Bug 473114

Summary: RHEL 5.3: allow virtio_net support larger MTU sizes
Product: Red Hat Enterprise Linux 5 Reporter: Mark McLoughlin <markmc>
Component: kernelAssignee: Mark McLoughlin <markmc>
Status: CLOSED ERRATA QA Contact: Martin Jenner <mjenner>
Severity: high Docs Contact:
Priority: high    
Version: 5.3CC: kernel-mgr, mgahagan, mwagner, ovirt-maint, syeghiay, xen-maint
Target Milestone: rc   
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2009-01-20 19:58:56 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Attachments:
Description Flags
virtio_net-jumbo-frame-support.patch none

Description Mark McLoughlin 2008-11-26 15:55:00 UTC 
Currently, the virtio_net driver doesn't support setting it's MTU size to more
than 1500 bytes:

  $> ip link set eth0 mtu 9000
  SIOCSIFMTU: Invalid argument

In order to gain the performance improvement resulting from less packet
overhead, it's quite common for customers to configure their network so that
the entire path between two nodes support jumbo frames (i.e. frame size of 9000
bytes).

Since virtio_net doesn't support this, it's impossible to obtain this benefit with
KVM/virtio guests.

The patch to implement this support is quite trivial and has been just submitted upstream here:

  http://kerneltrap.org/mailarchive/linux-netdev/2008/11/26/4239974
Comment 2 Mark McLoughlin 2008-11-26 17:46:23 UTC 
Created attachment 324771 [details]
virtio_net-jumbo-frame-support.patch
Comment 5 Don Zickus 2008-12-09 21:05:39 UTC 
in kernel-2.6.18-126.el5
You can download this test kernel from http://people.redhat.com/dzickus/el5
Comment 8 errata-xmlrpc 2009-01-20 19:58:56 UTC 
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2009-0225.html