Re: [Xen-devel] [PATCH] RFC: initial libxl support for xenpaging

[Olaf Hering <olaf@xxxxxxxxx>]

On Mon, Feb 20, George Dunlap wrote:

> xl mem-set domain M
>  xenpaging off: Set balloon target to M
>  xenpaging on: Set paging target to M
>  xenpaging delay: Set balloon target to M, and wait for actual memory
> to reach M.  If it hasn't reached it by $paging_delay seconds, set
> balloon target to M.

The tristate instead of a boolean is not really needed as well.

Right now a reduction of the balloon target depends on how fast the
guests balloon driver can claim memory from the guest OS. This means it
could take an infinite amount of time to reach the requested target.
With paging the request to reduce the "footprint" can be reached as fast
as xenpaging can page-out gfns (and page-in busy gfns).

So having a delay or not seems to depend on how mem-set is supposed to
react, either now or at an (kind of) undefined time in the future. 

If "now" is not the desired mode then xenpaging can slowly work toward a
new lower target by calling its evict_pages() with low numbers and and
an adjustable delay between calls.


Olaf

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