Re: [RFT][PATCH v7 6/8] sched: idle: Select idle state before stopping the tick

From: Thomas Ilsche <thomas.ilsche@tu-dresden.de>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Linux PM <linux-pm@vger.kernel.org>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	Paul McKenney <paulmck@linux.vnet.ibm.com>,
	Doug Smythies <dsmythies@telus.net>,
	Rik van Riel <riel@surriel.com>,
	"Aubrey Li" <aubrey.li@linux.intel.com>,
	Mike Galbraith <mgalbraith@suse.de>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFT][PATCH v7 6/8] sched: idle: Select idle state before stopping the tick
Date: Wed, 28 Mar 2018 17:15:11 +0200	[thread overview]
Message-ID: <ceb8f46f-6bcd-a07e-beb4-b34a9810ad8d@tu-dresden.de> (raw)
In-Reply-To: <CAJZ5v0h40DDZ5da7CS4702Z=D3bY7SsOhbUqPR44qVKU0E4D4A@mail.gmail.com>

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On 2018-03-28 12:56, Rafael J. Wysocki wrote:
> On Wed, Mar 28, 2018 at 12:37 PM, Rafael J. Wysocki <rafael@kernel.org> wrote:
>> On Wed, Mar 28, 2018 at 10:38 AM, Thomas Ilsche
>> <thomas.ilsche@tu-dresden.de> wrote:
>>> On 2018-03-28 10:13, Rafael J. Wysocki wrote:
>>>>
> 
> [cut]
> 
>>
>> So I do
>>
>> $ for cpu in 0 1 2 3; do taskset -c $cpu sh -c 'while true; do usleep
>> 500; done' & done
>>
>> which is a shell kind of imitation of the above and I cannot see this
>> issue at all.
>>
>> I count the number of times data->next_timer_us in menu_select() is
>> greater than TICK_USEC and while this "workload" is running, that
>> number is exactly 0.
>>
>> I'll try with a C program still.
> 
> And with a C program I see data->next_timer_us greater than TICK_USEC
> while it is running, so let me dig deeper.
> 

I can confirm that a shell-loop behaves differently like you describe.
Even if it's just a shell-loop calling "main{usleep(500);}" binary.

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