[Engine-devel] Updates in VdsUpdateRuntimeInfo

[Liran Zelkha]

Hi all,

Current status of VdsUpdateRuntimeInfo (please note - patch is not yet committed).
Initial UpdateRuntimeInfo performance wasted roughly 57% of CPU time on DB activity. Of that, about 25% of CPU time wasted on update behavior. 
After modification (moving updates to batch update) UpdateRuntimeInfo performance wasted roughly 40% of CPU time on DB activity. And only 12% of that was wasted on update behavior.

My next task is to try and optimize the rest of overall database performance.


----- Original Message -----
From: "Liran Zelkha" <liran.zelkha at gmail.com>
To: "Barak Azulay" <bazulay at redhat.com>
Cc: "engine-devel" <engine-devel at ovirt.org>
Sent: Wednesday, June 12, 2013 12:35:03 PM
Subject: Re: [Engine-devel] Updates in VdsUpdateRuntimeInfo

Hi guys,

I'm working hard on this. I'll send summary mail and findings later today. 

On Jun 12, 2013, at 10:45 AM, Barak Azulay wrote:

> 
> 
> ----- 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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>> 
>> 
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