Re: [PATCH RFC 00/12] Support throttle block filters

From: Chun Feng Wu <wucf(a)linux.ibm.com&gt; Hi, I am thinking to leverage "throttle block filter" in QEMU to support more flexible I/O limits(e.g. tiered I/O groups), one sample provided by QEMU doc is: https://github.com/qemu/qemu/blob/master/docs/throttle.txt "For example, let's say that we have three different drives and we want to set I/O limits for each one of them and an additional set of limits for the combined I/O of all three drives." The implementation idea is to - Define throttle groups(limit) in domain - Define throttle filter to reference throttle group within disk - Within domain disk, throttle filters references multiple throttle groups to form filter chain to apply multiple limits in QEMU like above sample - Add new virsh cmds for throttle group management: throttlegroupset Add or update a throttling group. throttlegroupdel Delete a throttling group. throttlegroupinfo Get a throttling group. throttlegrouplist list all domain throttlegroups - Update "attach-disk" to add one more option "--throttle-groups" to apply throttle filters e.g. "virsh attach-disk $VM_ID ${DISK_PATH}/vm1_disk_2.qcow2 vdd --driver qemu --subdriver qcow2 --targetbus virtio --throttle-groups limit2,limit012" - I chose above semantics as I felt they're appropriate, if there are better ones please kindly suggest. This patchset includes: - Throttle group and throttle filter definition in patch 1 - New QMP processing to update and get throttle group in patch 2 - New API definition and implementation in patch 3 - Hotplug and qemuProcessLaunch flow implemenation in patch 4, 5 - Domain XML schema and doc(formatdomain.rst) change in patch 6 - Tests in patch 7, 8 - Virsh cmd implementation in patch 9 - Other enhencement/verification implementation in patch 10, 11, 12

Any comments/suggestions will be appriciated!