linux-kernel - Re: [PATCH] sched/nohz: add debugfs control over sched_tick_max

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Message-ID: <7hh9zq31ia.fsf@deeprootsystems.com>
Date:	Mon, 29 Sep 2014 08:11:25 -0700
From:	Kevin Hilman <khilman@...nel.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH] sched/nohz: add debugfs control over sched_tick_max_deferment

Frederic Weisbecker <fweisbec@...il.com> writes:

> On Fri, Sep 26, 2014 at 12:45:32PM -0700, Kevin Hilman wrote:
>> From: Kevin Hilman <khilman@...aro.org>
>> 
>> Allow debugfs override of sched_tick_max_deferment in order to ease
>> finding/fixing the remaining issues with full nohz.
>> 
>> The value to be written is in jiffies, and -1 means the max deferment
>> is disabled (scheduler_tick_max_deferment() returns KTIME_MAX.)
>> 
>> Cc: Frederic Weisbecker <fweisbec@...il.com>
>> Signed-off-by: Kevin Hilman <khilman@...aro.org>
>
> So, I'm worried that it becomes a hack that everybody uses to shutdown
> the tick completely then nobody will come and fix the issue that prevents
> from doing it properly.

OK.

> I seriously doubt this will be used for development purpose to help
> fixing the real problem. 

Well, that's what I was using it for, until I was distracted by other
tasks.

> Quite the opposite. If developers want to do
> testing, they can as well comment out the call to scheduler_max_tick_deferment().

OK, fair enough.

Thanks,

Kevin
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