Re: [Xen-devel] libxl: error: libxl.c:2150:libxl_set_memory_target new target 0 for dom0 is below the minimum threshold

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Wed, 23 Nov 2011, Ian Campbell wrote:
> On Wed, 2011-11-23 at 13:57 +0000, Stefano Stabellini wrote:
> > On Wed, 23 Nov 2011, Ian Campbell wrote:
> > > > > On the other hand I'm not sure why autoballoon and dom0_mem play so
> > > > > badly together. Surely if dom0_mem is used autoballon should just see
> > > > > that there is plenty of free RAM in the system and not do anything?
> > > >  
> > > > Because one of the "memory slack" paramters needed by autoballoon is
> > > > 
> > > > totalmemory - dom0_memory_at_boot
> > > 
> > > libxl gets dom0_memory_at_boot via the dominfo (in
> > > libxl__fill_dom0_memory_info which I assume happens before any
> > > potentially autoballooning) which should take dom0_mem into account,
> > > doesn't it?
> > 
> > It does, in the sense that the memory slack is trimmered to max 15% of
> > total memory.
> > Basically there is no way to calculate this parameter if dom0_mem is
> > set, so we conservatively set it to 15%.
> 
> What I meant was that dom0_memory_at_boot comes from
> XEN_SYSCTL_getdomaininfolist and is therefore the value of the dom0_mem
> parameter (give or take a wiggle, I suppose), when called from
> libxl__fill_dom0_memory_info (i.e. before any auto ballooning has taken
> place). In other words there is a way to calculate this parameter...

we don't want to know the value of the dom0_mem parameter, we need the
amount of memory dom0 would have if dom0_mem was NOT passed to Xen.

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