Re: TSC Timecounter and multi-core/SMP

From: Andrew Gallatin <gallatin_at_cs.duke.edu>
Date: Fri, 11 Apr 2008 08:34:29 -0400 (EDT)
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

FWIW, solaris manages to keep track of unsynchronized TSCs, and use
unsynchronized TSC timecounters for timekeeping on SMP systems.  It
would be nice if FreeBSD could do the same.

Drew
Received on Fri Apr 11 2008 - 10:34:59 UTC

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