Re: Cannot allocate Memory

["Shaun Reitan" <shaun.reitan@xxxxxxxxxxx>]

We are planing on moving to xl but have not done so yet.

Our xend configs are untouched so they should match what they were when 
the xen-* packages were installed.

We force dom0 to 1024MB of memory via grub.

On a couple servers were we've seen this issue we've had 16+ GB of 
memory free and the domU was requesting something small like 2GB.

--
Shaun



------ Original Message ------
From: "George Dunlap" <dunlapg@xxxxxxxxx>
To: "Shaun Reitan" <shaun.reitan@xxxxxxxxxxx>; "Discussion about the 
virtualization on CentOS" <centos-virt@xxxxxxxxxx>
Sent: 6/24/2016 4:28:53 AM
Subject: Re:  Cannot allocate Memory

> On Wed, Jun 22, 2016 at 6:45 PM, Shaun Reitan 
> <shaun.reitan@xxxxxxxxxxx> 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

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