[Engine-devel] Updates in VdsUpdateRuntimeInfo

[Barak Azulay]

----- Original Message -----
> From: "Itamar Heim" <iheim at redhat.com>
> To: "Barak Azulay" <bazulay at redhat.com>
> Cc: "engine-devel" <engine-devel at ovirt.org>
> Sent: Wednesday, June 12, 2013 10:09:09 AM
> Subject: Re: [Engine-devel] Updates in VdsUpdateRuntimeInfo
> 
> On 06/12/2013 09:41 AM, Barak Azulay wrote:
> >
> >
> > ----- Original Message -----
> >> From: "Itamar Heim" <iheim at redhat.com>
> >> To: "Liran Zelkha" <lzelkha at redhat.com>
> >> Cc: "engine-devel" <engine-devel at ovirt.org>
> >> Sent: Tuesday, June 11, 2013 4:00:21 PM
> >> Subject: Re: [Engine-devel] Updates in VdsUpdateRuntimeInfo
> >>
> >> On 06/11/2013 03:26 PM, Liran Zelkha wrote:
> >>> Hi all,
> >>>
> >>> I'm checking performance for VdsUpdateRunTimeInfo.
> >>> Naturally, much of the performance surrounds database activity
> >>> (getVmsRunningOnVds queries, updateDeviceRuntimeInfo, updateVmDynamic)
> >>>
> >>> Few questions:
> >>> 1. I have implemented batch updates for procedure
> >>> UpdateVmDeviceRuntimeInfo
> >>> for improved performance.
> >>> 2. Seems like the only parameters UpdateVmDeviceRuntimeInfo is getting
> >>> are
> >>> vm_id,vm_device_id,address and alias. Are those rapidly changing, or will
> >>> it be beneficial to implement caching on those updates (to ensure
> >>> not-required updates do not travel to the database).
> >>
> >> slowly changing, but how will you cover all flows changing these devices
> >> to invalidate the cache (iiuc, this table is modified by engine when
> >> adding devices to a VM as well?)
> >
> >
> > I don't think that in the device run time info we need to invalidate once
> > we add a device.
> > This is a specific case where we actually get the information from the VDSM
> > (addresses are received from libvirt)
> > The commands IIRC are first send to VDSM and than update the runtime info
> > only on changed info (we can also hash it),
> > It may put the placeholder in the DB first but it still relies on the data
> > received from VDSM.
> 
> if this table is only updated from vdsm to save it, i agree.
> but isn't the engine also manipulating it?
> wasn't there a request to be able to maybe edit the addresses some day?

Even if there was such a request, we still update when we receive the info from libvirt.

Anyway there are obviously a few improvements to be done before caching.
- update only when info received from VDSM change (need to verify it is the practice here)
- do batch update for the new updated data received.
- do the hashing (of vm device runtime info) on VDSM for the data , and update only when hash changes
- caching ...

Barak
 


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