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

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Message-ID: <d6b7203d11aac2d83ddcd181f05a6074388d32d4.camel@linux.intel.com>
Date: Mon, 22 Jan 2024 15:33:27 -0800
From: Tim Chen <tim.c.chen@...ux.intel.com>
To: Frederic Weisbecker <frederic@...nel.org>
Cc: Heiko Carstens <hca@...ux.ibm.com>, Thomas Gleixner
 <tglx@...utronix.de>,  Ingo Molnar <mingo@...nel.org>, 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, 2024-01-22 at 23:31 +0100, Frederic Weisbecker wrote:
> Le Mon, Jan 22, 2024 at 10:19:30AM -0800, Tim Chen a écrit :
> > 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.
> 
> I guess those can be saved as well. Would you like to send the patch?
> 

Okay, sent the patch in a separate email.

Tim