Thanks for your info! Currently, the iotune in libvirt’s xml indeed works well, BTW, is there any plan for such “re-engineering”?

From: Peter Krempa <pkrempa@redhat.com>
Date: Monday, October 16, 2023 at 21:53
To: Chun Feng Wu <wucf@cn.ibm.com>
Cc: libvir-list@redhat.com <libvir-list@redhat.com>
Subject: [EXTERNAL] Re: [libvirt] [PATCHv2 37/62] qemu: process: Setup disk io throttling for -blockdev

On Mon, Oct 16, 2023 at 13:36:42 +0000, Chun Feng Wu wrote:
> Does this libvirt throttling support “chained throttle filters” for single disk described in QEMU doc: https://github.com/qemu/qemu/blob/master/docs/throttle.txt  (“The 'throttle' block filter”)

No, libvirt currently still uses the older approach by using
'block_set_io_throttle' QMP command. This was used at the beginning
because the 'throttle' layer was not yet ready at the point when libvirt
adopted -blockdev.

It is sufficient for the throttling options that are currently
configurable via libvirt's XML.

Note that to use the full potential of the throttle groups and
hierarchical throttling will require significant re-engineering of the
XML configuration of throttling.