oops. forgot to put kvm-devel.
/Jd
Note: forwarded message attached.
---------------------------------
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Check outnew cars at Yahoo! Autos.--- Begin Message ---
Thanks Daniel. But I was looking for bit of under the hood answers.
Does libvirt use ps -ef | grep qemu to find out qemu processes ? Or it manages
only ones that are started using libvirt. Using some naming scheme.
How do you know if a running process is using kvm kernel module or not ?
libvirt seems to be connecting to qemu console through qemud ? right ? You
have done quite a bit of work to send command and parse. !! Isnt this error
prone ? (will code for parsing work in different char set ? or qemu console is
always guarenteed to be in english ?)
How do you find out what % of allocated memory is actually used by VM ?
For cpu /proc seems to be used.. which seems fine, but will not work for QEMU
on Windows.
Some core qemu quesions still remains
-- what are the plans to dynamically be able to change cpu , mem, disks and n/w
for a running vm ?
-- proper shutdown/restart of VM ?
Hoping some kvm/qemu experts would thrown in some light on the directions and
plans.
Thanks in advance.
/Jd
"Daniel P. Berrange" <[EMAIL PROTECTED]> wrote: On Fri, Apr 27, 2007 at
02:29:52PM -0700, jd wrote:
> Hi
> This is a great project with a lots and lots of potential. I have a
> bunch of questions related to managing kvm VMs.
>
> I would like to know what kind of options are available for doing
> effective management ot KVM/QEMU processes (VMs). And know more abut
> plans / roadmap /directions to get to a proper API. (similar to Xen-API)
We are supporting QEMU / KVM management in libvirt since version 0.3.0
aiming to have feature parity for our management APIs between Xen, QEMU
and KVM. This gives a C, Python & Perl API. A command line tool virsh.
And a couple of higher level tools virt-install & virt-manager. I'll
illustrate possible answers to your questions in terms of virsh...
> 1. Discovery : How does one find all processes running KVM vms ?
> ps -ef | grep qemu ?
libvirt doesn't expose the PIDs to app developers, but you can get a
list using
# export VIRSH_DEFAULT_CONNECT_URI=qemu:///system
# virsh list --all
Id Name State
----------------------------------
1 QEMUGuest1 running
- wizz shut off
> How does one know if qemu is using the kvm or not ?
# virsh dumpxml QEMUGuest1 | grep domain
The 'type' attribute will be one of qemu, kqemu, kvm
> 2. Identity : I am assuming that each VM is a process and pid would
> be an identifier, is there any other more unique identifier available.
libvirt provides 3 identifiers with different levels of uniqueness
1. 'id' - integer uniquely identifying amongst active guests on a host
2. 'name' - string uniquely identifying amongst active & inactive guests on a
host
3. 'uuid' - hex string uniquely identifying globally
> 3. Managing running processs :
> a. How does one connect to the manage the running vms ?
> I have read about screen and socat options.
> Both of these act as tty client, where success/failure and errors for a
> given
> command are very vague (parsing..). (A way to get return code for the
> operation
> would be great). Parsing ... command response and interpreting... is
> error prone.
> Say I choose socat, how do I gracefully detach from the console. ( other
> than
> just killing socat)
virsh provides a set of commands for controlling lifecycle & configuration
of the guest from the host machine, eg shutdown, start, pause, resume, suspend,
restore, dominfo, dumpxml, etc, etc
The graphical console is typically exposed with VNC / SDL. You can find the
VNC port with:
# virsh vncdisplay QEMUGuest1
:0
If you configured a serial port & setup the guest to start a getty on it
you can also connect via the 'serial console'
# virsh console QEMUGuest1
> b. How does one get the stats for the running VM ?
> 1. status : running, stopped, *migrating*..?
> 2. Current use of the memory : example allocated 1 GB, used 512 MB.
> 3. CPU : Effective cpu used ? Are vcpus supported ?
> /proc can be used... what about windows ? (when and if we have kvm
> on windows)
> 4. How much I/O and Network I/O
> 5. Wait times to get to I/O or CPU. (contention measures)
Can do the first 3 options
# virsh dominfo QEMUGuest1
Id: 1
Name: QEMUGuest1
UUID: c7a5fdbd-edaf-9455-926a-d65c16db1809
OS Type: hvm
State: running
CPU(s): 1
CPU time: 98.8s
Max memory: 219200 kB
Used memory: 219200 kB
We don't currently have APIs to show disk & network I/O stats. We also don't
yet provide migration support.
> 6. What is kvm_stats ? How to interpret its output?
No idea :-)
> c. Can one change memory, cpus, disks and networks on the fly for a
> running VM ? If so how ?
> This is critical for achiving dynamic resource management.
Not AFAIK. To be precise, libvirt provides APIs for that, but it requires better
guest support / paravirt device drivers. Also QEMU can do hot-add/remove of USB
devices.
> 4. Shutdown : How does one send command to VM to shutdown normally. I see
> only reset
> and powerdown commands only. Also, after shutdown, the image running in the
> machine
> shuts down, but the VM keeps running. Shouldnt the process also die ?
A controlled shutdown isn't provided by QEMU/KVM yet. One would need to simulate
some kind of ACPI power management support in the guest so it saw a virtual
software power button press i guess.
> 5. Snapshots : where are snapshots saved ? I tried savevm with /tmp/x, I was
> expecting a
> file containing memory image... do these work differrently ?
> Also, when one does loadvm, is the snapshot gone ? I mean can one restore
> the same
> snapshot multiple times ?
libvirt has APIs for snapshotting, but we've not implement them for QEMU
or KVM yet. You can save the file to any location you have write permissions
for. Its not a plain memory image because it also contains info about the
state of all the various virtual devices.
The snapshot doesn't deal with changes in state on your disks. So if you
restored
a snapshot, ran it for a while doing disk IO and then quit & tried to restore
the
snapshot again your disks would be out of sync.
That said if one could take snapshots of the disks (eg with LVM, or QCOW) then
it ought to be possible to use a snapshot multiple times over.
Dan.
--
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