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RE: [Xen-devel] DOM0 memory allocation


> In the unstable tree the default memory allocation for DOM0 is now
> *all* available memory (rather than the somewhat underwhelming
> previous default of 16MB).
> This ought to be a much more useful default, but you must remember to
> 'balloon down' DOM0's memory reservation before creating new domains!
> The interface file is /proc/xen/balloon.

As well as the allocation for the domain, make sure you give Xen some
slack to play with when you begin starting domains. Xen's per-domain
memory requirements are normally very small (32KB), but when you start a
live-migration of a domain Xen will need memory to store shadow page
tables for the duration of the migration.

We really need to update the tools to autmoatically balloon down domain
0 and leave some approprite slack for Xen (e.g. maybe 16MB total for the
system by default). Volunteers? 

We also need to audit Xen's out of memory paths to make sure they're
handled appropriately. (The forthcoming shadow mode checkin should
handle that path rather better).


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