linux-kernel - Re: [RFC][PATCH 2/2] ACPI: handle timer ticks proactively

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Date:	Tue, 05 Sep 2006 11:16:00 -0400
From:	Adam Belay <abelay@...ell.com>
To:	Pavel Machek <pavel@....cz>
Cc:	len.brown@...el.com, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux@...inikbrodowski.net,
	arjan@...ux.intel.com
Subject: Re: [RFC][PATCH 2/2] ACPI: handle timer ticks proactively

On Tue, 2006-09-05 at 11:03 +0200, Pavel Machek wrote:
> Hi!
> 
> > > > This patch takes advantage of the infrastructure introduced in the last
> > > > patch, and allows the processor idle algorithm to proactively choose a
> > > > c-state based on the time the next timer interrupt is expected to occur.
> > > > It preserves the residency metric, so the algorithm should, in theory,
> > > > remain effective against bursts of activity from other interrupt
> > > > sources.
> > > > 
> > > > This patch is mostly intended to be illustrative.  There may be some
> > > > "#ifdef CONFIG_ACPI" issues, and I would appreciate any advice on
> > > > implementing this more cleanly.
> > 
> > Okay, just to get you some feedback:
> > 
> > It seems to change things a _lot_. Power consumption with usb modules
> > loaded went from 14315mW to 13800mW -- that is huge
> > deal. Unfortunately something strange is going on: with stock kernel,
> > power consumption is mostly constant. With your patch, it varies a
> > lot, at 2 second timescale.
> > 
> > Power consumption with usb unloaded (only way to get reasonable power
> > on x60) went from stable 10450mW to  something rapidly changing, and
> > probably even worse than original:
> 
> I also noticed that with your patch, bus master activity tends to be constant?!

Is this the case even when userspace touches the disk?  On my hardware I
see a constant flow of short BM activity bursts.

Thanks,
Adam


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