linux-kernel - Re: [linux-pm] [PATCH] pm: Add runtime PM statistics to sysfs

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Date:	Fri, 9 Jul 2010 11:11:06 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Arjan van de Ven <arjan@...radead.org>
cc:	linux-pm@...ts.linux-foundation.org, <linux-kernel@...r.kernel.org>
Subject: Re: [linux-pm] [PATCH] pm: Add runtime PM statistics to sysfs

On Fri, 9 Jul 2010, Alan Stern wrote:

> On Thu, 8 Jul 2010, Arjan van de Ven wrote:
> 
> > From: Arjan van de Ven <arjan@...ux.intel.com>
> > Subject: pm: Add runtime PM statistics to sysfs
> > 
> > In order for PowerTOP to be able to report how well the new runtime PM is working
> > for the various drivers, the kernel needs to export some basic statistics in sysfs.
> > 
> > This patch adds two sysfs files in the runtime PM domain that expose the
> > total time a device has been active, and the time a device has been suspended.
> > 
> > With this PowerTOP can compute the activity percentage
> > 
> > Active %age = 100 * (delta active) / (delta active + delta suspended)
> > 
> > and present the information to the user.
> > 
> > I've written the PowerTOP code (slated for version 1.12) already, and the output looks
> > like this:
> > 
> > Runtime Device Power Management statistics
> > Active  Device name
> >  10.0%	06:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8101E/RTL8102E
> 
> 
> > @@ -411,6 +433,7 @@ int __pm_runtime_resume(struct device *dev, bool from_wq)
> >  	}
> >  
> >  	if (retval) {
> > +		update_pm_runtime_accounting(dev);
> >  		dev->power.runtime_status = RPM_SUSPENDED;
> >  		pm_runtime_cancel_pending(dev);
> >  	} else {
> 
> This line was added in the wrong place.  It belongs either before the 
> "if (retval) {" or after the "} else {".

Whoops, sorry, my mistake.  It doesn't belong here at all.  It belongs 
considerably earlier in the function, before the line:

	dev->power.runtime_status = RPM_RESUMING;

This is because update_pm_runtime_accounting() doesn't take into 
account the existence of the RPM_RESUMING and RPM_SUSPENDING states; it 
treats them all the same as RPM_ACTIVE.

Also, it looks like you forgot to add a call in 
__pm_runtime_set_status().

Alan Stern

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