TSC Timecounter and multi-core/SMP

[gnn at freebsd.org]

At Fri, 11 Apr 2008 08:34:29 -0400 (EDT),
Andrew Gallatin wrote:
> 
> 
> gnn at freebsd.org writes:
>  > Howdy,
>  > 
>  > Is the TSC timecounter synchronized across multiple cores and/or
>  > processors?  A quick search seems to indicate it's not but I'd like to
>  > find a definitive reference on the TSC.
> 
> There is a great comment in the OpenSolaris source code talking about
> TSCs and their behavior on SMP systems.  See
> http://cvs.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/i86pc/os/timestamp.c
> 

Actually this was a very helpful bit of reading.

I also believe that at least per processor there is only 1 TSC, that
is, on a 2 or 4 core, all cores share the same TSC.

Best,
George