Red Hat Bugzilla – Bug 565560
[5.6 FEAT] KVM network performance: Defer skb allocation in virtio-net
Last modified: 2013-03-09 22:14:30 EST
1. Feature Overview:
Feature Id: 
a. Name of Feature: [5.6 FEAT] KVM network performance: Defer skb allocation in virtio-net
b. Feature Description
vhost-net patchset : add tap and raw socket backend support to host kernel to improve network latency
udp fragmentation offload: improve throughput of guest-host/guest-guest by enabling UFO to
send/receive large UDP packets
virtio-net performance enhancement : avoid unnecessary skb allocs/frees for large packet in guest
receive path by deferring skb allocations
IGMP Snooping: to briding code to improve multicast performnace when using a
bridge to connect multiple guests.
2. Feature Details:
Sponsor: LTC Networking
Arch Specificity: both
Affects Kernel Modules: Yes
Delivery Mechanism: Direct from Community
Request Type: Package - Version Update
d. Upstream Acceptance: Accepted
Sponsor Priority P2
f. Severity: high
IBM Confidential: No
Code Contribution: IBM code
g. Component Version Target:
3. Business Case
The network performance for communication across VM to VM and host-VM must be
close to native perf. to migrate applications to KVM, be competitive with
industry virtualization solutions, and support efficient workloads even as a
large number of VMs supported per host.
4. Primary contact at Red Hat:
5. Primary contacts at Partner:
Project Management Contact:
Stephanie A. Glass, email@example.com
Sridhar Samudrala, firstname.lastname@example.org
Please attach patches backported and tested against the RHEL5.5 kernel. Thanks!
Created attachment 405403 [details]
This is the proposed backport patch
------- Comment on attachment From email@example.com 2010-04-08 16:37 EDT-------
Tests are still going on, with this patch the initial test local guest to host netperf result is from 6730.45 Gb/s to
8019.53 Gb/s same cpu utilization rate.
------- Comment From firstname.lastname@example.org 2010-04-09 03:44 EDT-------
The patch has been tested. However, this patch seems triggered an existing bug in virtio_ring.c when removing virtio_net module manually. I am not going to include the fix in this patch. I will file a bug separately.
Created attachment 405486 [details]
virtio skb optimization patchset
------- Comment on attachment From email@example.com 2010-04-09 04:13 EDT-------
This patch has been tested. It's ready for pick up.
------- Comment From firstname.lastname@example.org 2010-04-09 04:21 EDT-------
The update patch has all fixes so we don't need to submit another fix.
IBM is signed up to test and provide feedback.
Created attachment 449303 [details]
Attached patch backported to RHEL5.6 kernel
Created attachment 449308 [details]
Attached patch backported to RHEL5.6 kernel (v2)
Created attachment 449534 [details]
Working backport to RHEL5.6 kernel
Attached patch works against the latest RHEL5.6 kernel tested under heavy network load in a RHEL5.5 KVM.
Anthony posted this to rh-kernel mailing list
This enhancement request was evaluated by the full Red Hat Enterprise Linux
team for inclusion in a Red Hat Enterprise Linux minor release. As a
result of this evaluation, Red Hat has tentatively approved inclusion of
this feature in the next Red Hat Enterprise Linux Update minor release.
While it is a goal to include this enhancement in the next minor release
of Red Hat Enterprise Linux, the enhancement is not yet committed for
inclusion in the next minor release pending the next phase of actual
code integration and successful Red Hat and partner testing.
You can download this test kernel (or newer) from http://people.redhat.com/jwilson/el5
Detailed testing feedback is always welcomed.
~~ Attention Customers and Partners - RHEL 5.6 Public Beta is now available on RHN ~~
A fix for this 'OtherQA' BZ should be present and testable in the release.
If this Bugzilla is verified as resolved, please update the Verified field above with an appropriate value and include a summary of the testing executed and the results obtained.
If you encounter any issues or have questions while testing, please describe them and set this bug into NEED_INFO.
If you encounter new defects or have additional patches to request for inclusion, promptly escalate the new issues through your support representative.
Finally, future Beta kernels can be found here:
Note: Bugs with the 'OtherQA' keyword require Third-Party testing to confirm the request has been properly addressed. See: https://bugzilla.redhat.com/describekeywords.cgi#OtherQA ).
Reminder! There should be a fix present for this BZ in snapshot 3 -- unless otherwise noted in a previous comment.
Please test and update this BZ with test results as soon as possible.
------- Comment From email@example.com 2010-12-02 12:15 EDT-------
This feature has been passed netperf test for snapshot 2. What else should we do for snapshot 3?
@IBM, nothing. Thanks for the information. I'll mark this bug as verified by IBM. Thanks!
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.