[PLUG] help with /proc/cpuinfo

Sun Apr 28 23:17:26 UTC 2019

On 4/28/19 3:25 PM, Ben Koenig wrote:
> 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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>>>
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There are only so many "clock ticks" to go around on any system. The 
purpose of a VM is to distribute those as efficiently as possible. 
However, if one of the "neighbors" is able to consume too much time, or?? 
there are a lot of them, then a reconfiguration for load balancing is in 
order.?? As was already pointed out, this is something the managers of 
your VM/Hypervisor needs to address. if they are unable or unwilling, 
there isn't much you can do except have them move you to an alternative?? 
server or find a different hosting service that will respond to your needs.

The bottom line: is the under-performance of the one server a detriment 
to the site(s) or service(s) you are providing or is it just an 
annoyance??? You will probably have to document the impact of the one 
server on your users and see if your provider will address it.

~~R