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-----Original Message-----
From: Jay Pipes [mailto:jaypipes at gmail.com] 
Sent: 06 May 2014 18:44
To: openstack-dev at lists.openstack.org
Subject: Re: [openstack-dev] [nova] Question about addit log in nova-compute.log

On 05/06/2014 01:37 PM, Jiang, Yunhong wrote:
>> -----Original Message-----
>> From: Jay Pipes [mailto:jaypipes at gmail.com]
>> Sent: Monday, May 05, 2014 6:19 PM
>> To: openstack-dev at lists.openstack.org
>> Subject: Re: [openstack-dev] [nova] Question about addit log in 
>> nova-compute.log
>>
>> On 05/05/2014 04:19 PM, Jiang, Yunhong wrote:
>>>> -----Original Message-----
>>>> From: Jay Pipes [mailto:jaypipes at gmail.com]
>>>> Sent: Monday, May 05, 2014 9:50 AM
>>>> To: openstack-dev at lists.openstack.org
>>>> Subject: Re: [openstack-dev] [nova] Question about addit log in 
>>>> nova-compute.log
>>>>
>>>> On 05/04/2014 11:09 PM, Chen CH Ji wrote:
>>>>> Hi
>>>>>                   I saw in my compute.log has following logs which
>> looks
>>>>> to me strange at first, Free resource is negative make me confused
>> and I
>>>>> take a look at the existing code
>>>>>                   looks to me the logic is correct and calculation
>> doesn't
>>>>> have problem ,but the output 'Free' is confusing
>>>>>
>>>>>                   Is this on purpose or might need to be enhanced?
>>>>>
>>>>> 2014-05-05 10:51:33.732 4992 AUDIT
>> nova.compute.resource_tracker
>>>> [-]
>>>>> Free ram (MB): -1559
>>>>> 2014-05-05 10:51:33.732 4992 AUDIT
>> nova.compute.resource_tracker
>>>> [-]
>>>>> Free disk (GB): 29
>>>>> 2014-05-05 10:51:33.732 4992 AUDIT
>> nova.compute.resource_tracker
>>>> [-]
>>>>> Free VCPUS: -3
>>>>
>>>> Hi Kevin,
>>>>
>>>> I think changing "free" to "available" might make things a little 
>>>> more clear. In the above case, it may be that your compute worker 
>>>> has both CPU and RAM overcommit enabled.
>>>>
>>>> Best,
>>>> -jay
>>>
>>> HI, Jay,
>>> 	I don't think change 'free' to 'available' will make it clearer.
>>> 	IMHO, the calculation of the 'free' is bogus. When report the 
>>> status in
>> the periodic task, the resource tracker has no idea of the 
>> over-commit ration at all, thus it simply subtract the total RAM 
>> number assigned to instances from the RAM number provided by 
>> hypervisor w/o considering the over-commitment at all. So this number really have meaningless.
>>
>> Agreed that in it's current state, it's meaningless. But... that 
>> said, the numbers *could* be used to show oversubscription 
>> percentage, and you don't need to know the max overcommit ratio in 
>> order to calculate that with the numbers already known.
>
> I don't think user can use these number to calculate the 'available'. User has to know the max overcommit ratio to know the 'available'. Also, it's really ironic to provide some meaningless information and have the user to calculate to get meaningful.
>
> This is related to https://bugs.launchpad.net/nova/+bug/1300775 . I think it will be better if we can have the resource tracker to knows about the ratio.

Sorry, you misunderstood me... I was referring to the resource tracker above, not a regular user. The resource tracker already knows the total amount of physical resources available on each compute node, and it knows the resource usage reported by each compute node. Therefore, the resource tracker already has all the information it needs to understand the *actual* overcommit ratio of CPU and memory on each compute node, regardless of the settings of the *maximum* overcommit ratio on a compute node (which is in each compute node's nova.conf).

Hope that makes things a bit clearer! Sorry for the confusion :)

[pmurray]: In the past, when debugging problems in our systems, I have found it useful to know what the free value actually is. So I think a percentage/ratio value would be less helpful to me as an operator. Additionally, if the message changed depending on the sign of the value it would make it harder to search for it in the logs. So from that point of view I would say the message is fine as it is. I can see that "free" being negative seems odd. Could add "(negative value means overcommitted resource)" to the message?

Paul

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