Bug 713337
| Summary: | backport checksum optimization for virtio_net | ||||||
|---|---|---|---|---|---|---|---|
| Product: | Red Hat Enterprise Linux 6 | Reporter: | jason wang <jasowang> | ||||
| Component: | kernel | Assignee: | jason wang <jasowang> | ||||
| Status: | CLOSED ERRATA | QA Contact: | Red Hat Kernel QE team <kernel-qe> | ||||
| Severity: | unspecified | Docs Contact: | |||||
| Priority: | medium | ||||||
| Version: | 6.2 | CC: | akong, juzhang, mst, rhod, tburke, vrozenfe, wquan, yvugenfi | ||||
| Target Milestone: | rc | ||||||
| Target Release: | --- | ||||||
| Hardware: | Unspecified | ||||||
| OS: | Unspecified | ||||||
| Whiteboard: | developer-ack-6.2 | ||||||
| Fixed In Version: | kernel-2.6.32-176.el6 | Doc Type: | Bug Fix | ||||
| Doc Text: | Story Points: | --- | |||||
| Clone Of: | |||||||
| : | 713643 (view as bug list) | Environment: | |||||
| Last Closed: | 2011-12-06 13:41:15 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: | |||||||
| Bug Depends On: | |||||||
| Bug Blocks: | 713643 | ||||||
| Attachments: |
|
||||||
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. 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. *** Bug 713615 has been marked as a duplicate of this bug. *** Patch(es) available on kernel-2.6.32-176.el6 Created attachment 527175 [details]
summary-1vm-external-to0guest-gro-off test result
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 ~ 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. (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. 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 |
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: