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

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Message-ID: <20060905090328.GA4888@elf.ucw.cz>
Date:	Tue, 5 Sep 2006 11:03:28 +0200
From:	Pavel Machek <pavel@....cz>
To:	abelay@...ell.com, 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

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?!

root@amd:/data/l/tp/tp_smapi-0.22# cat /proc/acpi/processor/CPU0/power
active state:            C3
max_cstate:              C8
bus master activity:     37244
states:
    C1:                  type[C1] latency[000] usage[00000067]
duration[00000000000000000067]
    C2:                  type[C2] latency[001] usage[00042173]
duration[00000000000454647687]
   *C3:                  type[C3] latency[057] usage[00290242]
duration[00000000003402855375]
root@amd:/data/l/tp/tp_smapi-0.22# cat /proc/acpi/processor/CPU0/power
active state:            C3
max_cstate:              C8
bus master activity:     37244
states:
    C1:                  type[C1] latency[000] usage[00000067]
duration[00000000000000000067]
    C2:                  type[C2] latency[001] usage[00042274]
duration[00000000000454688808]
   *C3:                  type[C3] latency[057] usage[00305466]
duration[00000000003595077816]
root@amd:/data/l/tp/tp_smapi-0.22#
								Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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