> under CONFIG_CLOCKSOURCE_WATCHDOG) since the timers on
>> arm64 and tile aren't unstable.  Is it possible to boot your machine
>> with a stable clocksource?
> It already as a stable clocksource. Sorry but that was one of the criteria
> for the server when we ordered them. Could this be clock adjustments?

We probably need to get clock folks to jump in on this thread!

Maybe it's disabling some built-in unstable clock just as part of
falling back to using the better, stable clock that you also have?
So maybe there's a way of just disabling that clocksource from the
get-go instead of having it be marked unstable later.

If you run the test again after this storm of unstable marking, does
it all happen again?  Or is it a persistent state in the kernel?
If so, maybe you can just arrange to get to that state before starting
your application's task-isolation code.

Or, if you think it's clock adjustments, perhaps running your test with
ntpd disabled would make it work better?

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