Re: performance problems?

[Ducrot Bruno <ducrot-kk6yZipjEM5g9hUCZPvPmw@public.gmane.org>]

On Tue, Nov 19, 2002 at 10:59:43AM -0500, James D Strandboge wrote:
> On Tue, 2002-11-19 at 09:54, Markus Gaugusch wrote:
> > On Nov 19, Loic Jaquemet <ljaquemet-BNG0eM9rGRi0IRkH3yUr9EW4647UYGdYQQ4Iyu8u01E@public.gmane.org> wrote:
> > > i'am using 2.4.19 + around october patch ( I'll check that this evening )
> > > on sony vaio fx502
> > > [...]
> > > when I fetch the /proc/acpi/<batteriesxxx>/state|info files, I get a 1-2
> > > second freeze| lag ..
> > > [...]
> > > I'm not sure, but i think i didn't have this problem on pre-september
> > > patches ..
> > No, it has been present before. I have an FX405 and can't use any battery
> > monitor applet that reads the info file. Even a 'cat
> > /proc/acpi/battery/BAT1/info' causes a noticable peak in my cpu monitor
> > (kernel time). At least, it doesn't freeze keyboard anymore, thanks to the
> > ACPI people!
> > 
> 
> You want to poll /proc/acpi/battery/BAT1/state or whatever is correct
> for your battery.  Polling info requires interrupts with the BIOS I
> think, and state is there for a quick poll.  At least on my machine this
> is the case.  

Yes and not.  In fact, the ASL code contains some Notification() methods, then
kernel will inform user space via /proc/acpi/event.

Most of the time, those Notification() are generated by an interrupt (certainly
an SCI).
You should see some Notification() to the battery(ies) in a \_GPE.[EL]xx(), or in a
_Qxx() from an embedded controller in that case.

> 
> Perhaps someone would want to clarify the difference and why info causes
> a hang and state does not.

info give 'static' informations, as design capacity, last full technology, etc.
It is 'huge', and do not need to be read often.

state give the actual remaining capacity of the battery, present voltage, and so
on.  It is 'small' and also hold the 'variable' part of the battery.


Now why cat'ing 'info' hang some systems is another
problem (Should Not Happen (c)(tm))...


-- 
Ducrot Bruno
http://www.poupinou.org        Page profaissionelle
http://toto.tu-me-saoules.com  Haume page


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