Re: [Xen-devel] question on balloon driver

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> It depends on what you mean by automatic.  I'm not sure anyone has ever
> posted an automated memory balancer.

One fine day, someone should write this.  It'd allow you to trade off a bit of 
isolation for a bit of statistical multiplexing in the case where your 
domains don't have a paranoid mistrust of each other.

VMware ESX sets a minimum, a maximum and a target percentage share for each 
machine.  It then does sampling of the domains to find out how much of their 
memory they're *really* using.  If they're not using all of it, they get told 
to give it back using the balloon driver and it's apportioned to domains that 
are using their memory more heavily.

This sort of thing should carry fairly straightforwardly across to Xen.  We 
could simply get domains to report their current utilisation through the 
store without needing to do sampling behind their back.

Could be a fun project for someone looking to get into Xen stuff (yes, that's 
an unsubtle hint to the world at large :-) ).

Cheers,
Mark

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