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Re: [libvirt] [PATCH] virsh: Fix docs for "virsh setmaxmem"

On 03/22/13 22:01, Eric Blake wrote:
On 03/22/2013 04:08 AM, Peter Krempa wrote:
The docs assumed the command works always for QEMU and other
hypervisors. Unfortunately until qemu will add memory hotplug
this can't be done. Fix the docs to mention this limitation.

The setmaxmem command controls balloon size, not memory hotplug.  If
qemu adds memory hotplug, we STILL have to pre-declare a maximum memory
size when qemu first boots, and at runtime, you can only change the
current memory.  And if we do add qemu memory hotplug support (and not
just memory ballooning), I'm not sure if it would make sense to reuse
the setmaxmem command (probably with a new flag) or add a new command.

I agree, the commit message was a bit misleading. The question of memory hotplug will have to remain open until qemu will actually support it. I removed the note about hotplug from the commit message.

  tools/virsh.pod | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

-This command works for at least the Xen, QEMU/KVM and vSphere/ESX hypervisors.
+Some hypervisors such as QEMU/KVM don't support live changes (especially
+increasing) of the maximum memory limit.

I don't know of any hypervisor that supports changing the maximum limit
on a live domain - the maximum is pinned when the hypervisor starts, and
can only be changed for the next boot.

At any rate, while this wording might not be the best possible, it is
certainly an improvement, so:

Well yes. I thought about it a bit more, the wording isn't ideal but definitely better than it was before, so ...


I pushed this patch. Thanks.


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