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Bug 713337 - backport checksum optimization for virtio_net
Summary: backport checksum optimization for virtio_net
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: kernel
Version: 6.2
Hardware: Unspecified
OS: Unspecified
medium
unspecified
Target Milestone: rc
: ---
Assignee: jason wang
QA Contact: Red Hat Kernel QE team
URL:
Whiteboard: developer-ack-6.2
: 713615 (view as bug list)
Depends On:
Blocks: 713643
TreeView+ depends on / blocked
 
Reported: 2011-06-15 02:55 UTC by jason wang
Modified: 2013-01-09 23:57 UTC (History)
8 users (show)

Fixed In Version: kernel-2.6.32-176.el6
Doc Type: Bug Fix
Doc Text:
Clone Of:
: 713643 (view as bug list)
Environment:
Last Closed: 2011-12-06 13:41:15 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
summary-1vm-external-to0guest-gro-off test result (5.58 KB, application/octet-stream)
2011-10-10 07:44 UTC, Quan Wenli 		no flags Details
View All


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2011:1530 0 normal SHIPPED_LIVE Moderate: Red Hat Enterprise Linux 6 kernel security, bug fix and enhancement update 2011-12-06 01:45:35 UTC

Description jason wang 2011-06-15 02:55:37 UTC 
Description of problem:
   
There's no need for the guest to validate the checksum if it have been
validated by host nics. So this patch introduces a new flag -
VIRTIO_NET_HDR_F_DATA_VALID which is used to bypass the checksum
examing in guest. The backend (tap/macvtap) may set this flag when
met skbs with CHECKSUM_UNNECESSARY to save cpu utilization.
    
No feature negotiation is needed as old driver just ignore this flag.
    
Iperf shows 12%-30% performance improvement for UDP traffic. For TCP,
when gro is on no difference as it produces skb with partial
checksum. But when gro is disabled, 20% or even higher improvement
could be measured by netperf.


Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1.
2.
3.
  
Actual results:


Expected results:


Additional info:
Comment 2 Ronen Hod 2011-06-15 06:35:46 UTC 
Jason,
Did you do any sanity testing for Windows guests? If there are no problems, then surely this nice performance gain should be included it in 6.2.
Thanks, Ronen.
Comment 3 RHEL Program Management 2011-06-15 12:49:54 UTC 
This request was evaluated by Red Hat Product Management for inclusion
in a Red Hat Enterprise Linux maintenance release. Product Management has 
requested further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed 
products. This request is not yet committed for inclusion in an Update release.
Comment 5 jason wang 2011-06-16 03:23:09 UTC 
*** Bug 713615 has been marked as a duplicate of this bug. ***
Comment 7 Aristeu Rozanski 2011-08-02 13:58:01 UTC 
Patch(es) available on kernel-2.6.32-176.el6
Comment 10 Quan Wenli 2011-10-10 07:44:11 UTC 
Created attachment 527175 [details]
summary-1vm-external-to0guest-gro-off test result
Comment 11 Quan Wenli 2011-10-10 07:45:19 UTC 
As checksum only effect RX packages, so runnning netperf TCP_STREAM (vm acts as server) test in GRO OFF to verify it between kernel-175 and 176 with qemu kvm_0.12.1.2-2.183.
from posted result shows 12% avg improvement in sum normalize.
for detail infomation, please refer summary-1vm-external-to-guest-gro-off.out file.

So change it to verified. thanks ~
Comment 12 Yvugenfi@redhat.com 2011-10-14 14:25:32 UTC 
Can you describe test setup? 

I implemented this feature for Windows guest driver but I cannot test it as I don't see that we are getting VIRTIO_NET_HDR_F_DATA_VALID flag from the host.
Comment 13 jason wang 2011-10-17 02:13:31 UTC 
(In reply to comment #12)
> Can you describe test setup? 
> 
> I implemented this feature for Windows guest driver but I cannot test it as I
> don't see that we are getting VIRTIO_NET_HDR_F_DATA_VALID flag from the host.

Hello Yan:

GRO is normally enabled in host, so we can not see VIRITO_NET_HDR_F_DATA_VALID for tcp stream. You can test with udp or disable GRO in host.
Comment 14 errata-xmlrpc 2011-12-06 13:41:15 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2011-1530.html
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