The Virtualization Cookbook for SLES 10 SP2 - z/VM - IBM

-/+ buffers/cache: 98 654
Swap: 761 0 761
► You can also give the memory back by echoing offline to the state file:
# echo offline > memory1/state
# echo offline > memory2/state
► Verify the memory has be returned:
# cat memory*/state
online
offline
offline
offline
# free -m
total used free shared buffers cached
Mem: 241 165 75 0 18 54
-/+ buffers/cache: 92 148
Swap: 761 0 761
This section has shown how to configure virtual machines with standby memory and how to
“hot-plug” the memory from Linux. Each of the four Linux virtual machines, LINUX01 -
LINUX04 default to 256 MB of memory and can be moved up to 1 GB. However, LINUX02 -
LINUX04 require Linux to be shutdown, the CP DEFINE STORAGE command to be run and Linux
to be rebooted. LINUX01 can now have memory added while Linux is running. This function
can increase your server farm’s performance and availability.
13.7 Utilizing the cpuplugd service
The cpuplugd service allows Linux to enable or disable CPUs and memory, based on a set
of rules. It can improve performance by setting the correct number of processors and amount
of memory for Linux systems depending on their current load. It can also prevent the Linux
scheduler from queue balancing in partial load situations.
More information on cpuplugd can be found in the manual Linux on System z Device Drivers,
Features and Commands on Red Hat Enterprise Linux 6 on the Web at
http://www.ibm.com/developerworks/linux/linux390/documentation_red_hat.html
13.7.1 Determining the virtual CPUs being used
To start work with cpuplugd, perform the following steps:
► Start an SSH session to a Linux and determine how many CPUs Linux has online. Write a
short bash script, lscpus, to save typing:
# cd /usr/local/sbin
# vi lscpus
#!/bin/bash
# script to list the number and status of virtual CPUs
for i in /sys/devices/system/cpu/cpu*
do
echo $i
cat $i/online
done
► Save the file and the set it to be executable:
# chmod +x lscpus
210 The Virtualization Cookbook for RHEL 6