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Re: [libvirt] [PATCH] docs: clarify that virsh setvcpus and setmem only work on active domains



On 13/01/2011, at 8:54 AM, Eric Blake wrote:
> On 01/12/2011 02:24 PM, Justin Clift wrote:
>> Addresses BZ # 622534:
>> 
>>  https://bugzilla.redhat.com/show_bug.cgi?id=622534
>> ---
>> tools/virsh.pod |   28 ++++++++++++++++++----------
>> 1 files changed, 18 insertions(+), 10 deletions(-)
>> 
>> diff --git a/tools/virsh.pod b/tools/virsh.pod
>> index 0e03d68..b4c6ff7 100644
>> --- a/tools/virsh.pod
>> +++ b/tools/virsh.pod
>> @@ -568,13 +568,16 @@ XEN_CREDIT scheduler and are now I<DEPRECATED>.
>> 
>> =item B<setmem> I<domain-id> B<kilobytes>
>> 
>> -Change the current memory allocation in the guest domain. This should take
>> -effect immediately. The memory limit is specified in
>> -kilobytes.
>> +Change the current memory allocation in an B<active> guest domain. This
>> +should take effect immediately.  The memory limit is specified in kilobytes.
> 
> Do we need extra text talking about rounding and/or rejection if the
> hypervisor can't support a memory limit with that small of a granularity
> (for example, Matthias recently posted patches regarding esx only having
> megabyte granularity).

That's not a bad idea.  I have no idea of the text to add about it though.  Is it
something you know, or should we ask Matthias, or ?


>> For Xen, you can only adjust the memory of a running domain if the
>> domain is paravirtualized or running the PV balloon driver.
>> 
>> +B<Note>, this command only works on active guest domains.  To change the
>> +number of virtual CPUs in a inactive guest domain, use the virsh B<edit>
>> +command to update the XML <memory> element.
> 
> Oops - don't you mean "change the memory allocation of an inactive"
> rather than "change the number of virtual CPUs in a inactive"?

Oh wow.  I even read that more than once, and still mentally missed it.  Will v2 it
after we figure out the rounding/rejection you mention above. :)



>> @@ -593,24 +596,29 @@ QEMU/KVM supports I<--hard-limit>, I<--soft-limit>, and I<--swap-hard-limit>.
>> =item B<setvcpus> I<domain-id> I<count> optional I<--maximum> I<--config>
>> I<--live>
> 
>> 
>> +B<Note>, this command only works on active guest domains.  To change the
>> +number of virtual CPUs in a inactive guest domain, use the virsh B<edit>
>> +command to update the XML <vcpu> element.
> 
> When I did the setvcpus work, my intention was that the --config option
> was to allow changing vcpu allocation without requiring a running
> domain, insofar as things are implemented by the hypervisor.  If we have
> cases where the behavior still doesn't match those intentions, we
> probably ought to fix the bugs, rather than documenting that this
> command is live-only.  So I'm thinking this paragraph doesn't belong.

Ahhh.  With the BZ, it's main intention is that people have tried running setvcpus
on an inactive domain, and it barfs.  I haven't actually tried the command to see
if modern libvirt behaves this way.


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