Re: CVS commit: src/sys/arch

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

Andrew Doran wrote:
> Module Name:    src
> Committed By:   ad
> Date:           Sat May 10 16:12:33 UTC 2008
>
> Modified Files:
>         src/sys/arch/amd64/amd64: amd64func.S autoconf.c cpufunc.S genassym.cf
>             identcpu.c ipifuncs.c procfs_machdep.c
>         src/sys/arch/amd64/include: cpu.h
>         src/sys/arch/i386/i386: autoconf.c cpufunc.S genassym.cf i386func.S
>             identcpu.c ipifuncs.c pmc.c powernow_k7.c procfs_machdep.c
>         src/sys/arch/i386/include: cpu.h
>         src/sys/arch/x86/include: cpu_counter.h
>         src/sys/arch/x86/isa: clock.c
>         src/sys/arch/x86/x86: cpu.c tsc.c tsc.h
>
> Log Message:
> Improve x86 tsc handling:
>
> - Ditch the cross-CPU calibration stuff. It didn't work properly, and it's
>   near impossible to synchronize the CPUs in a running system, because bus
>   traffic will interfere with any calibration attempt, messing up the
>   timings.
>
> - Only enable the TSC on CPUs where we are sure it does not drift. If we are
>   On a known good CPU, give the TSC high timecounter quality, making it the
>   default.
>
> - When booting CPUs, detect TSC skew and account for it. Most Intel MP
>   systems have synchronized counters, but that need not be true if the
>   system has a complicated bus structure. As far as I know, AMD systems
>   do not have synchronized TSCs and so we need to handle skew.

This is true for AMD K8 (Family 0xf) and AMD Griffin (Family 0x11).
AMD Barcelona/Phenom (Family 0x10) synchronizes their TSC with the 
memory clock which always runs at a fixed speed. On those systems you
need synchonrize the memory clock between the memory controller.
On each socket, there's one memory controller.

> - While an AP is waiting to be set running, try and make the TSC drift by
>   entering a reduced power state. If we detect drift, ensure that the TSC
>   does not get a high timecounter quality. This should not happen and is
>   only for safety.
>
> - Make cpu_counter() stuff LKM safe.