Re: [Xen-devel] Proposed new "memory capacity claim" hypercall/feature

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.10.12 at 16:43, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> wrote:
> With tmem, memory "owned" by domain (d.tot_pages) increases dynamically
> in two ways: selfballooning and persistent puts (aka frontswap),
> but is always capped by d.max_pages.  Neither of these communicate
> to the toolstack.
> 
> Similarly, tmem (or selfballooning) may be dynamically freeing up lots
> of memory without communicating to the toolstack, which could result in
> the toolstack rejecting a domain launch believing there is insufficient
> memory.
> 
> I am thinking the "claim" hypercall/subop eliminates these problems
> and hope you agree!

With tmem being the odd one here, wouldn't it make more sense
to force it into no-alloc mode (apparently not exactly the same as
freezing all pools) for the (infrequent?) time periods of domain
creation, thus not allowing the amount of free memory to drop
unexpectedly? Tmem could, during these time periods, still itself
internally recycle pages (e.g. fulfill a persistent put by discarding
an ephemeral page).

Jan


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