[PLUG] help with /proc/cpuinfo

Ben Koenig techkoenig at gmail.com
Sun Apr 28 22:25:18 UTC 2019


Forgive my ignorance in resurrecting this, but isn't the primary purpose 
of a VM to partition system resources?

Is this "noisy neighbor" problem a side effect of using VM's, or just 
bad VM management on the part of the host? This whole Cloud idea seems 
pretty pointless if a single VM is able to consume CPU time in the same 
way a normal process does. You might as well just give everyone a user 
account and let them fight over a shared pool of RAM.....


Just curious to know if the path forward in a situation like this is to 
blame the configuration or the technology itself. Would this be any 
different on a different hypervisor...etc.


On 4/25/19 1:17 PM, VY wrote:
> Hi Aaron
>
> Thanks for confirming.  I do not yet know how to troubleshoot in a Xen env
> but now that you
> dissected the data with me (which no one on our team has so far), I
> understand the situation now.
>
> There's no much I can do, and we do not have another place to migrate this
> image.
> Oh well....
>
> thanks again!
>
> -v
>
>
> On Thu, Apr 25, 2019 at 1:05 PM Aaron Burt <aaron at bavariati.org> wrote:
>
>> On 2019-04-25 10:54, VY wrote:
>>> Yes, I love to learn as well.
>>>
>>> This is the output to lscpu:
>>>    Architecture:          x86_64
>> [...]
>>> Hypervisor vendor:     Xen
>>> Virtualization type:   full
>> Ah-hah.  You're in a VM, and I'll bet you have a "noisy neighbor."
>>
>>> The load average is:
>>> load average: 464.68, 415.14, 416.96
>>> which does not make sense at all.
>> Loadavg is just how many processes are waiting to use the CPU.
>>
>>> The rest of TOP:
>>>    Cpu(s): 51.3%us, 16.0%sy,  0.0%ni, 32.0%id,  0.0%wa,  0.0%hi,
>>> 0.4%si,
>>> 0.2%st
>>>
>>> If I hit 1, it affects all 4 CPUs.
>> All good.  Very much looks like a "noisy neighbor" problem, which is
>> when another VM on the hypervisor is hogging all the CPU (or RAM) and
>> leaving you with no compute resources.  From your VM's perspective, it's
>> going at the rated clock speed, but time is going by REALLY FAST.
>>
>>> Can you elaborate on why
>>>   >    apicid : 25
>>>>    initial apicid : 25
>>> 25 is a weird number?   From an earlier thread, is this simply a
>>> logical
>>> ID?
>> Eh, sort of.  There should only be a couple APICs in the system.  And
>> usually it'll be pretty consistent.
>>    But since it's a VM all bets are off.
>>
>>> All the other systems are reporting this number as 4 and all of them
>>> are
>>> having reasonable load.
>> They're on a different hypervisor machine, and probably a different
>> version of the hypervisor software.
>>
>>> I do not have root access nor sudo.  I want to try and find out why
>>> the load is so high before I escalate and argue for more privilege.
>>> When I brought this up to the responsible team, I was given a probable
>>> cause -- There are other activities hosting this VM server and they are
>>> causing this issue.
>> So they already told you that you have a noisy neighbor.  All right
>> then.  Don't use that VM and get by on the 3 you have, or ask the team
>> to migrate your slow VM to a different hypervisor machine, or ask for a
>> new VM on a less loaded hypervisor machine.  But unless the noisy
>> neighbor calms down it sounds like your one sad VM isn't getting any
>> better.
>>
>> Is this a customer-facing service?  If so, you should point this out to
>> your hosting team.
>>
>> Good luck,
>>     Aaron
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