CORECSTAT(4)

NAME
corecstat - device driver for Intel Core C-State and Package C-State residency counters.

SYNOPSIS
To compile this driver into the kernel, place the following line in your kernel configuration file:

device corecstat

Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):

    corecstat_load="YES"

DESCRIPTION
The corecstat driver provides support for Intel's Core C-State and Package C-State residency counters, that are provided in Nehalem and newer Core and Xeon CPUs, as well as in Atom CPUs of the Silvermont and newer architectures. Core C-State residency is shown for each physical CPU core, and Package C-State residency is shown per CPU package. The values are exposed through the HW_SENSORS sysctl(3) tree. For example:

    % sysctl hw.sensors
    hw.sensors.cpu2.percent0: 0.00% (node0 core0 C3 res.)
    hw.sensors.cpu2.percent1: 0.00% (node0 core0 C6 res.)
    hw.sensors.cpu2.percent2: 99.42% (node0 core0 C7 res.)
    hw.sensors.cpu3.percent0: 0.00% (node0 core1 C3 res.)
    hw.sensors.cpu3.percent1: 0.00% (node0 core1 C6 res.)
    hw.sensors.cpu3.percent2: 99.62% (node0 core1 C7 res.)
    hw.sensors.cpu_node0.percent0: 14.33% (node0 PC2 residency)
    hw.sensors.cpu_node0.percent1: 0.03% (node0 PC3 residency)
    hw.sensors.cpu_node0.percent2: 0.00% (node0 PC6 residency)
    hw.sensors.cpu_node0.percent3: 85.18% (node0 PC7 residency)
    hw.sensors.cpu_node0.percent4: 0.00% (node0 PC8 residency)
    hw.sensors.cpu_node0.percent5: 0.00% (node0 PC9 residency)
    hw.sensors.cpu_node0.percent6: 0.00% (node0 PC10 residency)

These numbers are useful to understand how much, and to what extent CPU powersaving is being used. Higher numbers designate a "deeper" powersaving state, which will use less electricity. However "deeper" powersaving states will also include a slower wakeup time, which can sometimes degrade interactive performance under partial system load. You can modify the C-State powersaving behavior on these Intel CPUs by adjusting the machdep.mwait.CX sysctl knobs.

SEE ALSO
systat(1), sysctl(3), coretemp(4), corepower(4), devctl(4), devd(8), sensorsd(8), sysctl(8)

HISTORY
The corecstat driver first appeared in DragonFly 6.5.

AUTHORS
-nosplit The corecstat driver was written by Imre Vadász <imre@vdsz.com>.