RE: [PATCH] lan78xx: Protect runtime_auto check by #ifdef CONFIG_PM

[Alan Stern]

On Mon, 21 Mar 2016 Woojung.Huh@xxxxxxxxxxxxx wrote:

> > > > But this leaves open the issue that querying the device too often will
> > > > prevent it from going into autosuspend.  It seems to me that the best
> > > > way to deal with this is to make sure that the autosuspend timeout is
> > > > shorter than the interal between queries, not to make the querying
> > > > conditional on !runtime_auto.
> > >
> > > Short autosuspend timeout can affect performance. For instance our
> > experiments showed that
> > > shorter than 10sec timeout made Ethernet performance degrade because
> > of wakeup delays.
> > > So, just putting shorter timeout may have some side effects.
> > 
> > Sure.  This just means that you need a long statistics interval --
> > longer than the autosuspend timeout.  That's why I suggested making the
> > interval adjustable.
> 
> What do you mean statistics interval?
> Interval calling ndo_get_stats64 or another thread/timer or else getting statistics?

The time between calls to ndo_get_stats64, since that's the routine 
which queries the device.

Alan Stern