linux-kernel - Re: [announce] Intel announces the PowerTOP utility for Linux

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Message-Id: <200705142142.07983.s0348365@sms.ed.ac.uk>
Date:	Mon, 14 May 2007 21:42:07 +0100
From:	Alistair John Strachan <s0348365@....ed.ac.uk>
To:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-acpi@...r.kernel.org
Subject: Re: [announce] Intel announces the PowerTOP utility for Linux

On Monday 14 May 2007 21:22:50 Jan Engelhardt wrote:
> On May 12 2007 22:12, Alistair John Strachan wrote:
> >On Saturday 12 May 2007 00:07:18 Arjan van de Ven wrote:
> >> What's eating the battery life of my laptop? Why isn't it many more
> >> hours? Which software component causes the most power to be burned?
> >> These are important questions without a good answer... until now.
> >
> >This is a really great tool and presents a very intuitive alternative to
> > the timer stats file..
> >
> >On a Core 2 Duo Macbook, Linux always gets around 3.2h battery, OS X about
> >4.2h. This tool has identified that uhci_hcd is where 75% of the ticks are
> >going when X is not loaded. Unloading uhci_hcd drops the battery life back
> > to around 4.2h, but I lose the keyboard.
> >
> >Is there any way to find out what USB driver is causing usb_uhci to be
> > this busy?
>
> At its worst, it _is_ the USB chip that draws the power when it is active
> (when uhci_hcd is loaded); does not need to be usbhid or so.

This is certainly true, and to a significant extent it _was_ the uhci_hcd, but 
it turns out the main contributor to HZ here were the appletouch and hci_usb 
drivers. Disabling both drops the ticks down from about 850 to 150.

-- 
Cheers,
Alistair.

Final year Computer Science undergraduate.
1F2 55 South Clerk Street, Edinburgh, UK.
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