Re: [Xen-devel] [PATCH] linux/balloon: don't allow ballooningdowna domain below a reasonable limit

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 2/5/08 00:27, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

>> There are better ways to measure memory pressure - sizes of the various
>> active and inactive lists etc. OLPC has code for this and a proposed
>> memory pressure notifier feature that they use to allow user space apps
>> to cleanup.
> 
> Definitely agreed that vm_committed_space is just intended to be
> a first order approximation.  It also has the advantage of having
> been around awhile so that the balloon driver will work with many
> distros rather than require a TBD memory pressure indicator.
> 
> Alan, do you have a pointer to the proposed OLPC code?
> 
> Keir, I'm working on some xenbus support and will submit an
> updated patch, probably early next week.  I also have a horrible
> hack to work in a module, but I suspect that will get jettisoned. ;-)

Okay, I will comment when I see it. I'm not sure what design you are working
on: perhaps extract memory stats from the guest via xenbus and implement
ballooning policy in dom0? That is what I would prefer to see. The Novell
ballooning-limit checks were only added as a safety backstop in the guest
itself. Apart from tweaking it to make it less conservative where we are
confident that is safe, any more complicated policy, and of course and
cross-domain global optimisation, doesn't belong in the individual guests.

 -- Keir



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