4:41 p.m.
----- Original Message -----
From: "Andrew Cathrow" <acathrow(a)redhat.com>
To: "Sander Grendelman" <sander(a)grendelman.com>
Cc: users(a)ovirt.org
Sent: Monday, December 16, 2013 2:05:00 PM
Subject: Re: [Users] hot add ram to a vm
----- Original Message -----
> From: "Sander Grendelman" <sander(a)grendelman.com>
> To: "Michal Skrivanek" <michal.skrivanek(a)redhat.com>
> Cc: users(a)ovirt.org
> Sent: Friday, December 13, 2013 8:52:42 AM
> Subject: Re: [Users] hot add ram to a vm
>
> On Fri, Dec 13, 2013 at 1:42 PM, Michal Skrivanek
> <michal.skrivanek(a)redhat.com> wrote:
> > Too bad QEMU doesn't support it. So it's still a long way.
>
> qemu/libvirt "kind of" supports it (at least in F19).
>
> In virt-manager you can define "current" and "maximum" memory
> allocation.
>
> The VM only sees the current allocation and you can hot add memory up
> to the maximum allocation.
It isn't really hot-plug.
This allows you to statically set the physical ram but then use the balloon
device to "borrow" some ram from the guest.
If max memory was 4gb and we set current memory to 2gb the VM would still see
4gb of physical memory but the balloon driver would be taking up 2gb of
memory in the guest, this memory would be returned to the host for other VMs
to use.
Right, currentMemory is how you manipulate the balloon:
http://libvirt.org/formatdomain.html#elementsMemoryAllocation
Note that is requires an agent, a driver and cooperation from the guest.
>
> Example from the xml definition:
>
> <memory unit='KiB'>3145728</memory>
> <currentMemory unit='KiB'>1048576</currentMemory>
>
> After booting:
>
> [root@grkvm201 ~]# uname -a
> Linux grkvm201.plusine.intern 2.6.32-358.23.2.el6.x86_64 #1 SMP Wed
> Oct 16 18:37:12 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
> [root@grkvm201 ~]# free -lm
> total used free shared buffers
> cached
> Mem: 837 296 540 0 8
> 84
> Low: 837 296 540
> High: 0 0 0
> -/+ buffers/cache: 203 634
> Swap: 511 0 511
> [root@grkvm201 ~]#
>
> memory increased to 2GB through virt-manager:
>
> [root@grkvm201 ~]# free -lm
> total used free shared buffers
> cached
> Mem: 1861 295 1565 0 8
> 84
> Low: 1861 295 1565
> High: 0 0 0
> -/+ buffers/cache: 202 1659
> Swap: 511 0 511
> [root@grkvm201 ~]# cat /proc/meminfo
> MemTotal: 1906176 kB
> MemFree: 1603456 kB
> Buffers: 9140 kB
> Cached: 86860 kB
> SwapCached: 0 kB
> Active: 92564 kB
> Inactive: 68064 kB
> Active(anon): 68692 kB
> Inactive(anon): 12 kB
> Active(file): 23872 kB
> Inactive(file): 68052 kB
> Unevictable: 21600 kB
> Mlocked: 11380 kB
> SwapTotal: 524280 kB
> SwapFree: 524280 kB
> Dirty: 12 kB
> Writeback: 0 kB
> AnonPages: 86232 kB
> Mapped: 20436 kB
> Shmem: 288 kB
> Slab: 75132 kB
> SReclaimable: 14576 kB
> SUnreclaim: 60556 kB
> KernelStack: 1464 kB
> PageTables: 4224 kB
> NFS_Unstable: 0 kB
> Bounce: 0 kB
> WritebackTmp: 0 kB
> CommitLimit: 1477368 kB
> Committed_AS: 547624 kB
> VmallocTotal: 34359738367 kB
> VmallocUsed: 20040 kB
> VmallocChunk: 34359688500 kB
> HardwareCorrupted: 0 kB
> AnonHugePages: 18432 kB
> HugePages_Total: 0
> HugePages_Free: 0
> HugePages_Rsvd: 0
>
> Memory decreased to 1,5GB through virt-manager:
> [root@grkvm201 ~]# free -lm
> total used free shared buffers
> cached
> Mem: 1349 295 1054 0 8
> 84
> Low: 1349 295 1054
> High: 0 0 0
> -/+ buffers/cache: 201 1147
> Swap: 511 0 511
> [root@grkvm201 ~]#
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