Information Technology Reference
In-Depth Information
The Logical Domains technology provides a policy-based resource manager that
automatically adds or removes CPUs from a running domain based on its utili-
zation and relative priority. Policies can be prioritized to ensure that important
domains obtain preferential access to resources. They can also be enabled or dis-
abled manually or based on time of day for different prime shift and off-hours poli-
cies. For example, one domain may have the highest resource needs and priority
during the daytime, while a domain running batch work may operate in a more
resource-intensive manner at night.
Policy rules specify the number of CPUs that a domain has, bounded by mini-
mum and maximum values, and based on their utilization:
The number of CPUs is adjusted between
vcpu-min
and
vcpu-max
based on
util-upper
and
util-lower
CPU busy percentages. (All of these variables
are property values associated with the policy.)
■
If CPU utilization exceeds the value of
util-upper
, virtual CPUs are added
to the domain until the number is between
vcpu-min
and
vcpu-max
.
■
If the utilization drops below
util-lower
, virtual CPUs are removed from
the domain until the number is between
vcpu-min
and
vcpu-max
.
■
If
vcpu-min
is reached, no more virtual CPUs can be dynamically removed.
If
vcpu-max
is reached, no more virtual CPUs can be dynamically added.
Manual changes to the number of CPUs can still be made using the
ldm
com-
mands shown previously.
■
Multiple policies can be in effect, and are optionally controlled by
tod-begin
and
tod-end
(time of day) values.
■
The resource manager includes ramp-up (attack) and ramp-down (decay) con-
trols to adjust the system's response to workload changes, specifying the number
of CPUs to add or remove based on changes in utilization, and how quickly the
resource manager responds. Resource management is disabled in elastic power
management mode, in which unused CPUs are powered down to reduce power
consumption. The following is an example of a command creating a policy:
#
ldm add-policy tod-begin=09:00 tod-end=18:00 util-lower=25 \
util-upper=75 vcpu-min=2 vcpu-max=16 attack=1 \
decay=1 priority=1 name=high-usage ldom1
This policy controls the number of CPUs for domain
ldom1
, is named
high-us-
age
, and is in effect between 9
A
.
M
. and 6
P
.
M
. The lower and upper CPU utilization
settings are 25% and 75% CPU busy, respectively. The number of CPUs is adjusted
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