RFC: New event timers infrastructure
Alexander Motin <mav <at> FreeBSD.org>
2010-06-06 22:02:12 GMT
Most of x86 systems now has at least 4 types of event timers: i8254,
RTC, LAPIC and HPET. Respective code in kernel is very tangled, heavily
hardcoded and absolutely not scalable. I have reimplemented it, trying
to solve these issues.
I did such things:
- created unified timer driver's API (sys/timeet.h, kernel/kern_et.c).
It supports global and per-CPU timers, periodic and one-shot. Provides
driver and consumer interfaces for choosing timers and operating them;
- cleaned existing x86 event timer driver's code and modified it for
new API (x86/isa/atrtc.c, x86/isa/clock.c, x86/x86/local_apic.c). LAPIC
timer is now per-CPU and supports both periodic and one-shot modes;
- extended HPET driver to support it's event timers in periodic and
one-shot mode (dev/acpica/acpi_hpet.c). Support for per-CPU operation
and FSB interrupts planned for later;
- written mostly machine-independent mid-layer for managing any present
timers to provide clocks needed for kernel (x86/x86/timeevents.c). It
supports both global and per-CPU timers. Now it supports only periodic
mode, but one-shot mode support planned for later.
All this stuff deeply configurable via both loader tunables on boot and
sysctls in real time:
kern.eventtimer.choice: LAPIC(500) HPET(400) HPET1(390) HPET2(390)