Re: [Questions] non-shared disk migration: jobs abort and bandwidth

On Wed, Jun 08, 2022 at 17:32:57 +0800, Han Han wrote: > Hi developers, > Recently, I am researching migration with non-share disk(flags > VIR_MIGRATE_NON_SHARED_DISK and VIR_MIGRATE_NON_SHARED_INC). > As we know, the non-shared disk migration could have block jobs to copy the > disk image from the src host to the dst host. So here are my questions for > non-shared disk migration: > q1. For the API virDomainMigrate3 with the bandwidth param, could it set > the bandwidth of block jobs? > q2. For the API virDomainMigrateSetMaxSpeed, could it set the bandwidth of > block jobs? > q3. For the domain job abort API virDomainAbortJob, could it stop the block > job of non-shared disk migration? > q4. For the block job bandwidth API virDomainBlockJobSetSpeed, could it set > the block job of non-shared disk migration? > q5. For the block job abort API virDomainBlockJobAbort, could it stop the > block job of non-shared disk migration? > > > > Then I got the test results of libvirt-8.4.0-1.el9.x86_64 > qemu-kvm-7.0.0-4.el9.x86_64: > q1: The bandwidth limit of virDomainMigrate3 is effective to the blockjob: > ➜ ~ virsh migrate OVMF qemu+ssh://root@hhan-rhel9--1/system --live --p2p > --tls --tls-destination hhan-rhel9--1 --copy-storage-all --disks-uri > tcp://hhan-rhel9--1:49156 --bandwidth 2 > ➜ ~ virsh blockjob OVMF vda > Block Copy: [ 0 %] Bandwidth limit: 2097152 bytes/s (2.000 MiB/s) This is expected and desired. > q2: The virDomainMigrateSetMaxSpeed doesn't change the the bandwidth of > block jobs. > ➜ ~ virsh migrate-setspeed OVMF 8 > > ➜ ~ virsh blockjob OVMF vda > Block Copy: [ 9 %] Bandwidth limit: 2097152 bytes/s (2.000 MiB/s) This is a bug though, setting the migration speed should, based on the fact that we want to use the global migration speed flag for disks too , apply also to the disk migration streams.

> q3: The virDomainAbortJob could stop a block job of non-shared disk > migration > ➜ ~ virsh migrate OVMF qemu+ssh://root@hhan-rhel9--1/system --live --p2p > --tls --tls-destination hhan-rhel9--1 --copy-storage-all --disks-uri > tcp://hhan-rhel9--1:49156 --bandwidth 2 > Then start a virsh event on another terminal: > ➜ ~ virsh event --loop --all > > Abort the domain job: > ➜ ~ virsh domjobabort OVMF > > The error "error: operation aborted: migration out: canceled by client" > appears at the terminal of "virsh migrate" > The terminal of "virsh event" shows the block job has been failed: > event 'block-job' for domain 'OVMF': Block Copy for > /var/lib/libvirt/images/OVMF.qcow2 failed > event 'block-job-2' for domain 'OVMF': Block Copy for vda failed This is again expected, the blockjobs are started by the migration thus when you cancel the migration we also need to cancel the blockjobs. > q4: The block job bandwidth of non-shared disk migration cannot be set by > virDomainBlockJobSetSpeed: > ➜ ~ virsh blockjob OVMF vda --bandwidth 10 > error: Timed out during operation: cannot acquire state change lock (held > by monitor=remoteDispatchDomainMigratePerform3Params) This is okay, but we could take it a sa feature request to allow tuning of the individual blockjobs.

> q5: The block job of non-shared disk migration cannot be aborted by > virDomainBlockJobAbort: > ➜ ~ virsh blockjob OVMF vda --abort > error: Timed out during operation: cannot acquire state change lock (held > by monitor=remoteDispatchDomainMigratePerform3Params) This is expected. Same as above, we dodn't want to allow users to control this. In contrast to 'q4' I'd refuse a RFE to allow cancelling of individual jobs. > Are the results above expected? > Here are my personal thoughts: > For the bandwidth in q1 and q2, they are commented as migration bandwidth( > https://gitlab.com/libvirt/libvirt/-/blob/master/include/libvirt/libvirt-... > , > https://gitlab.com/libvirt/libvirt/-/blob/master/src/libvirt-domain.c#L9696 > ), but one works for block jobs while one doesn't. So we should make the > comment clear whether they are the bandwidth of VM migration or the > bandwidth of migration with blockjobs. What's more, add a flag to > virDomainMigrateMaxSpeedFlags to support set bandwidth to the blockjobs in > migration. > For q4 and q5, if we will not support to change the block job of non-shared > disk migration by blockjob APIs, we should note that in the migration doc > or the block job doc, to present the difference between this type of block > job and the others.