Re: [libvirt] [PATCHv5 12/23] blockjob: relax block job behavior when setting speed up front

On Mon, Apr 16, 2012 at 23:06:03 -0600, Eric Blake wrote: > In qemu, it is possible to call 'migrate_set_speed' prior to > 'migrate', and therefore ensure a constant throttling through the > entire migration. However, this is not possible with > 'block-job-set-speed', which fails if a job is not already active. > This means that you can't detect a device that doesn't support > throttling until after you have already started a block job and > let an unknown amount of unthrottled data through. Aborting the > job upon failure to set the speed seems a bit harsh, since it > would have been nicer to prevent the job from starting in the > first place, rather than letting an unknown amount of data be > processed before detecting the speed failure. So I propose > relaxing the documentation, and explicitly mentioning that setting > the speed is a best-effort attempt that might be ignored. On the > other hand, I've also requested that qemu consider adding an > optional parameter to allow setting the speed at the creation of a > block job. > > * src/libvirt.c (virDomainBlockPull, virDomainBlockRebase): Update > the documentation. > * src/qemu/qemu_driver.c (qemuDomainBlockJobImpl) > (qemuDomainBlockCopy): Log but don't fail when speed change fails. > --- > > v5: new patch; see also this qemu request: > https://lists.gnu.org/archive/html/qemu-devel/2012-04/msg02185.html > > src/libvirt.c | 12 ++++++++++-- > src/qemu/qemu_driver.c | 18 ++++++++++++------ > 2 files changed, 22 insertions(+), 8 deletions(-) OK