Writing Device Drivers

Kernel Statistics Structures

The structures for the different kinds of kstats are:


Each kernel statistic (kstat) that is exported by device drivers consists of a header section and a data section. The kstat(9S) structure is the header portion of the statistic.


Structure for interrupt kstats. The types of interrupts are:

  • Hard interrupt – Sourced from the hardware device itself

  • Soft interrupt – Induced by the system through the use of some system interrupt source

  • Watchdog interrupt – Induced by a periodic timer call

  • Spurious interrupt – An interrupt entry point was entered but there was no interrupt to service

  • Multiple service – An interrupt was detected and serviced just prior to returning from any of the other types

Drivers generally report only claimed hard interrupts and soft interrupts from their handlers, but measurement of the spurious class of interrupts is useful for auto-vectored devices to locate any interrupt latency problems in a particular system configuration. Devices that have more than one interrupt of the same type should use multiple structures.


Structure for I/O kstats.


Structure for named kstats. A named kstat is an array of name-value pairs. These pairs are kept in the kstat_named structure.