cpu_cap and cpu_weight

Submitted by chmlro on Sun, 01/31/2010 - 06:20

Hi Jamie,

We've just aquired an entry license for cloudmin and we're evaluating it right now. A couple (or more) of questions for now:

  1. With what type of virtualization would you say Cloudmin works best? Or what is your personal favourite? We're linux users (Centos mainly) so we're more interested in the linux land.
  2. During the creation of a Xen instance/domU I was asked to provide a "Maximum CPU use" value. Considering the hw node is a quadcore(4x100?), I entered "300", however in the .cfg file for that domU I see no cpu_cap or cpu_weight entries on which we have been heavily relying when setting up the VMs manually.
  3. Related to nr. 2, is there a way to have different plans given different cpu_cap and cpu_weight?

That's it for now, i'll come with more issues later, as I will keep playing with Cloudmin.

Thank you.

Status: 
Closed (fixed)

Comments

Submitted by chmlro on Sun, 01/31/2010 - 06:38

Ah, one more thing:

We keep our dom0_mem at 512 MB or 1 GB so Cloudmin says the free memory is whatever is left free of those values. Shouldn't it use xm/xentop to find out available memory on the node?

Submitted by JamieCameron on Sun, 01/31/2010 - 20:37

1) I would recommend Xen if you want the best isolation between virtual systems, or OpenVZ if you want to pack the most VPSs into a host. From what I've seen, most customers use Xen.

2) Cloudmin actually sets the CPU cap and weight when the Xen instance is started, as until recently it wasn't possible to set those in the Xen config file. However, since that appears to have changed I will fix it in the next release (4.0).

3) You can set a limit on total CPU in a plan, which customers on that plan can then hand out to their virtual systems. So if the plan CPU limit was 150, a custom could create 3 systems each with a limit of 50 ... or 1 system with a limit of 150.

Regarding the free memory, which page are you looking at for this?

Submitted by chmlro on Mon, 02/01/2010 - 02:14

Hi Jamie,

I guess I'll have to dig more in cloudmin, to see how things work. For us it's very important to have caps and weights on cpu. Regarding the free memory, this is also important, so we know on which hw node we can create new xen instances. If you add a physical machine and then go to "Edit System", it will show resources. If I don't set dom0_mem it displays the memory properly and I can see how much is free. I will attach a screenshot of the capped dom0_mem (ignore the ridiculously huge swap size :> ).

Any ETA on Cloudmin 4.0?

Thank you.

Submitted by JamieCameron on Mon, 02/01/2010 - 12:29

Ok, I see what you mean .. all my test systems don't have dom0_mem set, so Cloudmin can see how much RAM is really free.

Is there some advantage to setting dom0_mem ?

Submitted by chmlro on Wed, 02/03/2010 - 08:41

Well, yes there is an advantage. The memory that is allocated through dom0_mem cannot be allocated so we stay on the safe side, and also I believe that parsing the output of xentop (maybe in the batch mode) is a better way of displaying memory usage.

Another question, we're used to the old paradigm of one package/vps per plan. Is there a way to limit a user to only create 1 vps with his plan?

Thank you.

Submitted by JamieCameron on Wed, 02/03/2010 - 17:33

Yes, it sounds like xentop is the way to go.

What does that output on your system with only 512M for the dom0 ?

Also, it is quite possible to create a plan that only allows the creation of a single system.

Submitted by chmlro on Thu, 02/04/2010 - 03:23

Hi Jamie,

I made some captures of the xentop utility that I will attach to this issue. Now that I look at them I can already see a problem, I don't see the output of total/used/free memory of the node in batch mode which is the preferred way to gather data.. Also the domU's names are truncated.

One more question slightly unrelated, in case of KVM nodes, how do you limit the cpu usage of a virtual machine?

Thank you.

Submitted by JamieCameron on Thu, 02/04/2010 - 12:55

That's odd, when I run xentop -i 1 -b it does output the all-important Mem: line. This is on CentOS 5.4 with the supplied Xen packages..

For kVM, there doesn't appear to be any way to limit CPU use.

Submitted by chmlro on Thu, 02/04/2010 - 13:28

Maybe that's the problem, I don't use stock xen but the latest stable from gitco.de..

Submitted by JamieCameron on Thu, 02/04/2010 - 13:38

Which version is that? I've added code to use the xentop output, but if it doesn't show real total memory it won't be much good ..

Submitted by chmlro on Thu, 02/04/2010 - 15:07

Jamie,

Don't be hasty, if the memory thing is not available on all versions of xen, then maybe it's not worth it. I use xen 3.4.2 from here http://www.gitco.de/repo/

Submitted by JamieCameron on Thu, 02/04/2010 - 15:31

I'll have Cloudmin fall back to the current behavior if xentop doesn't give me what I want..

Submitted by chmlro on Thu, 02/04/2010 - 17:51

Yeah, so I guess I'm back to square one. :-) I will try to investigate why xentop from 3.4.2 doesn't report all the total memory and will get back to you. Thanks a lot.

Submitted by chmlro on Tue, 02/09/2010 - 14:48

Hi again,

I'm returning with more info on this issue. Apparently one can get the total memory available to xen and the free memory via xm info. e.g.

total_memory : 8090 free_memory : 820

So no more messing around with xentop, at least not for this issue.

Hopefully this will make it in the next release.

Submitted by JamieCameron on Tue, 02/09/2010 - 18:26

Thanks, I will use xm info in the next Cloudmin release (4.0)

Submitted by Issues on Tue, 02/23/2010 - 20:19

Automatically closed -- issue fixed for 2 weeks with no activity.