Seeking a path to zero-copy paravirtualised networking in the Linux kernel

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One Line Summary

How can we reintroduce the zero-copy behaviour that was removed as
part of the process of upstreaming Xen's netback driver


The Xen paravirtualised network protocol includes the possibility for
the backend domain to map pages belonging to the peer domain directly
in order to avoid a copy on the guest transmit path (i.e. the receive
path from the backends point of view). However in order to do this the
backend driver needs greater insight (and control over) the life-cycle
of pages in an skb’s paged fragment list than is currently available
from the Linux networking stack, since it is necessary to know when
the page is really finished with, even in the face of cloning and
other reference counting activities.

In this talk and the following discussion I would like to explore the
issues with the previous (out of tree) solution and investigate
potential paths to recreating this behaviour as well as consider other
potential users who may benefit from changes of this nature.


networking, xen

Presentation Materials



  • Ian Campbell

    Citrix Systems


    Ian Campbell has been involved with the Xen project since joining XenSource in 2005. Today he is a Principal Software Engineer at Citrix Systems, Inc ( working on Xen where his interests include Linux on Xen, paravirtualised networking and toolstack issues. Prior to Citrix (and XenSource) he worked on embedded Linux systems at Arcom Control Systems.