Re: [Xen-users] Balloon Driver Documentation/Description

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> i'm looking for some documentation on how the balloon driver works
> internally.
>
> Can anybody give me a hint were i can find some good doku?

Some of the papers on Xen (see "Xen and the art of virtualisation", for 
instance) describe this, but not in much detail.  The idea actually came from 
VMware's ESX server product originally.

> I searched wiki.xensource.com and google but was not very successfull.

The code is also good documentation, if a little hard to follow before you 
know what it does.

Basically, the balloon driver allocates memory using standard kernel 
allocation functions, then gives it back to Xen.  The memory is no longer 
available to use in the guest at this point, and the fact that it was 
allocated by the balloon driver prevents the rest of the kernel from trying 
to use it.

When the balloon driver reclaims memory, it gets it back from Xen and then 
does a "free", allowing the kernel memory allocator to give it to other 
drivers for normal use.

The balloon driver contains a load of book keeping regarding these operations, 
certain mechanics to actually make the whole thing work properly, and a few 
other memory operations that are used by Xen drivers.

HTH some,
Cheers,
mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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