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Install

Worked for

  • dom0 2.6.21.7-5.fc8xen #1 SMP Thu Aug 7 12:44:22 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux
AMD Opteron(tm) Processor 848
flags: fpu tsc msr pae mce cx8 apic mtrr mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext lm 3dnowext 3dnow up
    • domU 32b works
    • domU 64b works

Memory Ballooning

32 bit guest

Original guest was 1G. Test was: 

virsh shutdown f11
virsh dumpxml f11 > f11.xml
  • Add currentMemory parameter which defines minimum memory given to guest at boot.
<memory>1048576</memory>
<currentMemory>524288</currentMemory>
  • Enact this guest config in Xen via libvirt.
virsh define f11.xml
virsh start f11

See: QA_talk:Testcase_Virtualization_XenDomU_Memory_Ballooning

Balloon Up - fail?

[root@felix tmp]# grep -i memory f11-32.xml
  <memory>1048576</memory>
  <currentMemory>524288</currentMemory>

# guest is running...
[root@felix xen]# virsh setmem f11-32 $(( 1024 * 1000 ))

[root@felix tmp]# grep 'memory target' /var/log/xen/xend.log |tail -1
[2009-05-06 23:24:23 28390] DEBUG (XendDomainInfo:664) Setting memory target of domain f11-32 (7) to 1000 MiB.

[root@felix xen]# virsh dominfo f11-32 | grep memory
Max memory:     1048576 kB
Used memory:    524288 kB

After few minutes guest free -m still reports 519.

Balloon Down - PASS

[root@felix tmp]# virsh setmem f11-32 $(( 1024 * 256 ))

[root@felix tmp]# grep 'memory target' /var/log/xen/xend.log |tail -1
[2009-05-06 23:36:08 28390] DEBUG (XendDomainInfo:664) Setting memory target of domain f11-32 (7) to 256 MiB.

[root@felix tmp]# virsh dominfo f11-32|grep memory
Max memory:     1048576 kB
Used memory:    262144 kB

Guest free -m reports 256.

Balloon Back Up - PASS

Apparently I'm mistaken in my understanding of <memory> and <currentMemory> tags. I was not able to balloon above 519. 

[root@felix tmp]# virsh setmem f11-32 $(( 1024 * 1000 ))

[root@felix tmp]# grep 'memory target' /var/log/xen/xend.log |tail -1
[2009-05-06 23:40:04 28390] DEBUG (XendDomainInfo:664) Setting memory target of domain f11-32 (7) to 1000 MiB.
[root@felix tmp]# virsh dominfo f11-32|grep memory
Max memory:     1048576 kB
Used memory:    524288 kB

Guest free -m reports 519 again.

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