[Discuss] issue with mysql in a VM on Ubuntu 14.04.4 LTS

[gaf at blu.org (Jerry Feldman)]

My friend got back with some information.

This is a dedicated web server VM (virtual machine) running Ubuntu 14.04
LTS.  This is only running a single site, yet CPU usage reaches 100%
with only a few simultaneous users viewing the site.  Looking deeper it
appears that MySQL is using the majority of the CPU resources.  When
this happens, the hosted website is extremely slow or unavailable. 
Restarting the Apache and MySQL services temporarily helps, but a reboot
seems to have a longer effect. 

In troubleshooting the issue we have made several changes to various
conf files to increase buffers, caches, memory limitations, etc.

 The VM has 6 virtual processors assigned and 6 GB of RAM (statically
assigned).  The website is running WordPress with a MySQL back-end.  The
MySQL database is about 1 GB in size (see image below gaf:images remove
for listserv). 

The host is a Windows Server 2012 R2 server with the Hyper-V role.  It
has two Xeon E5-2640 CPUs and 128 GB of RAM (46 GB free).  The host is
performing nicely as are all other VMs hosted on it. 


gaf: I have a few ideas, such as giving mysql more memory, and maybe
fewer vCPUs.


On 03/29/2016 11:58 AM, Jerry Feldman wrote:
> Thanks Dan,
> yes I know. Looks to me that there might be a deadlock. But, with that
> short description there is no way to really diagnose.
>
> On Tue, Mar 29, 2016 at 9:31 AM, Dan Ritter <dsr at randomstring.org> wrote:
>
>> On Tue, Mar 29, 2016 at 08:51:40AM -0400, Jerry Feldman wrote:
>>> Essentially this is in a virtual machine (probably Microsoft) He has 6
>> CPUs
>>> assigned to the Ubuntu VM. Not sure of the memory. On occasion all the
>> CPUs
>>> are pegged at 100%. I've asked him for some additional details, such as
>>> memory configuration, physical server configuration, and if he can run
>> top
>>> or some other tools.
>>>
>> Without any further diagnostics, the problem is insoluble.
>>
>> However, I would bet a shiny nickel it has to do with I/O more
>> than CPU.
>>
>> -dsr-
>>
>
>

-- 
Jerry Feldman <gaf at blu.org>
Boston Linux and Unix
PGP key id:B7F14F2F
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