CPUPOWER-MONITOR(1) cpupower Manual CPUPOWER-MONITOR(1)
NAME
cpupower-monitor - Report processor frequency and idle statistics
SYNOPSIS
cpupower monitor -l
cpupower monitor [-c][-m <mon1>,[<mon2>,...]] [-i seconds]
cpupower monitor [-c][-m <mon1>,[<mon2>,...]] command
DESCRIPTION
cpupower-monitor reports processor topology, frequency and idle power
state statistics. Either command is forked and statistics are printed
upon its completion, or statistics are printed periodically.
cpupower-monitor implements independent processor sleep state and fre-
quency counters. Some are retrieved from kernel statistics, some are
directly reading out hardware registers. Use -l to get an overview
which are supported on your system.
Options
-l
List available monitors on your system. Additional details about
each monitor are shown:
• The name in quotation marks which can be passed to the -m
parameter.
• The number of different counters the monitor supports in
brackets.
• The amount of time in seconds the counters might overflow,
due to implementation constraints.
• The name and a description of each counter and its proces-
sor hierarchy level coverage in square brackets:
• [T] -> Thread
• [C] -> Core
• [P] -> Processor Package (Socket)
• [M] -> Machine/Platform wide counter
-m <mon1>,<mon2>,...
Only display specific monitors. Use the monitor string(s) provided
by -l option.
-i seconds
Measure interval.
-c
Schedule the process on every core before starting and ending mea-
suring. This could be needed for the Idle_Stats monitor when no
other MSR based monitor (has to be run on the core that is mea-
sured) is run in parallel. This is to wake up the processors from
deeper sleep states and let the kernel re -account its cpuidle (C-
state) information before reading the cpuidle timings from sysfs.
command
Measure idle and frequency characteristics of an arbitrary com-
mand/workload. The executable command is forked and upon its exit,
statistics gathered since it was forked are displayed.
-v
Increase verbosity if the binary was compiled with the DEBUG option
set.
MONITOR DESCRIPTIONS
Idle_Stats
Shows statistics of the cpuidle kernel subsystem. Values are retrieved
from /sys/devices/system/cpu/cpu*/cpuidle/state*/. The kernel updates
these values every time an idle state is entered or left. Therefore
there can be some inaccuracy when cores are in an idle state for some
time when the measure starts or ends. In worst case it can happen that
one core stayed in an idle state for the whole measure time and the
idle state usage time as exported by the kernel did not get updated. In
this case a state residency of 0 percent is shown while it was 100.
Mperf
The name comes from the aperf/mperf (average and maximum) MSR registers
used which are available on recent X86 processors. It shows the average
frequency (including boost frequencies). The fact that on all recent
hardware the mperf timer stops ticking in any idle state it is also
used to show C0 (processor is active) and Cx (processor is in any sleep
state) times. These counters do not have the inaccuracy restrictions
the "Idle_Stats" counters may show. May work poorly on Linux-2.6.20
through 2.6.29, as the acpi-cpufreq kernel frequency driver periodi-
cally cleared aperf/mperf registers in those kernels.
Nehalem SandyBridge HaswellExtended
Intel Core and Package sleep state counters. Threads (hyperthreaded
cores) may not be able to enter deeper core states if its sibling is
utilized. Deepest package sleep states may in reality show up as ma-
chine/platform wide sleep states and can only be entered if all cores
are idle. Look up Intel manuals (some are provided in the References
section) for further details. The monitors are named after the CPU
family where the sleep state capabilities got introduced and may not
match exactly the CPU name of the platform. For example an IvyBridge
processor has sleep state capabilities which got introduced in Nehalem
and SandyBridge processor families. Thus on an IvyBridge processor one
will get Nehalem and SandyBridge sleep state monitors. HaswellExtended
extra package sleep state capabilities are available only in a specific
Haswell (family 0x45) and probably also other future processors.
Fam_12h Fam_14h
AMD laptop and desktop processor (family 12h and 14h) sleep state coun-
ters. The registers are accessed via PCI and therefore can still be
read out while cores have been offlined.
There is one special counter: NBP1 (North Bridge P1). This one always
returns 0 or 1, depending on whether the North Bridge P1 power state
got entered at least once during measure time. Being able to enter
NBP1 state also depends on graphics power management. Therefore this
counter can be used to verify whether the graphics' driver power man-
agement is working as expected.
EXAMPLES
cpupower monitor -l" may show:
Monitor "Mperf" (3 states) - Might overflow after 922000000 s
...
Monitor "Idle_Stats" (3 states) - Might overflow after 4294967295 s
...
cpupower monitor -m "Idle_Stats,Mperf" scp /tmp/test /nfs/tmp
Monitor the scp command, show both Mperf and Idle_Stats states counter
statistics, but in exchanged order.
Be careful that the typical command to fully utilize one CPU by doing:
cpupower monitor cat /dev/zero >/dev/null
Does not work as expected, because the measured output is redirected to
/dev/null. This could get workarounded by putting the line into an own,
tiny shell script. Hit CTRL-c to terminate the command and get the mea-
sure output displayed.
REFERENCES
"BIOS and Kernel Developer’s Guide (BKDG) for AMD Family 14h Proces-
sors" https://support.amd.com/us/Processor_TechDocs/43170.pdf
"Intel® Turbo Boost Technology in Intel® Core™ Microarchitecture (Ne-
halem) Based Processors" http://download.intel.com/design/processor/ap-
plnots/320354.pdf
"Intel® 64 and IA-32 Architectures Software Developer's Manual Volume
3B: System Programming Guide" https://www.intel.com/products/proces-
sor/manuals
FILES
/dev/cpu/*/msr
/sys/devices/system/cpu/cpu*/cpuidle/state*/.
SEE ALSO
powertop(8), msr(4), vmstat(8)
AUTHORS
Written by Thomas Renninger <trenn@suse.de>
Nehalem, SandyBridge monitors and command passing
based on turbostat.8 from Len Brown <len.brown@intel.com>
22/02/2011 CPUPOWER-MONITOR(1)
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