Reasons to try the new USB driver (was: cpu.cx usage no longer available?)

[Fabian Keil]

"Kevin Oberman" <oberman at es.net> wrote:

> > Date: Wed, 2 May 2007 10:33:15 +1200
> > From: Andrew Thompson <thompsa at freebsd.org>
> > 
> > On Tue, May 01, 2007 at 03:13:38PM -0700, Kevin Oberman wrote:
> > > I just installed Hans Petter's new USB driver on my laptop and wanted to
> > > see if it still prevented the system from dropping into deeper sleep
> > > modes. In the past I was limited to C2 when USB was loaded.
> > > 
> > > Now I see only hw.acpi.cpu.cx_lowest. cx_usage and cx_supported seem to
> > > be gone.
> > > 
> > > I am running on a Pentium-M CPU, single core.
> > > 
> > > Do I need to enable something to make these show up or is there another
> > > way to get this information?
> > 
> > Its now a per-cpu setting, look at dev.cpu.0.cx_supported.
> 
> Ahh, yes. I knew this at one time, but I had forgotten it.
> 
> Looks like the man page is a bit out of date. If I get a few spare
> minutes I'll try to submit a patch.
> 
> I am VERY pleased to see that Hans Petter's new USB drivers do allow the
> system to drop into C3! It will require a bit more testing, but I hope
> to be able to leave USB in my kernel without serious battery life
> impact.
> 
> I have heard that the new USB drivers are unlikely to make it into V7.0
> due to lack of testing. I really hope a few more people give it a whirl
> and report back on the results, good or bad, so that the drivers can
> either be fixed or added to current.

I assume more people would test it if they knew
what the new USB driver does better than the old one.

I knew that a new USB driver existed, and that
it had some locking improvements, but so far I
didn't see any benchmarks. (I'm not subscribed to
freebsd-usb@, maybe they were only posted there.)

The last status report said:

|Some claim 2x improvements, others have seen more.
|But don't expect too much.

I (mis)interpreted that as "some claim a lot but don't expect anything". 

Now that I know that the new USB driver might increase
battery life I'm definitively going to give it try,
so maybe it would make sense to (re-)post some more
reasons or success stories on stable@ or current at .

Fabian
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