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id = 1718
title = "Strange throttle-group test results"
state = "opened"
created_at = "2023-06-20T08:54:56.813Z"
closed_at = "n/a"
labels = []
url = "https://gitlab.com/qemu-project/qemu/-/issues/1718"
host-os = "Ubuntu 22.04.1 LTS"
host-arch = "x86"
qemu-version = "7.2.0"
guest-os = "CentOS Linux release 7.9"
guest-arch = "x86"
description = """I have a question about throttle-group test results.
I did a test to limit IO by applying THROTTLE-GROUP and the expected result is not what I expected
The setup environment looks like this throttle-group to x-iops-total=500, x-bps-total=524288000 and throttling vdb, benchmarked with fio command
```
# mount -t xfs /dev/vdb1 /mnt/disk
# fio --direct=1 --bs=1M --iodepth=128 --rw=read --size=1G --numjobs=1 --runtime=600 --time_based --name=/mnt/disk/fio-file --ioengine=libaio --output=/mnt/disk/read-1M
```
When I test with a --bs value of 1M, I get 500Mib throughput.
When I test with a --bs value of 2m, I don't get 500Mibs but 332Mibs throughput.
```
fio --direct=1 --bs=2M --iodepth=128 --rw=read --size=1G --numjobs=1 --runtime=600 --time_based --name=/mnt/disk/fio-file --ioengine=libaio --output=/mnt/disk/read-2M
```
If I set the qemu x-iops-total value to 1500 and the fio --bs value to 2M test again, I get 500Mib throughput.
To summarize, here is the Test result.
| fio bs | qemu x-iops-total | qemu x-bps-total | Result iops |Result throughput
| ------ | ------ |------ |------ |------ |
| 2M | 1500 | 524288000 | 250 | 500 |
| **2M** |**500** | **524288000** | **166** | **332** |
| 1M | 1500 | 524288000 | 500 | 500 |
| 1M | 500. | 524288000 | 500 | 500 |
When the --bs value is 2M and the x-iops-total value is 500, the throughput should be 500, but it is not, so I don't know what the problem is.
If there is anything I missed, please let me know."""
reproduce = """1. Apply throttle-group to vdb and start the VM
2. mount vdb1
3. test fio"""
additional = "n/a"
|