Allow drivers to use Relaxed Ordering on capable root ports
| Affects | Status | Importance | Assigned to | Milestone | |
|---|---|---|---|---|---|
| linux (Ubuntu) |
Fix Released
|
Medium
|
dann frazier | ||
| Zesty |
Won't Fix
|
Medium
|
dann frazier | ||
| Artful |
Fix Released
|
Medium
|
dann frazier | ||
Bug Description
[Impact]
A signficant performance gain can be achieved with the iperf benchmark by allowing the ixgbe driver to take advantage of PCIe Relaxed Ordering, as observed on the HiSilicon D05 system.
[Test Case]
Setup two servers with dual-port PCIe ixgbe cards, connected back-to-back.
= server =
taskset -c 0-15 iperf -s -B 192.168.80.11 &
taskset -c 16-31 iperf -s -B 192.168.90.11 &
= client =
taskset -c 0-15 iperf -c 192.168.80.11 -i 3 -t 600 -P 8 &
taskset -c 16-31 iperf -c 192.168.90.11 -i 3 -t 600 -P 8 &
Without these patches, we observe an aggregate performance of 8.54 Gbit/sec. With these patches, we observe an aggregate performance of 18.82 Gbit/sec.
[Regression Risk]
The following risk assessment applies to both artful and zesty - but note that the bulk of these changes are *already in artful*. The proposed SRU for artful would just allow an additional driver to take advantage of it. For zesty, an SRU would need to both introduce this feature and enable it for both the cxgb4 and ixgbe drivers.
The patchset is careful to only enable Relaxed Ordering if advertised up through the root port. However, it is possible that enabling RO on hardware that supports it could actually regress performance, or that there is hw out there that advertises RO, but has bugs in the implementation. The patch series includes quirks for HW where RO is advertised but known to have issues[*] - but this list maybe incomplete. This would only impact devices w/ drivers that take advantage of RO - currently cxgb4 and (not yet upstream) ixgbe.
Also, there is a possibility of a crash caused by a coding error. One such issue has already been found and fixed upstream [**], and is part of this series.
The risk of both of these regressions is reduced by the fact that this code is upstream, and has therefore gotten a lot more testing that has not resulted in regressions reports.
[*]
commit 077fa19c5dfa06a
Author: dingtianhong <email address hidden>
Date: Tue Aug 15 11:23:25 2017 +0800
PCI: Disable Relaxed Ordering Attributes for AMD A110
commit 87e09cdec4dae08
Author: dingtianhong <email address hidden>
Date: Tue Aug 15 11:23:24 2017 +0800
PCI: Disable Relaxed Ordering for some Intel processors
[**]
commit 0e405232871d67b
Author: dingtianhong <email address hidden>
Date: Tue Aug 15 23:24:48 2017 +0800
PCI: fix oops when try to find Root Port for a PCI device
CVE References
| Changed in linux (Ubuntu Zesty): | |
| status: | New → Confirmed |
| assignee: | nobody → dann frazier (dannf) |
| description: | updated |
| Changed in linux (Ubuntu): | |
| status: | Fix Released → Confirmed |
| summary: |
- PCIe: Allow drivers to use Relaxed Ordering on capable root ports + ixgbe/PCIe: Allow drivers to use Relaxed Ordering on capable root ports |
| Changed in linux (Ubuntu): | |
| status: | Confirmed → In Progress |
| Changed in linux (Ubuntu Artful): | |
| status: | New → In Progress |
| assignee: | nobody → dann frazier (dannf) |
| Changed in linux (Ubuntu): | |
| assignee: | nobody → dann frazier (dannf) |
| Changed in linux (Ubuntu Zesty): | |
| importance: | Undecided → Medium |
| Changed in linux (Ubuntu Artful): | |
| importance: | Undecided → Medium |
| description: | updated |
| description: | updated |
| description: | updated |
| description: | updated |
| Changed in linux (Ubuntu Zesty): | |
| status: | Confirmed → In Progress |
| summary: |
- ixgbe/PCIe: Allow drivers to use Relaxed Ordering on capable root ports + Allow drivers to use Relaxed Ordering on capable root ports |
| Changed in linux (Ubuntu Artful): | |
| status: | In Progress → Fix Committed |
| Khaled El Mously (kmously) wrote | #1 |
| tags: | added: verification-needed-artful |
| tags: |
added: verification-done-artful removed: verification-needed-artful |
| dann frazier (dannf) wrote | #2 |
| Changed in linux (Ubuntu Zesty): | |
| status: | In Progress → Won't Fix |
| Changed in linux (Ubuntu): | |
| status: | In Progress → Fix Committed |
| Launchpad Janitor (janitor) wrote | #3 |
| Changed in linux (Ubuntu Artful): | |
| status: | Fix Committed → Fix Released |
| Launchpad Janitor (janitor) wrote | #4 |
| Changed in linux (Ubuntu): | |
| status: | Fix Committed → Fix Released |
This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-
If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.
See https:/