[libvirt] [RFC PATCH 00/12] Add block write threshold event
Eric Blake
eblake at redhat.com
Thu Feb 23 19:50:03 UTC 2017
On 02/23/2017 01:21 PM, Peter Krempa wrote:
> Since I'm a procrastinator and I wanted to do this after full node-name support
> is added I'm kind of late for this release here. Since oVirt is asking for this
> feature for a very long time I would like to deliver it ASAP though.
Thanks for picking up on this. I tried once a long time ago:
https://www.redhat.com/archives/libvir-list/2015-June/msg01111.html
and got stalled on node name weirdness, so it never went in.
>
> This series adds a event which is fired once a guest writes beyond a configured
> offset in the backing file. The threshold offset is configurable via a new API.
>
> This series is in RFC state since I did not manage to polish few details mostly
> connected to node names:
>
> - currently only the top level image can be selected
> - some blockjobs may clear the remembered node names and thus break this
> ( re-detection of the backing chain needs to be connected with node name
> detection )
> - the node name detection code is VERY crude
Indeed, that's where I got stalled, but I think you may already be
further along than my attempt. (It may also be that the QMP side from
qemu is easier to use now than when I first tried)
> - I'm not sure how well it plays with qcow images, since I select only the top
> level node (qcow protocol) rather than the file backing it
That may be a deal-breaker - my recollection is that you HAVE to use the
node-name of the file backing the qcow2 to get the useful threshold, and
not the node-name of the qcow2 protocol.
> - the documentation probably sucks since I did not proof-read
>
> Any feedback is welcome.
>
> Peter Krempa (12):
> util: storage: Split out useful bits of virStorageFileParseChainIndex
> util: storage: Add preliminary storage for node names into
> virStorageSource
> lib: Introduce event for tracking disk backing file write threshold
> qemu: monitor: Add support for BLOCK_WRITE_THRESHOLD event
> qemu: domain: Add helper to lookup disk by node name
> qemu: domain: Add helper to generate indexed backing store names
> qemu: process: Wire up firing of the
> VIR_DOMAIN_EVENT_ID_BLOCK_THRESHOLD event
> lib: Add API for setting the threshold size for
> VIR_DOMAIN_EVENT_ID_BLOCK_THRESHOLD
> virsh: Implement 'blockthreshold' command to call
> virDomainSetBlockThreshold
> qemu: domain: Add helper to look up disk soruce by the backing store
> string
> qemu: implement qemuDomainSetBlockThreshold
> qemu: WIP: lookup nodenames
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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