Re: [Xen-users] using maxmem

[Alexandre Chapellon <a.chapellon@xxxxxxxxx>]

Made some tests to illustrate what I said in my previous mail.
I counting time to reach the splash screen of windows installer using different value of maxmem (nothing else changed):

- no maxmem / mem= 2048
33 sec.

- maxmem=2048 / mem =2048
33 sec

- maxmem=4096 / mem =2048
1 min 57 sec

- maxme=8192 / mem =2048
4 min 32 sec

nobody has a clue?

Le 15/12/2011 17:17, Alexandre Chapellon a écrit :

Hi,

I am using xen 4.0.1 from debian Squeeze repositories and dom0 has kernel 2.6.32-5-xen-amd64(also stock debian).
I wanted to set a high value to maxmem in my xmdomain.cfg vm config files so that I can increase memory as needed without rebooting.
Unfortunately as soon as I set this paramater I see really wiered things.
For example, I am trying to install a windows HVM guest. When maxmem is not set, the first screen of the installer appear after less than 30. If I set maxmem to 12288 (12GB, i guess), the installer screen takes more than 3min30sec to splash...
I have also tried to decrease maxmem to 8GB then 4GB (while memory=2048)... but that doesn't help... Well I have to say that the lower maxmem is set, the faster the VM are.
But when set the VM are generally slow and unstable, as I did not succeded to complete any installl because of guests crashing.
Not sure if it's related but, few times ago, I had an issue while doing live migration of a PV guest (migration seemed OK but VM was frozen) that also had maxmem set to such a value...  I never experienced livemig problem like this before...

Is there any options that may be incompatible with maxmem? Or am just doing bad use of maxmem?

Did anybody experienced similar behaviour?

Regards

--

Alexandre Chapellon

Ingénierie des systèmes open sources et réseaux.
Follow me on twitter: @alxgomz

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