Advanced Programmable Interrupt Controller (APIC)
This driver is a mandatory part of amd64 kernel. To compile this driver into
i386 kernel, place the following line in your kernel configuration file:
The following tunable is settable from the
- controls event timers functionality support. Setting to 0, disables it.
Default value is 1.
- Set this to 1 to disable APIC support, falling back to the legacy
There are two components in the Intel APIC system, the local APIC (LAPIC) and
the I/O APIC. There is one local APIC in each CPU in the system. There is
typically one I/O APIC for each peripheral bus in the system.
Local APICs manage all external interrupts for a specific processor. In
addition, they are able to accept and generate inter-processor interrupts
I/O APICs contain a redirection table, which is used to route the interrupts
they receive from peripheral buses to one or more local APICs.
Each local APIC includes one 32-bit programmable timer. This driver uses them to
supply kernel with one event timer named "LAPIC". Event timer
provided by the driver supports both one-shot an periodic modes. Because of
local APIC nature it is per-CPU. The timer frequency is not reported by the
platform and so automatically measured by the driver on the first use.
Depending on CPU model this timer may stop in C3 and deeper CPU sleep states.
Driver automatically adjusts event timer priority and reports it to prevent
entering dangerous sleep states when it is used.