Re: [patch] forcedeth: fix the NAPI poll function

[Jeff Garzik <jeff@garzik.org>]

Ingo Molnar wrote:
> * Jeff Garzik <jeff@garzik.org> wrote:
>
> > > FYI, looks good so far, ontop of Linus' latest -git tree.
> > >
> > > btw., one thing i always found weird about forcedeth is that it 
> > > generates an extra ~100 irqs per second even when there's no network 
> > > traffic:
> > >
> > > 11:      89752    XT-PIC-XT        eth0
> > > 11:      89854    XT-PIC-XT        eth0
> > > 11:      89955    XT-PIC-XT        eth0
> > > 11:      90056    XT-PIC-XT        eth0
> > > 11:      90157    XT-PIC-XT        eth0
> > >
> > > (irq count snapshot every second). Just in case it's easy to fix ...
> >
> > May I presume that behavior occurs in both mainline and my fe-lock 
> > branch?
>
> correct.

Any chance of getting a quick comparison of forcedeth CPU usage in your 
setup, between old driver and fe-lock driver?

I'm curious about the effects of fe-lock on CPU usage, which NAPI is 
known to perturb (in positive or negative directions, depending on 
conditions).

I presume both drivers can work at wire speed, sans any "too many 
iterations" problems...


> > That is likely the NIC's timer irq, which is programmed to kick the 
> > irq handler every so often.  DEV_NEED_TIMERIRQ is a starting point, as 
> > well as "Known bugs" at the top of forcedeth.c, if you're curious.
> >
> > I'm _betting_ that some of that can be eliminated, but we'll see...
>
> ok. Was just a FYI - you were looking for feedback :-)

Thanks!  :)

	Jeff


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