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rohit pushed a commit to branch 4.18
in repository https://gitbox.apache.org/repos/asf/cloudstack-documentation.git
The following commit(s) were added to refs/heads/4.18 by this push:
new 0919754 hosts: make it clear what to expect and how to configure
balloon feature on KVM (#337)
0919754 is described below
commit 0919754ab51fbff6c2732f0fbfbff3bfd9219e69
Author: Rohit Yadav <[email protected]>
AuthorDate: Fri Aug 4 16:00:40 2023 +0530
hosts: make it clear what to expect and how to configure balloon feature on
KVM (#337)
Signed-off-by: Rohit Yadav <[email protected]>
---
source/adminguide/hosts.rst | 42 ++++++++++++++++++++++++++++++++++++++----
1 file changed, 38 insertions(+), 4 deletions(-)
diff --git a/source/adminguide/hosts.rst b/source/adminguide/hosts.rst
index 9a593fd..1ef6df2 100644
--- a/source/adminguide/hosts.rst
+++ b/source/adminguide/hosts.rst
@@ -377,10 +377,11 @@ VMware tools installed.
KVM
'''
-All VMs are required to support the virtio drivers. These drivers are
+All KVM VMs are required to support the virtio drivers. These drivers are
installed in all Linux kernel versions 2.6.25 and greater. The
administrator must set CONFIG\_VIRTIO\_BALLOON=y in the virtio
-configuration.
+configuration. Drivers for Windows can be downloaded from
+https://github.com/virtio-win/virtio-win-pkg-scripts
Hypervisor capability
@@ -396,12 +397,45 @@ The DMC (Dynamic Memory Control) capability of the
hypervisor should be
enabled. Only XenServer Advanced and above versions have this feature.
-VMware, KVM
-'''''''''''
+VMware
+''''''
Memory ballooning is supported by default.
+KVM
+'''
+
+Memory ballooning is supported and enabled by default. This can be configured
on
+per KVM host basis via the `vm.memballoon.disable=false` property and the
+`vm.memballoon.stats.period` property in the `agent.properties` of the KVM
host.
+
+The memory ballooning feature on KVM allows the host to reclaim memory from
+guest VMs which is enabled by a virtio balloon device on the guest VM and the
+related virtio drivers inside the guest VMs. This feature is mainly intended to
+support over-committing memory on KVM hosts.
+
+A related feature, KSM (Kernel Same-page Merging), can also be enabled to
assist
+with over-committing memory. On some distributions such as Ubuntu, this is
+enabled by default, and can be checked otherwise by checking/setting
+`/sys/kernel/mm/ksm/run` to 1 and for libvirt set the `KSM_ENABLED=AUTO` in
+`/etc/defaults/qemu-kvm`.
+
+Note: the memory ballooning feature isn't automatic on KVM and shouldn't be
+confused with the dynamic scaling feature that allows manual scaling of running
+VMs by changing the service offering (feature can be enabled via the setting
+enable.dynamic.scale.vm) of VMs that aren't using a fixed compute offering.
+
+By default, when memory is over provisioned (setting
mem.overprovisioning.factor
+is greater than 1.0 at global or cluster level) the actual memory for the VM is
+the memory per the service offering divided by the global or cluster-specific
+memory overprovisioning factor. This means guests start with a lower memory
than
+their service offering intended memory, which will not be changed or scaled
+automatically. When overcommitting memory, this behaviour can be disabled by
+turning off (set the value false) the setting
+`vm.min.memory.equals.memory.divided.by.mem.overprovisioning.factor`.
+
+
Setting Over-Provisioning Factors
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
