[one-users] Nice & Priority control on disk access

[Carlos Jiménez]

Thanks Ruben.

I've realised that lower performance takes place each time a new VM is 
in PROLOG status or when I create/clone an image. I guess all that is 
related to disk access. As a testing purpose, I've cloned an image and 
executed iotop in the server where OpenNebula and NFS Server are running.

This is a sample output:

    PID  PRIO  USER     DISK READ  DISK WRITE  SWAPIN     IO> COMMAND
  3238 be/7 oneadmin 1783.88 K/s 1783.88 K/s  0.00 % 93.98 % cp -f 
/var/lib/one/datastores/1/9fedfe0d5cb02961~ne/datastores/1/72da3ba9d86fdc573b944c03253561ae

Sometimes, there is another process (flush-147:0) with an important IO 
usage:
    PID  PRIO  USER     DISK READ  DISK WRITE  SWAPIN     IO> COMMAND
  8028 be/4 root     1358.87 B/s    7.96 K/s  0.00 %  4.15 % [flush-147:0]


How could I set an "ionice -c 3" to that "cp" command? I would like to 
do it in a global and persistent way so that future cp actions (due to 
creation or cloning of a VM or an image) have a lower ionice, not just once.
Perhaps, I should set ionice in the driver configuration "exporting" a 
new global variable in /etc/one/defaultrc in the same way as the 
priority, shouldn't I? But, how do I configure ionice to interact with 
the proper driver?


Thanks for your help.

Carlos.


On 11/13/2012 11:51 AM, Ruben S. Montero wrote:
> Hi
>
> OpenNebula drivers are the piece of software that deals with the 
> underlying subsystems. Each driver starts a new thread/process for 
> each operation that should inherit the driver priority.
>
> If you take a look to /etc/one/defaultrc, you can change the CPU 
> priority assigned to the drivers. It defaults to 19, the least 
> favorable to the process. You may want to try to use sets other io 
> scheduling algorithm with ionice, or the blk module of cgroups.... or 
> any other tool to adjust the I/O priority of a process.
>
> Cheers
>
> Ruben
>
>
>
>
> On Mon, Nov 12, 2012 at 5:59 PM, Carlos Jiménez 
> <cjimenez at eneotecnologia.com <mailto:cjimenez at eneotecnologia.com>> wrote:
>
>     Hi all,
>
>     I have a server running OpenNebula 3.8 and acting as NFS server
>     for storaging with another host (running KVM and acting as a NFS
>     client for the storage). I have one VM running and then I try to
>     create another VM using Sunstone. Then, the running VM reduces its
>     performance while the creation of the new VM takes places. I guess
>     OpenNebula I/O processes on the shared disk have better
>     priority/nice/ionice than disk access of the already running VM.
>     The question is: Is there any way to control it so running VMs
>     don't decrease their performance? How do you reduce
>     priority/nice/ionice of the creation of the new VMs?
>
>     Thanks in advance,
>
>     Carlos.
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>
>
>
>
> -- 
> Ruben S. Montero, PhD
> Project co-Lead and Chief Architect
> OpenNebula - The Open Source Solution for Data Center Virtualization
> www.OpenNebula.org <http://www.OpenNebula.org> | 
> rsmontero at opennebula.org <mailto:rsmontero at opennebula.org> | @OpenNebula

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