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Re: [Xen-devel] libxl/xl memory paging/sharing/ballooning/etc proposal.

On Thu, Mar 15, Andres Lagar-Cavilla wrote:

> > 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).
> It is /local/domain/X/memory/target-tot_pages. I agree it should not be
> guest visible, and we're still in time to change it.

Is it guest visible? I think the entry point for a guest is /vm/<uuid>/,
I'm almost sure it can not get to /local/domain/X/memory/

> /libxl/X/memory-policy/paging-target? Is there a non-libxl
> non-/local/domain path xenpaging could look into, should it be launched
> autonomously? Olaf, do you care about xenpaging in non-libxl environments?

xenpaging needs to read its target from somewhere, I dont think this has
anything todo with libxl or not.

> >         XXX libxl_domain_paging_enable here or on domain build / policy
> >         set? libxl_domain_paging_enable is idempotent so calling it here
> >         is always safe?
> You can enable the pager on build, unless the actor settings preclude it.
> Then all you need to do to get the pager to work is write its xenstore
> key.
> But generally speaking, the pager might have been disabled ex xl-machina,
> so you really want to be able to test_and_set the pager here.
> Olaf, does xenpaging have standard daemonize behavior of locking a
> /var/foo/pid file?

It writes its pid to xenstore and announces its state in
xenpaging/state, like qemu-dm does. Thats in my libxl support patch at


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