Sample configuration file

Ubuntu 22.04 LTS LPAR mode z/VM guest KVM guest

A typical configuration file includes multiple user-defined variables and values from procfs, for example, to calculate the page scan rate or the cache size.

Figure 1. Sample configuration file for Linux on z/VM with CPU and memory hotplug

# Required static variables

CPU_MIN="1"
CPU_MAX="0"
UPDATE="1"
CMM_MIN="0"
CMM_MAX="131072"	# 512 MB

# User-defined variables

pgscan_d="vmstat.pgscan_direct_dma[0] + vmstat.pgscan_direct_normal[0] + vmstat.pgscan_direct_movable[0]"
pgscan_d1="vmstat.pgscan_direct_dma[1] + vmstat.pgscan_direct_normal[1] + vmstat.pgscan_direct_movable[1]"
# page scan rate in pages / timer tick
pgscanrate="(pgscan_d - pgscan_d1) / (cpustat.total_ticks[0] - cpustat.total_ticks[1])"
# cache usage in kilobytes
avail_cache="meminfo.Cached - meminfo.Shmem"

user_0="(cpustat.user[0] - cpustat.user[1])"
nice_0="(cpustat.nice[0] - cpustat.nice[1])"
system_0="(cpustat.system[0] - cpustat.system[1])"
user_2="(cpustat.user[2] - cpustat.user[3])"
nice_2="(cpustat.nice[2] - cpustat.nice[3])"
system_2="(cpustat.system[2] - cpustat.system[3])"
CP_Active0="(user_0 + nice_0 + system_0) / (cpustat.total_ticks[0] - cpustat.total_ticks[1])"
CP_Active2="(user_2 + nice_2 + system_2) / (cpustat.total_ticks[2] - cpustat.total_ticks[3])"
CP_ActiveAVG="(CP_Active0+CP_Active2) / 2"

idle_0="(cpustat.idle[0] - cpustat.idle[1])"
iowait_0="(cpustat.iowait[0] - cpustat.iowait[1])"
idle_2="(cpustat.idle[2] - cpustat.idle[3])"
iowait_2="(cpustat.iowait[2] - cpustat.iowait[3])"
CP_idle0="(idle_0 + iowait_0) / (cpustat.total_ticks[0] - cpustat.total_ticks[1])"
CP_idle2="(idle_2 + iowait_2) / (cpustat.total_ticks[2] - cpustat.total_ticks[3])"
CP_idleAVG="(CP_idle0 + CP_idle2) / 2"

# More required variables

# cmm_inc: 10% of free memory, in 4K pages
CMM_INC="meminfo.MemFree / 40"
# cmm_dec: 10% of total memory, in 4K pages
CMM_DEC="meminfo.MemTotal / 40"

# Hotplug rules
HOTPLUG="((1 - CP_ActiveAVG) * onumcpus) < 0.08"
HOTUNPLUG="(CP_idleAVG * onumcpus) > 1.15"
MEMPLUG="pgscanrate > 20"
MEMUNPLUG="(meminfo.MemFree + avail_cache) > (meminfo.MemTotal / 10)"

Attention: These configuration file samples illustrate the syntax of the configuration file. Useful rules might differ considerably, depending on the workload, resources, and requirements of the system for which they are designed.

After you install cpuplugd, a commented sample configuration file is available at /etc/cpuplugd.conf.