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[Xen-devel] XenLoop - Inter-VM Network Loopback

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] XenLoop - Inter-VM Network Loopback
From: "Kartik Gopalan" <kartik@xxxxxxxxxxxxxxxxx>
Date: Sat, 9 Feb 2008 21:07:42 -0500
Delivery-date: Sat, 09 Feb 2008 18:08:09 -0800
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We recently developed XenLoop -- a transparent inter-VM
network loopback mechanism. XenLoop allows unmodified
network applications to bypass the standard
network data path via Dom0 when talking with
other guest VMs on the same machine.

We'd very much like to hear usage feedback and
suggestions from others interested in this work.

XenLoop code and documentation is available here:

XenLoop differs from earlier approaches (such as
XenSockets, IVC, and XWay) as follows:
- No changes, such as recompiling or relinking,
  are needed to the user applications or libraries.
- XenLoop doesn't modify any part of the core kernel code
- XenLoop transparently adapts to migration without
  disrupting any ongoing network communication and
  without user or application intervention.
- Being implemented between the network and data-link
  layers (using netfilter hook), XenLoop can currently
  handle all IPv4 traffic, and likely others in near future.
- On the flip side, XenLoop presently incurs the TCP/IP
  protocol processing cost in each guest, which other
  approaches can avoid to obtain higher throughput
  while trading off some application-level or kernel-level

We still observe quite a decent improvement in
inter-VM communication performance on dual-core
machines when compared to the Dom0 data path -- up to
5X reduction in RTT and up to 6X increase in throughput.
We've tested XenLoop on Xen 3.1 and Linux 2.6.18.
Next steps are to try it on Xen 3.2 and to possibly
move traffic interception higher up the protocol stack.

Please contact Jian Wang (jianwang@xxxxxxxxxxxxxxxxx)
and Kartik Gopalan (kartik@xxxxxxxxxxxxxxxxx).

Kartik Gopalan
Assistant Professor, Computer Science
Thomas J. Watson School of Engineering and Applied Sciences
State University of New York at Binghamton

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