Re: reading files in /proc/acpi hangs machine for a short time

Michael Frank
2004-06-25T11:29:54Z

On Fri, 25 Jun 2004 08:29:29 +0200, wwp <subscript-GANU6spQydw@public.gmane.org> wrote:

> Hi there,
>
>
> many acpi programs that show the battery/etc. usage that I tested are making
> my system not to respond for a very short while, but periodically. For
> instance, the mouse is being locked for 1/n of a second, which is not a big
> loss of performance, but it really damn itchy for a normal (intensive) usage
> of my Dell Inspiron 8200 laptop (kernel 2.4.26). I do remember of some
> programs that were not producing such itchyness a long time ago (maybe
> because the kernel things were different?).
>
> I've found that if I some files from /proc/acpi (let's say battery state), I
> get the same behaviour.
>
> So my questions are:
> - is this a known issue?
> - program/kernel/dsdt/what-else issued?
> - are there known workarounds?
> - is it possible to get the acpi states from another place that /proc (if only it
> doesn't show the same problem)?
>

First figure out whether it is the PM app or ACPI.

1) Disable all PM apps touching /proc/acpi.

2) In a seperate terminal or VT run a script like

while :; do cat /proc/acpi/xxx/xxx/what_you_want_to_test > /dev/null; usleep 300000; done

Example sleeps 300ms (300000us) after every read, try various settings
from as low as 100ms to 10s and see how you system behaves.

If you don't have usleep sleep will do in 1s increments...

Note also can try cat /proc/acpi/battery/*/*

Run it continuously in the background and hopefully the test will show problems
due to ACPI proc accesses. If not, the PM apps are the problem - are these running
big scripts or impose high system load somehow?

Regards