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

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Fri, Jan 01, 2010 at 10:51:48PM +0200, Pasi Kärkkäinen wrote:
> On Fri, Jan 01, 2010 at 03:06:03PM -0500, James Pifer wrote:
> > > You really need to start monitoring the server/dom0 in more detail.
> > > 
> > > Are you using file: backend for domU disks, or tap:aio: ?
> > > 
> > > -- Pasi
> > 
> > The domUs are all using file based storage. The memory did not fill up
> > until I started the domUs. 
> 
> Yes, exactly. When you start using file: backed domUs, then the dom0
> Linux kernel will start caching the guest disk accesses into the memory.
> 
> This is completely normal, and it's exactly what should happen. 
> 
> Like said, dom0 Linux kernel will use as much memory for caching as
> there's available to dom0 - so caching is not a reason to increase dom0 
> memory. 
> 2048 MB definitely is enough for dom0.
>

Just for reference, back in the Xen 2.0 days I used to have 192 MB of
RAM for dom0.. and that was enough.

Nowadays I usually give dom0 512 MB of RAM, or in bigger machines 1024 MB.
That is usually enough for a Xen-only server machine (without any local 
desktop/X use).

So.. you need to make sure there's nothing leaking memory in dom0. 
Xen management tools will obviously require some available memory in dom0 
to work correctly.

-- Pasi


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