[CentOS-virt] Cannot allocate Memory

[George Dunlap]

On Wed, Jun 22, 2016 at 6:45 PM, Shaun Reitan <shaun.reitan at ndchost.com> wrote:
> Any of you guys ever seen an issue with Xen 4.4 were xm cannot create a
> guest because of what looks like an issue allocating memory even though xm
> info shows like 5x the amount of free memory needed? We are still
> unfortunately still using xm... it's on my list, i know..
>
> We've had this happen on a couple hosts now.  Only way to resolve seams to
> be rebooting the host.  I'm going to update the host to latest Xen 4.4 now
> hoping this is a old bug.

xend hasn't had much love in years, so it's fairly unlikely that this
has been fixed.

> Here's from xen logs
>
> [2016-06-22 09:13:50 1958] DEBUG (XendDomainInfo:105)
> XendDomainInfo.create(['vm', ['name', 'xxx'], ['memory', 2048],
> ['on_xend_start', 'ignore'], ['on_xend_stop', 'ignore'], ['vcpus', 2],
> ['oos', 1], ['image', ['linux', ['kernel', '/kernels/vmlinux-2.6.18.8-4'],
> ['videoram', 4], ['args', 'root=/dev/xvda ro xencons=tty console=tty1 '],
> ['tsc_mode', 0], ['nomigrate', 0]]], ['s3_integrity', 1], ['device', ['vbd',
> ['uname', 'phy:vg/fs_6818'], ['dev', 'xvda'], ['mode', 'w']]], ['device',
> ['vbd', ['uname', 'phy:vg/fs_6819'], ['dev', 'xvdb'], ['mode', 'w']]],
> ['device', ['vif', ['rate', '40mb/s'], ['mac', 'FE:FD:48:01:F1:E7']]]])
> [2016-06-22 09:13:50 1958] DEBUG (XendDomainInfo:2504)
> XendDomainInfo.constructDomain
> [2016-06-22 09:13:50 1958] DEBUG (balloon:187) Balloon: 7602632 KiB free;
> need 16384; done.
> [2016-06-22 09:13:50 1958] ERROR (XendDomainInfo:2566) (12, 'Cannot allocate
> memory')
> Traceback (most recent call last):
>   File "/usr/lib64/python2.6/site-packages/xen/xend/XendDomainInfo.py", line
> 2561, in _constructDomain
>     target = self.info.target())
> Error: (12, 'Cannot allocate memory')
> [2016-06-22 09:13:50 1958] ERROR (XendDomainInfo:490) VM start failed
> Traceback (most recent call last):
>   File "/usr/lib64/python2.6/site-packages/xen/xend/XendDomainInfo.py", line
> 475, in start
>     XendTask.log_progress(0, 30, self._constructDomain)
>   File "/usr/lib64/python2.6/site-packages/xen/xend/XendTask.py", line 209,
> in log_progress
>     retval = func(*args, **kwds)
>   File "/usr/lib64/python2.6/site-packages/xen/xend/XendDomainInfo.py", line
> 2572, in _constructDomain
>     raise VmError(failmsg)
> VmError: Creating domain failed: name=xxx
> [2016-06-22 09:13:50 1958] ERROR (XendDomainInfo:110) Domain construction
> failed
> Traceback (most recent call last):
>   File "/usr/lib64/python2.6/site-packages/xen/xend/XendDomainInfo.py", line
> 108, in create
>     vm.start()
>   File "/usr/lib64/python2.6/site-packages/xen/xend/XendDomainInfo.py", line
> 475, in start
>     XendTask.log_progress(0, 30, self._constructDomain)
>   File "/usr/lib64/python2.6/site-packages/xen/xend/XendTask.py", line 209,
> in log_progress
>     retval = func(*args, **kwds)
>   File "/usr/lib64/python2.6/site-packages/xen/xend/XendDomainInfo.py", line
> 2572, in _constructDomain
>     raise VmError(failmsg)
> VmError: Creating domain failed: name=xxx

If you haven't decided to switch to xl, would you mind reposting this
question to xen-users?  If you do, please also include the output of
"xl info" after the failure.

The logs tell us that xend is asking dom0 to free up some memory to
use to create the guest.  My guess is that there's a slight mismatch
between how much memory xend things needs to be freed and how much
memory actually needs freeing.

Thanks,
 -George