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RE: [Xen-users] 'xm list' states

  • To: "Timo Benk" <timo.benk@xxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
  • From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
  • Date: Mon, 24 Apr 2006 13:55:37 +0200
  • Delivery-date: Mon, 24 Apr 2006 04:56:29 -0700
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Thread-index: AcZnk5bZGSblMQhQRcWA7V12ttZnCAAAWEWQ
  • Thread-topic: [Xen-users] 'xm list' states

> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Timo Benk
> Sent: 24 April 2006 12:38
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] 'xm list' states
> Hi,
> can someone explain the states shown by the 'xm list' command?
> 'r' (running) - The domain is currently running.
> - This flag is always shown for the Domain 0, but never for
>   unprivileged domains, why?

Presumably because you're on a single processor machine, you never see
anything other than Dom0 running (as Dom0 MUST be one running to show
the 'xm list' output). In a Multi-processor (multi-core/thread) system,
you could have more than one domain running at any given time.
Obviously, this assumes that the DomU(s) are actually DOING something,
(like "for((;;)) { ; }" in a shell) - if it's just sitting there waiting
for someone to send a net-packet or type on a keyboard, it wouldn't be

> 'b' (blocked) - The domain is blocked.
> - What does that mean? Why should a domain be blocked?

It's blocked waiting for something, usually an interrupt (for example,
waiting for hard-disk data to be passed over to the domain). Also,
things like "sleep 5" in the shell would cause "blocked", as the domain
is waiting for a number of timer ticks (5 seconds worth of) to pass. 

> 'p' (paused) - The domain is paused.
> - Ok, that one is easy, the domain was paused with 'xm pause'

> 'c' (crashed) - The domain has crashed.
> - If i do 'echo 1 > /proc/balloon' inside a unprivileged domain, i
>   will get a kernel panic. But the state says nothing about that? The
>   domain is definitively crashed, but the xm list command says nothing
>   about that. Why?

It may be that the crash isn't detected properly by hypervisor - I think
this may only work under some circumstances. I don't know for sure, I'm
just guessing here.

> 'd' (dying) - The domain is in the process of dying.
> - Well, poor little domain, but what does that mean?

Something has told the domain to "kill itself" (such as "xm
shutdown/destroy", but it's not yet disappeared. It's probably there for
the purpose of avoiding race-conditions where something is killing the
domain, and something else is talking to it (for example disk accesses),
and we don't want to retry operations that fail because the domain is
disappearing - where it would make sense to retry it on a "living"

> Maybe anybody here who can clearify the meanings of the 
> state. The manual page is not very helpful.

I hope this is of some help. 

> Many Thanks and greetings,
> -timo
> --
> Timo Benk
> PGP Public Key: http://vs241071.vserver.de/timo_benk_gpg_key.asc
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