Re: [Engine-devel] Updates in VdsUpdateRuntimeInfo
----- Original Message -----
From: "Itamar Heim" <iheim(a)redhat.com>
To: "Barak Azulay" <bazulay(a)redhat.com>
Cc: "engine-devel" <engine-devel(a)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(a)redhat.com>
>> To: "Liran Zelkha" <lzelkha(a)redhat.com>
>> Cc: "engine-devel" <engine-devel(a)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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