Re: Increasing domain memory beyond initial maxmem

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Tue, Apr 05, 2022 at 01:03:57PM +0200, Juergen Gross wrote:
> Hi Marek,
> 
> On 31.03.22 14:36, Marek Marczykowski-Górecki wrote:
> > On Thu, Mar 31, 2022 at 02:22:03PM +0200, Juergen Gross wrote:
> > > Maybe some kernel config differences, or other udev rules (memory onlining
> > > is done via udev in my guest)?
> > > 
> > > I'm seeing:
> > > 
> > > # zgrep MEMORY_HOTPLUG /proc/config.gz
> > > CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG=y
> > > CONFIG_MEMORY_HOTPLUG=y
> > > # CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE is not set
> > > CONFIG_XEN_BALLOON_MEMORY_HOTPLUG=y
> > > CONFIG_XEN_MEMORY_HOTPLUG_LIMIT=512
> > 
> > I have:
> > # zgrep MEMORY_HOTPLUG /proc/config.gz
> > CONFIG_ARCH_ENABLE_MEMORY_HOTPLUG=y
> > CONFIG_MEMORY_HOTPLUG=y
> > CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=y
> > CONFIG_XEN_BALLOON_MEMORY_HOTPLUG=y
> > CONFIG_XEN_MEMORY_HOTPLUG_LIMIT=512
> > 
> > Not sure if relevant, but I also have:
> > CONFIG_XEN_UNPOPULATED_ALLOC=y
> > 
> > on top of that, I have a similar udev rule too:
> > 
> > SUBSYSTEM=="memory", ACTION=="add", ATTR{state}=="offline", ATTR{state}="online"
> > 
> > But I don't think they are conflicting.
> > 
> > > What type of guest are you using? Mine was a PVH guest.
> > 
> > PVH here too.
> 
> Would you like to try the attached patch? It seemed to work for me.

Unfortunately it doesn't help, now the behavior is different:

Initially guest started with 800M:

    [root@personal ~]# free -m
                  total        used        free      shared  buff/cache   available
    Mem:            740         223         272           2         243         401
    Swap:          1023           0        1023

Then increased:

    [root@dom0 ~]$ xl mem-max personal 2048
    [root@dom0 ~]$ xenstore-write /local/domain/$(xl domid personal)/memory/static-max $((2048*1024))
    [root@dom0 ~]$ xl mem-set personal 2000

And guest shows now only a little more memory, but not full 2000M:

    [root@personal ~]# [   37.657046] xen:balloon: Populating new zone
    [   37.658206] Fallback order for Node 0: 0 
    [   37.658219] Built 1 zonelists, mobility grouping on.  Total pages: 175889
    [   37.658233] Policy zone: Normal

    [root@personal ~]# 
    [root@personal ~]# free -m
                  total        used        free      shared  buff/cache   available
    Mem:            826         245         337           2         244         462
    Swap:          1023           0        1023


I've applied the patch on top of 5.16.18. If you think 5.17 would make a
difference, I can try that too.


-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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