Re: [libvirt] [RFC][scale] new API for querying domains stats
----- Original Message -----
From: "Richard W.M. Jones" <rjones(a)redhat.com>
To: "Li Wei" <lw(a)cn.fujitsu.com>
Cc: "Francesco Romani" <fromani(a)redhat.com>, libvir-list(a)redhat.com
Sent: Tuesday, August 12, 2014 11:04:05 AM
Subject: Re: [libvirt] [RFC][scale] new API for querying domains stats
[...]
> > Is it possible to design an API that can work across all
domains
> > in a single call?
>
> How about the following API:
>
> int virConnectGetAllBlockStats(virConnectPtr conn,
> virDomainPtr domain,
> virDomainBlockBulkStatsPtr *stats,
> unsigned int flags);
> @conn: pointer to libvirt connection
> @domain: pointer to the domain to be queried, NULL for all domains
> @stats: array of virDomainBlockBulkStats struct(see below) to be populated
> @flags: filter flags
> Return the number of virDomainBlockBulkStats populated.
>
> where virDomainBlockBulkStats defined as:
>
> struct _virDomainBlockBulkStats {
> virDomainPtr domain; /* domain the block stats belongs to */
> virTypedParameterPtr params; /* params to store block stats */
> unsigned int nparams; /* how many params used for each block stats */
> unsigned int ndisks; /* how many block stats in this domain */
> };
Works for me.
Same here.
oVirt, more specifically VDSM, needs to check all the stats of all
the domains on a given host at once, so this API should fit the task.
Since VDSM takes ownership (read: keep track and control) of all the VMs,
the filtering capability of this new API should be good enough.
+++
It would be nice, but less important, to be able to somehow reuse the
`stats' argument.
What I'm looking here is a way to avoid to allocate/deallocate every time
all the needed structure before and after each call.
I'm saying so because is a pretty common scenario for a VM (at least in
the cases I'm aware of) to have the same number of disks during all its life.
But I believe this is an optimization which can be added later.
Thanks,
--
Francesco Romani
RedHat Engineering Virtualization R & D
Phone: 8261328
IRC: fromani