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

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 1/5/08 00:49, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> I'm experimenting now with an algorithm which starts
> with vm_committed_space* and adds back in a (for
> now) fixed fraction of 1/32 of total physical
> memory.
> 
> Dan
> 
> * Alas this is not exported so won't work in a module,
> but it seems to be a pretty good estimator of active
> virtual memory usage.

Can't vm_committed_space grow *bigger* than available memory when using
swap? It may indicate the 'static' demand for memory (in terms of requested
allocations so far) but we're interested in dynamic demand (how much of that
allocated memory is actually used), which afaics vm_committed_space doesn't
appear very useful for.

Some indication of paging churn, or average age of pages in memory, or
something like that, would seem more useful (albeit arbitrarily harder to
work out from within the balloon driver!).

Maybe I'm missing something. I've only had a quick look at usage of
vm_committed_space.

 -- Keir



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