Subject: Re: AF_PACKET mmap() v4...

From: Richard Cochran <[email-masked]>
Date: Thu, 5 Nov 2015 07:53:35 +0100

On Thu, Nov 05, 2015 at 12:04:14AM -0500, David Miller wrote:
> So I want everyone to think about whether there are any other changes
> we might want to make given that we have to make a v4 anyways.

One thing I would like to see is a field for a desired transmit time.
Time based scheduling is a new topic, never discussed on this list
before, afaict.  HW already supports this, for example, the Intel i210
card has a high priority queue where you can tell it a Tx time in
terms of the PTP clock.

This functionality is useful in industrial Ethernet protocols.  There
must be a dozen of these out there, and a new IEEE standard is in the
works by Time Sensitive Networking (TSN) group.

I haven't thought too much about how to implement this, but the
eventual goal would be a generic time based scheduler that either uses
special HW features or does best effort in SW.  User space would have
a socket option for desired Tx time, and this should also be available
over the mmap interface.

Thanks,
Richard