Azure: swiotlb patch needed for CVM
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux-azure (Ubuntu) |
Invalid
|
Undecided
|
Unassigned | ||
Jammy |
Fix Released
|
Medium
|
Tim Gardner |
Bug Description
SRU Justification
[Impact]
[Azure][CVM] Include the swiotlb patch to increase the disk/network performance
Description
As we discussed, there will be new CVM-supporting linux-azure kernels that're based on v5.13 and v5.15. Here I'm requesting the below patch to be included into the two kernels because it can significantly improve the disk/network performance:
swiotlb: Split up single swiotlb lock: https:/
We have tested the patch with the upstream 5.16-rc8.
BTW, the patch is unlikely to be in the mainline kernel, as the community is trying to resolve the lock contention issue in the swiotlb code using a different per-device per-queue implementation, which would need quite some time to be finalized -- before that happens, we need this out-of-tree patch to achieve good disk/network performance for CVM GA on Azure.
(BTW, the v5.4-based linux-azure-cvm kernel does not need the patch, because it uses a private bounce buffer implementation: drivers/
[Test Case]
[Microsoft tested]
I tried the April-27 amd64 test kernel and it worked great for me:
1. The test kernels booted up successfully with 256 virtual CPUs + 100 GB memory.
2. The kernel worked when I changed the MTU of the NetVSC NIC.
3. The Hyper-V HeartBeat/
4. I did some quick disk I/O and network stress tests and found no issue.
When I did the above tests, I changed the low MMIO size to 3GB (which is the setting for a VM on Azure today) by "set-vm decui-u2004-cvm -LowMemoryMappe
Our test team will do more testing, including performance test. We expect the performance of this v5.15 test kernel should be on par with the v5.4 linux-azure-cvm kernel.
[Where things could go wrong]
Networking could fail or continue to suffer from poor performance.
[Other Info]
SF: #00332721
CVE References
affects: | linux (Ubuntu) → linux-azure (Ubuntu) |
description: | updated |
Changed in linux-azure (Ubuntu Jammy): | |
assignee: | nobody → Tim Gardner (timg-tpi) |
importance: | Undecided → Medium |
status: | New → In Progress |
Changed in linux-azure (Ubuntu): | |
status: | New → Invalid |
Changed in linux-azure (Ubuntu Jammy): | |
status: | In Progress → Fix Committed |
This bug is awaiting verification that the linux-azure/ 5.15.0- 1006.7 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- needed- jammy' to 'verification- done-jammy' . If the problem still exists, change the tag 'verification- needed- jammy' to 'verification- failed- jammy'.
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:/ /wiki.ubuntu. com/Testing/ EnableProposed for documentation how to enable and use -proposed. Thank you!