Interrupts + Polling mode (similar to Linux's NAPI)

[Erik Trulsson]

On Wed, Apr 29, 2009 at 05:46:32AM -0700, Barney Cordoba wrote:
> 
> 
> 
> 
> --- On Tue, 4/28/09, Andrew Snow <andrew at modulus.org> wrote:
> 
> > From: Andrew Snow <andrew at modulus.org>
> > Subject: Re: Interrupts + Polling mode (similar to Linux's NAPI)
> > To: "Luigi Rizzo" <rizzo at iet.unipi.it>
> > Cc: "FreeBSD Net" <freebsd-net at freebsd.org>
> > Date: Tuesday, April 28, 2009, 5:09 PM
> > Luigi Rizzo wrote:
> > > If i am not mistaken we don't have generic support
> > for interrupt moderation
> > > in the kernel but that's a specific NIC feature:
> > it works if the
> > > hardware supports it, and it doesn't otherwise.
> > > 
> > > Of course it would be possible to modify polling to
> > implement
> > > generic interrupt mitigation even without hardware
> > support, so
> > > you get the best of the two worlds.
> > 
> > It seems to me that you're wasting your time if you are
> > trying to achieve a high throughput in FreeBSD without using
> > an Intel Pro/1000 or 10gbe networking card.
> > 
> > So I don't know if anyone would really miss out if
> > generic polling support was completely removed from the
> > kernel and all efforts were then placed into improving other
> > parts of network flow in the kernel which need more help.
> > 
> > 
> > - Andrew
> 
> I'm not sure if those specific NICs are the "only" choices. But I am 
> concerned that so much brainpower is being put to extending the life
> of antiquated science projects and so little (maybe none?) is being
> put to improving drivers and the general network threading and
> performance.
> 
> You spend 3 years redesigning the kernel, yet there are no resources to
> create a decent 10gb/s solution, to get rid of netgraph and to do
> network integration properly, or to improve the large number of mediocre
> drivers that were written what might as well be 100 years ago.

If you think that more resources should be applied on certain areas, then
feel free to provide said resources yourself.  Other people are unlikely to
change what they work on just because you want them to.

> 
> When the collective answer to better network performance is polling, it
> makes it appear as if the FreeBSD project is a bunch of dudes working on
> stuff they feel like doing, rather than there being some centralized plan
> to make the project successful.

That appearance is probably due to the fact the the FreeBSD project actually
is a bunch of dudes working on what they feel like doing (or in a few cases
on what they get paid for doing), and that there is very little centralized
planning being done. (And even if there was, there is no way of enforcing
that people work according to such a plan.)



-- 
<Insert your favourite quote here.>
Erik Trulsson
ertr1013 at student.uu.se