Re: [rfc 4/4] igb: expose 82576 bandiwidth allocation

[Simon Horman <horms@verge.net.au>]

On Thu, Nov 05, 2009 at 03:42:28PM -0800, Alexander Duyck wrote:
> Simon Horman wrote:
> >On Thu, Nov 05, 2009 at 03:00:02PM -0800, Alexander Duyck wrote:
> >>Simon Horman wrote:
> >>>The 82576 has support for bandwidth allocation to VFs.
> >>>
> >>>Contrary to the documentation in the 82576 datasheet v2.41 this
> >>>appears to work as follows:
> >>>
> >>>* The ratio supplied is always proportional to 1Gbit/s,
> >>> regardless of if the link speed.
> >>>* The ratio supplied is an upper-bound on bandwidth available
> >>> to the VF, not a minimun guarantee
> >>>
> >>>This patch exposes bandwidth control to userspace through a simple
> >>>per-device (PF) sysfs file, bandwidth_allocation.
> >>>
> >>>* The file contains a whitespace delimited list of values, one per VF.
> >>>* The first value corresponds to the first VF and so on.
> >>>* Valid values are integers from 0 to 1000
> >>>* A value of 0 indicates that bandwidth_allocation is disabled.
> >>>* Other values indicate the allocated bandwidth, in 1/1000ths of a gigabit/s
> >>>
> >>>e.g. The following for a PF with 4 VFs allocates ~20Mbits/ to VF 1,
> >>>    ~100Mbit/s to VF 2, and leave the other 2 VFs with no allocation.
> >>>
> >>>    echo "20 100 0 0" > /sys/class/net/eth3/device/bandwidth_allocation
> >>>
> >>>This interface is intended to allow testing of the hardware feature.
> >>>There are ongoing discussions about how to expose this feature
> >>>to user-space in a more generic way.
> >>>
> >>>Signed-off-by: Simon Horman <horms@verge.net.au>
> >>>
> >>Of the patches it looks like the only one that really has any issues
> >>is this one and it is mostly due to the sysfs implementation.  The
> >>others I would say can be applied and pushed up into the
> >>net-next-2.6 tree.
> >
> >Thanks, I suspected as much.
> >
> >>We're currently working on an iproute2 based solution for
> >>configuring VFs and can incorporate this functionality into it at
> >>some point in the future.
> >
> >Do you have any pointers to discussions relating to that interface.
> >Do you think it would be worth putting in the sysfs interface in the
> >mean-time, or would you rather wait?
> 
> I'm not the one working on the interface so I don't know much about
> it other than the fact it is being worked on.  Hopefully we should
> see something in regards to that soon though.

Great, I look forward to hearing something soon.

> If anything it might be of some use to split this up into 2 patches.
> One that contains the sysfs bits, and another for enabling the
> bandwidth control registers.  We won't be able to get the sysfs
> interface accepted upstream so there isn't much point in us keeping
> it around for any other purpose than testing to verify the registers
> work as you have described.

Understood with regards to the sysfs interface being umergable.
Do you think the non-sysfs portion would be acceptable even
though there would be no in-tree callers?