Adding Flow Director sysctls to ixgbe(4)

[Navdeep Parhar]

On Fri, Sep 09, 2011 at 01:44:34AM +0100, Ben Hutchings wrote:
> 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.

rwatson@ has been working on "connection groups" (not sure what he calls
his project) with a goal to improve the placement of work in the FreeBSD
network stack.  Some of the code is in the kernel but the parts that
require closer cooperation with a NIC are not.

Regards,
Navdeep