linux-kernel - Re: [RFC][PATCH 12/12] PM / r8169: Add simplified run-time PM support

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Message-Id: <201001032201.14087.rjw@sisk.pl>
Date:	Sun, 3 Jan 2010 22:01:14 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Pavel Machek <pavel@....cz>
Cc:	pm list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PCI <linux-pci@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Oliver Neukum <oliver@...kum.org>,
	Shaohua Li <shaohua.li@...el.com>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	Francois Romieu <romieu@...zoreil.com>,
	Len Brown <lenb@...nel.org>
Subject: Re: [RFC][PATCH 12/12] PM / r8169: Add simplified run-time PM support

On Sunday 03 January 2010, Pavel Machek wrote:
> 
> > > On notebooks, you can often use
> > > 
> > > pavel@amd:/data/l/linux-msm/arch/arm/mach-msm$ cat
> > > /proc/acpi/battery/BAT0/state 
> > > present:                 yes
> > > capacity state:          ok
> > > charging state:          charged
> > > present rate:            0 mW
> > > remaining capacity:      71830 mWh
> > > present voltage:         16277 mV
> > > 
> > > ...present rate is often usable-enough.
> > 
> > Using /proc/acpi/battery/BAT1/state I measured the energy drawn in 10 minutes
> > both with the network adapter in D0 and D3hot.  The results were that with the
> > network adapter in D0 the box drew 2476 mWh, while with the network adapter in
> > D3hot it drew 2361 mWh.  The difference is 115 mWh, or about 5% on this
> > particular box.
> > 
> > This means about 0.1 Wh in 10 minutes, so we can save about 0.6 Wh per hour.
> 
> Which means it saves 0.6W :-). Measuring power in Wh/h is "interesting".

You can't save power, you can only save energy.  Wh is just an energy unit.

> Ok, that's consistent with my experiments, ethernet transciever was around 1W... Thanks.

No big deal.

Rafael
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