[linux-azure] Storage performance drop on RAID
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
linux-azure (Ubuntu) |
Fix Released
|
Undecided
|
Unassigned | ||
Xenial |
Fix Released
|
Undecided
|
Unassigned |
Bug Description
In Azure, FIO 4k tests are showing performance drops on latest proposed 4.15.0 linux-azure kernels - from 52K IOPS to ~38K IOPS (max value reached on both sequential and random read tests).
The setup used is 12 disks in RAID0.
The affected kernels are:
Ubuntu 14.04 + 4.15.0-1043
Ubuntu 16.04 + 4.15.0-1044
Previous kernel versions had reached max IOPS, ~52K IOPS on both read tests (e.g. 16.04 + 4.15.0-1043 kernel). Right now, it seems like the issue is in the diff from 1043 kernel on trusty vs 1044 kernel on xenial.
The 52K IOPS is expected at qdepth=256. The repro cmd (as ran by the automation) is this:
fio --size=1023G --direct=1 --ioengine=libaio --filename=/dev/md0 --overwrite=1 --readwrite=
Changed in linux-azure (Ubuntu Xenial): | |
status: | New → Fix Committed |
tags: | added: patch |
The following commit was added in bug fa55b5d226dd.
7ac257b862f2c (“blk-mq: remove the request_list usage”)
This commit cleans up unused code in block-mq (mq uses pre-allocated tags to allocate request, not request_list as it's used only in legacy queue).
A test kernel with a revert of this commit would prove if it is the cause of this regression.