Re: Prevent auto scan in wireless devices

[Marc Herbert <Marc Herbert gmail com>]

Dan Williams <dcbw redhat com> writes:

> On Tue, 2009-01-13 at 17:45 -0300, Aloisio Almeida wrote:
>
>  Can you get some quantifiable
> power measurements on whether scanning (for both active and passive)
> *really* make a large difference here?  Chips are good enough these days
> that scanning doesn't really draw more power than having the chip awake.


Actually I found this discussion in Google while trying to understand
why powertop was going crazy since I finally (tried to) move from
ifupdown to NetworkManager.


- ifdown eth1

   => my CPU is in C4 state for 99.7 % of the time.

- NetworkManager.DisableWireless()

  => my CPU is now in C4 state for only 96% of the time, because my wireless
     driver throws 90 interrupts per second, because it keeps scanning.


I am not saying the problem belongs to NetworkManager. But as a plain
stupid luser who is not interested in who is responsible for what, the
move to NetworkManager resulted in a power regression. And by the way
it took me some significant effort to finally understand what was
going on.

You could answer that my wireless driver is buggy to throw so many
interruptions. Maybe. Sorry, but this is the only driver I (and a few
other millions of users) have. We would really appreciate if you could
avoid exposing a bug who was prefectly hidden before.

You could answer that I should use an alternative tool to power down
my interface, like for instance a hardware switch. First not every one
has a hardware switch. Then a hardware switch does not run my polite
dispatcher.d scripts which clean-up remote resources. And finally I
would appreciate if you could make sure this "alternative power
management tool", whichever it is, is available and working well
before removing a feature that was working fine in ifupdown.


Sorry for taking the "write-only" stance of a stupid and ignorant
luser; I did it because I am afraid they do not pop up so often deep
down in here.

PS: NetworkManager is very promising and an order of magnitude more
user-friendly than ifupdown. Keep up the good work.