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

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Date:   Wed, 28 Mar 2018 12:56:42 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Thomas Ilsche <thomas.ilsche@...dresden.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul McKenney <paulmck@...ux.vnet.ibm.com>,
        Doug Smythies <dsmythies@...us.net>,
        Rik van Riel <riel@...riel.com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Mike Galbraith <mgalbraith@...e.de>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFT][PATCH v7 6/8] sched: idle: Select idle state before
 stopping the tick

On Wed, Mar 28, 2018 at 12:37 PM, Rafael J. Wysocki <rafael@...nel.org> wrote:
> On Wed, Mar 28, 2018 at 10:38 AM, Thomas Ilsche
> <thomas.ilsche@...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.