RE: [Xen-devel] xl list vs xm list: backwards compatibility vs forward progress?

[Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>]

> From: Ian Jackson [mailto:Ian.Jackson@xxxxxxxxxxxxx]
> Sent: Wednesday, July 28, 2010 7:56 AM
> To: Dan Magenheimer
> Cc: Xen-Devel (xen-devel@xxxxxxxxxxxxxxxxxxx)
> Subject: Re: [Xen-devel] xl list vs xm list: backwards compatibility vs
> forward progress?
> 
> Dan Magenheimer writes ("[Xen-devel] xl list vs xm list: backwards
> compatibility vs forward progress?"):
> > I was pleased to find out that "xl list" shows the
> > current amount of physical memory in use by a domain
> > rather than the start amount.  This is very useful
> > for monitoring self-ballooning!  I like it!
> >
> > But... it is not backwards compatible with "xm list".
> 
> Isn't it ?
> 
> I'm pretty sure I've written a program which does "xm mem-set" and
> then polls the output from "xm list" to wait for the target domain to
> balloon down.

Hmmm... perhaps xm keeps track of xm mem-set commands... but a
domain can do ballooning without involvement of the toolchain.
Self-ballooning (see xen.hg/tools/xenballoon, in tree for about
two years now) does that in-guest-userland and I have kernel rpms
for EL5u5 and RHEL6b2 that do it in-guest-kernel.  (The latter
will be the preferred guest deployment method for Xen systems
running tmem to optimize memory utilization.)

With self-ballooning in a guest, xl list and xm list
very definitely show different values for memory.

Dan

P.S. Frankly, I think the xm list behavior is a bug, but
backwards compatibility -- plus my poor parseltongue --
stopped me from trying to fix it.

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