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CORECSTAT(4)          DragonFly Kernel Interfaces Manual          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

     The corecstat driver was written by Imre Vadasz <imre@vdsz.com>.

DragonFly 6.5-DEVELOPMENT      January 24, 2026      DragonFly 6.5-DEVELOPMENT

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