RFC Trace Clock v2

Hi,

I've cleaned up the LTTng timestamping code, renamed it into "trace clock", ripped apart the tsc_sync.c x86 code, added documentation (printk to the console when the tracing clock is used) about what to do when an unsync TSC is detected. I however kept the cache-line bouncing workaround for now. However, I now synchronize the counters every jiffy with a per-cpu timer so it gives an upper bound to the time imprecision.

The trace clock works with a trace_clock_get()/put(), so all the mechanic and overhead that might be required to provide correct timestamps on weird systems is *only* enabled when tracing is active.

I plan to stick to this simple solution for now so we can get reliable tracing for 95ish% of systems out there, and to keep room for improvement (nice NTP-like schemes) for a later version. (sadly, given this is actually v2, I cannot say "let's keep that for v2") ;)

This patchset applies on top of 2.6.28-rc3.

Mathieu

Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68