Adding Flow Director sysctls to ixgbe(4)

[Ben Hutchings]

On Thu, 2011-09-08 at 20:13 -0400, George Neville-Neil wrote:
> On Sep 8, 2011, at 14:49 , Navdeep Parhar wrote:
> 
> > On Thu, Sep 08, 2011 at 08:34:11AM -0400, John Baldwin wrote:
> >> On Monday, September 05, 2011 7:21:12 am Ben Hutchings wrote:
> >>> On Mon, 2011-09-05 at 15:51 +0900, Takuya ASADA wrote:
> >>>> Hi,
> >>>> 
> >>>> I implemented Ethernet Flow Director sysctls to ixgbe(4), here's a detail:
> >>>> 
> >>>> - Adding removing signature filter
> >>>> On linux version of ixgbe driver, it has ability to set/remove perfect
> >>>> filter from userland using ethtool command.
> >>>> I implemented similar feature, but on sysctl, and not perfect filter
> >>>> but signature filter(which means hash collision may occurs).
> >>> [...]
> >>> 
> >>> Linux also has a generic interface to RX filtering and hashing
> >>> (ethtool_rxnfc) which ixgbe supports; wouldn't it be better for FreeBSD
> >>> to support something like that?
> >> 
> >> Some sort of shared interface might be nice.  The cxgb(4) and cxgbe(4) drivers
> >> both provide their own tools to manipulate filters, though they do not
> >> provide explicit steering IIRC.
> > 
> > Both of them can filter as well as steer (and the tools let you do that).
> > cxgbe(4) can do a lot more (rewrite + switch, replicate, etc.) but those
> > features are perhaps too specialized to be configurable via a general
> > purpose tool.
> > 
> >> 
> >> We would need to come up with some sort of standard interface (ioctls?) for 
> >> adding filters however.
> > 
> > +1 for a standard interface.
> > 
> > imho the kernel needs to be aware of the rx and tx queues of a NIC, and
> > not just for steering.  But that's a separate discussion.
> > 
> 
> Well I do think this is actually all of a part.  Most of us realize by now that
> high speed (e.g. 10G and higher) NICs only make sense if you can steer traffic and
> pin queues to cores etc.

Well, you can get way better than 1G performance without that.  And for
routers, flow hashing may be fine.  But for a host, of course, steering
packets properly can provide a major performance win.

[...]
> What this means is that we have
> a failure of abstraction.  Abstraction has a cost, and some of the people who want
> access to low level queues are not interested in paying an extra abstraction cost.

Abstraction has a cost, but it's not necessarily that high compared to
rewriting a whole chunk of sockets code (especially if you don't
actually have the source code).

> I think that some of the abstractions we need are tied up in the work that Takuya did
> for SoC and some of it is in the work done by Luigi on netmap.  I'd go so far as to say
> that what we should do is try to combine those two pieces of code into a set of
> low level APIs for programs to interact with high speed NICs.  The one thing most
> people do not talk about is extending our socket API to do two things that I think would
> be a win for 80% of our users.  If a socket, and also a kqueue, could be pinned
> to a CPU as well as a NIC queue that should improve overall bandwidth for a large
> number of our users.  The API there is definitely an ioctl() and the hard part is
> doing the tying together.  To do this we need to also work out our low level story.

But it would be a lot nicer if this could be done automatically.  Which
I believe it can - see the RFS and XPS features in Linux.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.