RE: [Xen-devel] More on 2.6.28 and balloon driver

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

Hi Jeremy --

It appears that in the upstream balloon driver,
the call to HYPERVISOR_update_va_mapping is missing
from decrease_reservation.  I think as a result,
the balloon driver is eating memory but not
releasing it to Xen, thus rendering the balloon
driver essentially useless.  (Can be observed via xentop.)

Is this just a bug/oversight, or was there maybe
a problem pushing this code upstream?

Thanks,
Dan

P.S. Also please see related balloon driver thread
on xen-devel yesterday (Jan 06).

> -----Original Message-----
> From: Dan Magenheimer 
> Sent: Tuesday, January 06, 2009 5:53 PM
> To: Xen-Devel (E-mail)
> Subject: [Xen-devel] More on 2.6.28 and balloon driver
> 
> 
> Can't prove it yet, but it appears that when 2.6.28
> is ballooned to use less memory, the pages aren't
> actually returned to the domain's available pool
> of memory in Xen.
> 
> I've got some code (to be posted soon) that does
> an alloc_domheap_pages(d,0,0) after domain d balloons
> to use less memory.  The code works with linux-2.6.18-xen
> and linux-2.6.27-xen, but not with 2.6.28... the
> allocate fails.
> 
> Any good reason why this might be different?  Or should
> I dig for a bug / code difference?
> 
> Also, I am still on xen 3.3.0+ so if this was fixed
> later, please let me know.
> 
> Dan
> 
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