linux-kernel - Re: [PATCH] tick-sched: fix idle and iowait sleeptime accounting vs CPU hotplug

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Message-ID: <0928660b39aea2828a79a87fef57447e657d43b4.camel@linux.intel.com>
Date: Mon, 22 Jan 2024 10:19:30 -0800
From: Tim Chen <tim.c.chen@...ux.intel.com>
To: Heiko Carstens <hca@...ux.ibm.com>, Frederic Weisbecker
	 <frederic@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar
	 <mingo@...nel.org>
Cc: Gerald Schaefer <gerald.schaefer@...ux.ibm.com>, Alexander Gordeev
	 <agordeev@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, 
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org
Subject: Re: [PATCH] tick-sched: fix idle and iowait sleeptime accounting vs
 CPU hotplug

On Mon, 2024-01-15 at 17:35 +0100, Heiko Carstens wrote:
> 
>  
> +	idle_sleeptime = ts->idle_sleeptime;
> +	iowait_sleeptime = ts->iowait_sleeptime;
>  	memset(ts, 0, sizeof(*ts));
> +	ts->idle_sleeptime = idle_sleeptime;
> +	ts->iowait_sleeptime = iowait_sleeptime;
>  }

Should idle_calls and idle_sleeps be preserved and
restored too?  

Seems like if we preserve the
idle_sleeptime, and wish to compute the average
sleep time per sleep, we will need to know the value of
idle_sleeps that's also preserved across CPU offline/online.

Tim