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

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

[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.

Thanks,

Ian.

On Mon, 2015-10-12 at 21:14 +0200, Marco Guazzone wrote:
> On Mon, Oct 12, 2015 at 7:45 PM, Simon Hobson <linux@xxxxxxxxxxxxxxxx> wrote:
> > Marco Guazzone <marco.guazzone@xxxxxxxxx> wrote:
> > 
> > > Hmmm. It seems it does not work in my case since I get an ERROR from Xen.
> > 
> > Does your guest OS support memory hotplug ?
> > As described by others, if your guest does not support memory hotplug,
> > then you can only ballon guest memory up to the amount specified as max
> > -mem at startup time. Only if you have hotplug support can you "hot
> > plug" extra memory into the guest system over and above what was
> > configured as max-mem at startup time.
> > 
> 
> My host system:
> - Fedora Linux 21 x86_64
> - kernel: 4.1.8-100
> - Xen: 4.4.3-4
> 
> My guest system:
> - CentOS Linux 7.1.1503 (Core)  x86_64
> - kernel: 3.10.0-229.14.1
> 
> I think the guest OS support mem hotplug since I can see the related
> sysfs files in /sys/devices/system/memory/.
> For instance:
> $ grep -r --include="state" "line" /sys/devices/system/memory/
> /sys/devices/system/memory/memory0/state:online
> /sys/devices/system/memory/memory1/state:online
> /sys/devices/system/memory/memory2/state:online
> /sys/devices/system/memory/memory3/state:online
> ...
> /sys/devices/system/memory/memory65/state:online
> 
> But if you know any other practical check, please tell me.
> 
> Meanwhile, I've tried  to increase RAM again, from 8g to 10g:
> $ xl mem-max memtest 10g
> 
> Then I've checked if something is changed in sysfs (the hope was at
> least to see new memory marked as offline).
> But nothing has changed. I see tha same memory banks (from 0 to 65)
> And if I try to set 9GB of RAM I got the same error as before:
> $ xl mem-set memtest 9g
> libxl: error: libxl.c:4104:libxl_set_memory_target: memory_dynamic_max
> must be less than or equal to memory_static_max
> 
> If you know a linux distribution where hotplug works for sure I can
> try to create a VM with that OS
> 
> Thank you so much.
> 
> Marco
> 
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