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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.
+![iops_500-1M](/uploads/f63ecbfdb13adc87bd4524f5298a224c/iops_500-1M.png)
+
+
+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
+```
+![iops_500-2M](/uploads/0a384fd9f026943e5e40af1c4b5d6dcd/iops_500-2M.png)
+
+
+If I set the qemu x-iops-total value to 1500 and the fio --bs value to 2M test again, I get 500Mib throughput.
+
+![iops_1500-2M](/uploads/f31eb8213d034d612e915e355b52a324/iops_1500-2M.png)
+
+
+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"