Re: [Xen-devel] [RFC][PATCH] 0/9 Populate-on-demand memory

[Tim Deegan <Tim.Deegan@xxxxxxxxxx>]

At 15:46 +0000 on 24 Dec (1230133560), George Dunlap wrote:
> On Wed, Dec 24, 2008 at 3:35 PM, Dan Magenheimer
> <dan.magenheimer@xxxxxxxxxx> wrote:
> >> We could to allocate a new page at that point; but it's likely that
> >> the allocation will fail unless there happens to be memory lying
> >> around somewhere, not used by dom0 or any other doamin.  And if that
> >> were the case, why not just start it with that much memory to begin
> >> with?
> >
> > Actually, if dom0_mem is used rather than the default of letting
> > domain0 absorb all free memory and dole it as needed to launching
> > VMs, there will almost always be some memory lying around.
> 
> At any rate, I suppose it might not be a bad idea to *try* to allocate
> more memory in an emergency.  I'll add that to the list of
> improvements.

Please don't do this.  It's not OK for a domain to start using more
memory without the say-so of the tool stack.  Since this emergency
condition means something has gone wrong (balloon driver failed to
start) then you're probably just postponing the inevitable, and in the
meantime you might cause problems for domains that *aren't* misbehaving.

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

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