Re: [Xen-users] Purpose of mem-max command

Re: [Xen-users] Purpose of mem-max command

[Daniel Kiper]

On Tue, Oct 13, 2015 at 11:55:09AM +0100, Ian Campbell wrote:
> [CCing Daniel]
>
> Daniel, please could you advice on which Xen releases, guest types and
> guest kernel versions are currently expected to work with memory hotplug.

Well... It worked, regardless of guest type, when it was introduced first time.
At that time xend was Xen toolstack. Than xl appeared on the scene and it stopped
working. I tried to fix it but I was diverted to something more important. Last
time David (CC-ed here) fixed some memory hotplug issues in Linux kernel (please
check for-linus-4.4 branch in git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git
for more details). I suppose that he manged to overcome some xl deficiencies and
he will be able to shed some light what he did. If not or his work is not upstreamable
then I leave this on my TODO list. I hope that I will be able to work on this next
year. However, if somebody is up to this work I am able to mentor he/she or at
least review relevant patch series. Here are my old patches for xl:
http://lists.xen.org/archives/html/xen-devel/2013-04/msg03072.html This is really
old but I think it could be good starting point for further work.

Daniel

Re: [Xen-users] Purpose of mem-max command

[David Vrabel]

On 13/10/15 22:14, Daniel Kiper wrote:
> On Tue, Oct 13, 2015 at 11:55:09AM +0100, Ian Campbell wrote:
>> [CCing Daniel]
>>
>> Daniel, please could you advice on which Xen releases, guest types and
>> guest kernel versions are currently expected to work with memory hotplug.
> 
> Well... It worked, regardless of guest type, when it was introduced first time.
> At that time xend was Xen toolstack. Than xl appeared on the scene and it stopped
> working. I tried to fix it but I was diverted to something more important. Last
> time David (CC-ed here) fixed some memory hotplug issues in Linux kernel (please
> check for-linus-4.4 branch in git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git
> for more details). I suppose that he manged to overcome some xl deficiencies and
> he will be able to shed some light what he did. If not or his work is not upstreamable
> then I leave this on my TODO list. I hope that I will be able to work on this next
> year. However, if somebody is up to this work I am able to mentor he/she or at
> least review relevant patch series. Here are my old patches for xl:
> http://lists.xen.org/archives/html/xen-devel/2013-04/msg03072.html This is really
> old but I think it could be good starting point for further work.

I think I had to manually fiddle with xenstore keys to persuade xl to
allow mem-max to work as expected.

David

Re: [Xen-devel] Purpose of mem-max command

[Marco Guazzone]

On Wed, Oct 14, 2015 at 11:25 AM, David Vrabel <david.vrabel@citrix.com> wrote:
> On 13/10/15 22:14, Daniel Kiper wrote:
>> On Tue, Oct 13, 2015 at 11:55:09AM +0100, Ian Campbell wrote:
>>> [CCing Daniel]
>>>
>>> Daniel, please could you advice on which Xen releases, guest types and
>>> guest kernel versions are currently expected to work with memory hotplug.
>>
>> Well... It worked, regardless of guest type, when it was introduced first time.
>> At that time xend was Xen toolstack. Than xl appeared on the scene and it stopped
>> working. I tried to fix it but I was diverted to something more important. Last
>> time David (CC-ed here) fixed some memory hotplug issues in Linux kernel (please
>> check for-linus-4.4 branch in git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git
>> for more details). I suppose that he manged to overcome some xl deficiencies and
>> he will be able to shed some light what he did. If not or his work is not upstreamable
>> then I leave this on my TODO list. I hope that I will be able to work on this next
>> year. However, if somebody is up to this work I am able to mentor he/she or at
>> least review relevant patch series. Here are my old patches for xl:
>> http://lists.xen.org/archives/html/xen-devel/2013-04/msg03072.html This is really
>> old but I think it could be good starting point for further work.
>
> I think I had to manually fiddle with xenstore keys to persuade xl to
> allow mem-max to work as expected.
>
> David

Dear all,

Thank you very much for your replies.

Basically, AFAIU, hotplug fully worked with the old xen toolstack
while it only partially works with the xl toolstack.
Spceifically, with the xl toolstack (at least with version 4.4.3), we
are currently able to hotplug memory up and down with respect to the
statically configured maximum value (property "maxmem"), but we are
not able to dynamically increase/decrease the maximum value with "xl
mem-max" command.

Again, thank you very much for your help and your time.

Best,

Marco