Hi Francisco,
I've been trying to limit the cpu usage of a VM using cgroups - so I can
share my experience with you. However, from monitoring the kvm process
looks like it doesnt force a hard limit of cpu usage%. Hopefully, someone
can light up the issue.
I'm interested in limiting the io bandwidth of network and disk as well.
(dm-ioband - any experience with that? other suggestions?)
1. mount -t cgroup none /dev/cgroup -o cpu,memory
This creates the cgroup file system api on /dev/cgroup. The top level
hierarchy node contains all the processes by default.
2. cd /dev/cgroup
3. mkdir VM1
4. mkdir VM2
5. echo {kvm1 pid} > vm1/tasks
6. echo {kvm2 pid} > vm2/tasks
Moves the vm's processes from the top node to a child node - to enable
atomic control
7. edit VM1/cpu.shares and VM2/cpu.shares to change cpu proportion
(default is 1024 shares)
I've used 128 for VM1 and 1024 for VM2. To my understanding, that should
yield proportion of 128/(1024+128) < 15% of cpu limit for VM1.
Each of the VMs was allocated 2 vcpu, the host has 4 cores.(Been tring the
same with 1 vcpu each, results werent different)
Monitoring results:
I used top, atop and system monitoring GUI on the host and on the guest
for monitoring. Was able to load VM1 to use more than 50%...
(Monitoring screenshot at http%3A%2F%2Ftinyurl.com%2Fcsx3v7 ) On the left
- guest monitoring, time graph shows that there are peaks of more than
50%), on the right - host monitoring, kvm pid 32620 (VM1 pid) with 63%
load)
Regarding the references you asked for. Those are the references I've
found and worked with:
www.mjmwired.net%2Fkernel%2FDocumentation%2Fcgroups.txt%A0
http%3A%2F%2Ftinyurl.com%2Fdcnoav
- Oshrit
oshr...@il.ibm.com
From:
Brian Jackson <i...@theiggy.com>
To:
Francisco Mazzeo <francisco.maz...@gmail.com>, kvm@vger.kernel.org
Date:
03/04/2009 02:32
Subject:
Re: CPU Limits on KVM?
I haven't ever really used cgroups. I always figured a fair host scheduler
is
good enough to handle spreading load. So I don't know if it will fit
exactly
what you need. I don't think so. I also don't know of any other options. I
will say, If I gave 4 VMs a single cpu each on a 4 core host, I would
expect
the host to be fully loaded. I wouldn't see any reason for the host not to
be
fully loaded. That is after all one of the key points of virtualization.
Better utilization of hardware.
On Thursday 02 April 2009 17:33:07 Francisco Mazzeo wrote:
> Hello Brian,
>
> Thanks for the reply. is there a wiki about cgroupds and how to set
them
> up?
>
> Also, I tried just for kicks to see what would happen if I create 4
> Virtual Windows machines, run prime95 (a tool that does iterations
> like superpi to stress test memory/cpu) on all of them and just assign
> them only ONE core to them.
>
> The server node did not crash and you are right, however I was hoping
> for the server load to stay below 50% as I only gave it one single
> core to each KVM VE. Instead it seems like KVM let each VE get one
> slice of each of the 4 cores of my CPU, which did not accomplish what
> I wanted.
>
> Is cgroupds the only choice available?
>
> -- Francisco
>
> On Thu, Apr 2, 2009 at 3:29 PM, Brian Jackson <i...@theiggy.com> wrote:
> > There's CPU cgroups. It doesn't have exactly the ability you are
after,
> > but it is able to limit process(es) CPU usage. Maxing out CPU usage
won't
> > crash your server. The kernel will arbitrate sharing the CPU evenly
among
> > processes/VMs.
> >
> > --Brian Jackson
> >
> > On Thursday 02 April 2009 16:41:10 Francisco Mazzeo wrote:
> >> Hello,
> >>
> >> I am a new user to KVM and was wondering if there was any way to
> >> limit a VE from using up all the resources of the processor.
> >>
> >>
> >> Right now I have a Quad core 2.5Ghz, I have a KVM VE (running
windows
> >> server 2003) and assigned 4 CPUs to it. If I max out the load for
that
> >> VE, the entire host node load will be 100% which may crash it if I
> >> hosted more than 1 single VE.
> >>
> >> OpenVZ has cpulimit command, does KVM have something similar or any
> >> way that I can implement a limit on a single VE? Say I want to only
> >> give a max of 500Mhz per core, to total 2Ghz to the VE.
> >>
> >> Thanks
> >> Francisco
> >> www.navigatoris.net / www.serversoutlet.com
> >> --
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