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Re: [Xen-users] Memory problems persist... Cannot allocate memory

On Fri, Jan 01, 2010 at 10:59:00AM -0500, James Pifer wrote:
> > For example "top", sort by memory usage by pressing shift+m.
> > Or just the usual "ps aux" output.
> > 
> > -- Pasi
> 
> Happy New Year!
> 

Happy new year to you too!

> This morning I went to look at the memory being used and box was locked
> up requiring a hard reset. Thankfully everything came back up ok. Upon
> reboot dom0 now has 2gb of RAM. So I started bringing up my domUs. 
> 

You definitely have something wrong.. you really shouldn't run out of
ram in dom0 and definitely shouldn't crash.

> After starting about half of them the available RAM was already used!!!
>

Well WHAT in dom0 was using all the RAM? 
Please figure that out.

Was it some process, or just memory cache? 

> Having plenty of available RAM with 32gb total, I shut down the domU's
> and bumped the RAM to 4gb to see what would happen. I now have all 15
> domUs started, and it sucked up all available RAM, except for the 2gb of
> swap, which is mostly free. 
> 
> The server runs in runlevel 3, but I do run a vncserver session because
> I'm remote. Even so, the gnome session does not appear to be taking up
> much memory. As a matter of fact, if I do a ps aux and add up the memory
> column, it only comes out to a little over 8%, so I don't understand
> what's happening. 
> 
> top now shows me:
> top - 08:52:34 up 24 min,  2 users,  load average: 0.71, 1.46, 2.70
> Tasks: 303 total,   1 running, 302 sleeping,   0 stopped,   0 zombie
> Cpu(s):  0.9%us,  0.8%sy,  0.0%ni, 92.4%id,  5.4%wa,  0.0%hi,  0.0%si,  0.5%st
> Mem:   4192768k total,  4154732k used,    38036k free,    78084k buffers
> Swap:  2104472k total,      112k used,  2104360k free,  3565872k cached
> 

Well you have 3,5 GB in disk caches (3565872k cached), so you don't have 
much RAM at all in use in dom0.

You know Linux uses all/most of the free memory as disk cache
automatically? 

So if you grow dom0 memory the end result is that dom0 Linux will just
use more memory as disk caches.

You really need to figure out what was using all the memory and swap
earlier.

> My domU's are:
> Name                  Mem    VCPUs
> Domain-0             4094    16  
> windows2k3           2048     2  
> windows2k            1024     1  
> sles10               2048     2  
> sles10               1024     4  
> sles10               2048     2  
> windows2k3           1024     1  
> windows2k3           2048     1  
> sles10               1024     2  
> win2k8               2048     4  
> windows2k3           1536     1  
> windows2k3            512     1  
> windows2k3            512     1  
> windows2k3            512     1  
> windows2k3           1024     1  
> windows2k3            512     1  
> 
> Any thoughts? 
> 

You really need to start monitoring the server/dom0 in more detail.

Are you using file: backend for domU disks, or tap:aio: ?

-- Pasi


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