Mellanox Check For Write Combining Support
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux-azure (Ubuntu) |
Fix Released
|
Undecided
|
Marcelo Cerri | ||
Bionic |
Invalid
|
Undecided
|
Unassigned | ||
Focal |
Fix Released
|
Undecided
|
Unassigned | ||
linux-azure-4.15 (Ubuntu) |
New
|
Undecided
|
Unassigned | ||
Bionic |
Fix Released
|
Undecided
|
Unassigned | ||
Focal |
Invalid
|
Undecided
|
Unassigned |
Bug Description
[Impact]
Microsoft and Mellanox would like to request the following two commits in the releases that run on Azure:
3f89b01f4bba IB/mlx5: Align usage of QP1 create flags with rest of mlx5 defines
11f552e21755 IB/mlx5: Test write combining support
These commits landed in mainline as of v5.5-rc1.
These commits will improved network performance of RDMA out of the VF when WC can be used. The highest benefit is to RDMA and DPDK, but UCX should also see improved latency.
The Mellanox driver uses WC to optimize posting work to the HCA, and getting this wrong in either direction can cause a significant performance loss. These patches prevent the possible performance loss.
[Test Case]
Simply measure the network performance with the patches applied to check if there was some gain.
[Regression Potential]
It affects mainly the mlx5 driver and IB, while many of the instances do not make use of those, they are used by the high performance users.
CVE References
description: | updated |
Changed in linux-azure (Ubuntu Focal): | |
status: | In Progress → Fix Committed |
Changed in linux-azure-4.15 (Ubuntu Bionic): | |
status: | In Progress → Fix Committed |
Patches were submitted to mailing review: https:/ /lists. ubuntu. com/archives/ kernel- team/2020- August/ 112961. html