[Users] hot add ram to a vm

[Sander Grendelman]

On Fri, Dec 13, 2013 at 1:42 PM, Michal Skrivanek
<michal.skrivanek at 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.

Example from the xml definition:

  <memory unit='KiB'>3145728</memory>
  <currentMemory unit='KiB'>1048576</currentMemory>

After booting:

[root at 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 at 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 at grkvm201 ~]#

memory increased to 2GB through virt-manager:

[root at 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 at 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 at 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 at grkvm201 ~]#