Re: libxl/xl memory paging/sharing/ballooning/etc proposal.

[Olaf Hering <olaf@aepfle.de>]

On Thu, Mar 15, Ian Campbell wrote:


> low level libxl interface
> -------------------------
> 
> It is expected that toolstacks primary user interface will be via the
> above high level interface. The lowlevel interface is provided in order
> to allow implementation of memory policy actors using libxl and to allow
> toolstacks to optionally provide an interface for expert users to shoot
> themselves in the foot with ( ;-) )
> 
> libxl_domain_(set|get)_balloon_target(ctx, domid, target_memkb, relative, enforce):
>         
>         Read/write /local/domain/X/memory/target to control the in guest
>         balloon driver. This is basically the existing
>         libxl_domain_memory_target with a new name
>                 
>         As before this is a request to the guest balloon driver to try
>         and use this much actual RAM. This is an existing guest
>         interface which we cannot change.
> 
> libxl_domain_(set|get)_paging_target(ctx, domid, target_memkb, relative)
> 
>         Read/write whichever XS path controls the xenpaging daemon's
>         target. (Olaf?). I think this path should not be
>         under /local/domain since it should not be guest visible
>         (probably it already isn't).

Its currently /local/domain/X/memory/target-tot_pages, but can still be
changed if needed.

>         It is an error to call this for a PV guest (ERROR_??) for a
>         guest which does not have paging enabled
>         (ERROR_PAGING_DISABLED?).

Error is ok.

> libxl_domain_(enable|disable)_paging(ctx, domid)
> 
>         Idempotently starts or stops the xenpaging daemon for a domain.

In what context should this run?
In case of 'xl $enable_paging' it would be good if this acts as a
trigger for the xl monitoring process, so that the pager is a child of
the monitoring process.

Olaf