Re: Help! I lost my C4 states :-)

[Stefan Seyfried <seife-bro8zJjCcIc@public.gmane.org>]

On Thu, Mar 03, 2005 at 04:38:49PM -0500, Len Brown wrote:
> On Mon, 2005-02-21 at 03:12, Stefan Seyfried wrote:

> > Any hints on how to track down what is causing bus master activity all the
> > time?
> > Has the calculation algorithm changed? Any default settings i could tweak?
> 
> Did you notice a battery life decrease with this decrease in C4
> residency?

Yes, although i lately run the battery down only on rare occasions, but the
"projected" runtime with mostly C4 active was almost 4 hours while now it is
a bit more than 3h30. I do no longer spin down the disk, since my dell locks
up hard sometimes when the disk should spin up again, but the C4 was at least
as big a gain than doing really aggressive disk spindown, (including 
laptop_mode etc, my disk was _really_ spun down for 10 minutes between short
spinups).

In fact, i noticed that C4 started working since i noticed that my battery
started to last longer. When i still spun down the disk, this was hardly
noticeable.
 
> On January 20th we pushed Dominik's jiffies based bm_activity patch
> in drivers/acpi/processor_idle.c  You might find that backing out
> that file a couple of revisions restores the previous behaviour.
> 
> Just after that, I added a tunable that you can tweak --
> with 1000 HZ, its default is all bits enabled, but
> you can reduce this bit mask to make the driver
> ignore less recent history:
> 
> # echo 0 > /sys/module/processor/parameters/bm_history
> 
> Will cause the processor driver to ignore the bus master activity
> completely.  Note that this could cause a performance hit if
> there is BM activity since will just pop the system out of C4
> and no instructions are executed during the transition out of C4.

I tried fiddling with this parameter, but will try again. I think i never
set it to zero, only 0xffff or something like that.
> 
> cheers,
> -Len
> 
> ps.
> If you're tracking battery life, I'd be interested to know if
> you notice a difference between when you build with HZ=100 and HZ=1000.

I'll do it as soon as Andrea Arcangely puts back the "select HZ Patch" back
into the SUSE kernel. Unfortunately i mostly have to run stock compiled
kernels just to be able to file "valid" bugreports :-)
-- 
Stefan Seyfried


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