On Wed, Jan 08, 2025 at 06:45:54PM +0900, Henry lol wrote: > I want to apply a throttle block filter using the QMP command, but > it doesn't seem to work as the I/O performance remains the same. > > Are there any additional steps I need to follow? > I predefined the throttle-group object and block device in the QEMU > parameters and then used the blockdev-add QMP command to apply the > filter, as described in the link > - https://github.com/qemu/qemu/blob/master/docs/throttle.txt#L315-L322 > > Additionally, I’ve confirmed that the filter works well when defined > in the QEMU -drive parameter instead of using the QMP command.
Can you summarize the commands that you are using? Simply adding the filter with 'blockdev-add' is not enough, that creates the backend (the "host" part, i.e. how the block device is actually emulated) but you also need a frontend (the device that the guest VM can see, i.e. a SCSI hard drive, an SD card, etc.). The -drive parameter creates both things (frontend and backend). See here: https://www.linux-kvm.org/images/3/34/Kvm-forum-2013-block-dev-configuration.pdf Berto
